Winnipeg Forest Watch Handbook

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Winnipeg Forest Watch Handbook

A Guide on Tree Health and Basic Tree Care for Homeowners

TREES Winnipeg The Coalition to Save the Elms

Winnipeg Forest Watch Handbook A Guide on Tree Health and Basic Tree Care for Homeowners

Trees Winnipeg (Coalition to Save the Elms) Winnipeg, Canada, 2012

To request copies of this publication, please contact: Trees Winnipeg (Coalition to Save the Elms) 1539 Waverley Street Winnipeg, Manitoba R3T 4V7 Phone: (204) 832-7188 Email:

Table of Contents How to Use this Guide .............................................. ii Introduction................................................................. 1 Trees Winnipeg: Our Roots and How we’re Growing! .................................................................... 1 The Need for Tree Protection ................................ 4 The Importance of Community Involvement ..... 4 Winnipeg Forest Watch ........................................... 5 Red Alert! Invasive Tree Pests ................................ 7 Dutch Elm Disease................................................... 7 Emerald Ash Borer................................................... 9 Asian Longhorn Beetle .......................................... 11 Gypsy Moth ............................................................. 13 Urban Forest Pests and Diseases.......................... 15 Leaves and Canopy ................................................ 15 Fruits, Blossoms & Twigs ..................................... 27 Main Trunk & Branches ........................................ 31 Basic Tree Care ......................................................... 36 Tree Planting........................................................... 36 Staking ..................................................................... 38 Soils and Mulching ................................................ 39 Pruning .................................................................... 39 Treating Wounds.................................................... 42 Watering .................................................................. 42 Fertilizing ................................................................ 43 Winter Protection................................................... 43 How to Hire an Arborist ....................................... 44 Tree Identification ................................................... 45 Illustrated Terms ................................................... 45 Deciduous Trees .................................................... 46 Coniferous Trees.................................................... 62 Acknowledgements ................................................. 69 References & Further Reading .............................. 69 Photo and Image Credits ........................................ 71 i

How to Use this Guide This field guide contains general information about the basics of urban tree health, and maintenance. This guide is designed to be informative, yet easy to use for homeowners who may not be familiar with the technical aspects of tree care, pest and disease diagnosis, or tree identification. Pages are colour-coded to make it easier to locate each chapter. The colour-coding scheme is illustrated in the table of contents. Helpful tips and cautionary points are provided throughout this guide and are identified by the following symbols: Tree Tip: A hint, advice, special information, or point of interest relating to the topic. Indicates that special attention or caution should be applied. Many sources have been used to compile this guide; photo credits, references, and recommendations for further reading are also provided at the back of the book. We hope you enjoy using this handbook and that you find it useful for all your tree care needs!


Introduction Trees Winnipeg: Our Roots and How we’re Growing! Our Mission 

To protect, preserve and promote the urban forest and urban environment.

Trees Winnipeg (The Coalition to Save the Elms, Manitoba Inc.) is a non-profit charitable organization dedicated to the stewardship of the elm and other trees, forests and the urban environment. Although we are based in Winnipeg, we have members throughout Manitoba. The Coalition was originally formed in 1992 in response to government funding cutbacks to the Dutch elm disease (DED) management program and the perceived threat to the trees. Although DED was rampant in eastern Canada, it was not until 1975 that the disease was found in Winnipeg. Municipal and provincial officials sprang into action and initiated a cost-shared, integrated program of control which currently includes surveillance, sanitation, pruning, removal, therapeutic injections, basal treatments, education, community action, research, reforestation and preventative programs. In 1981, the Province of Manitoba enacted the Dutch Elm Disease Act (now the Forest Health Act) regulating the care and control of elm trees. Over the years, both the province and the city have spent substantial dollars in managing the losses of DED. In Winnipeg, over $2 million each year is spent on DED control. The loss of elms to DED has been kept to a level of less than 2% of the total inventory per year, a figure considered acceptable to maintain a large elm population.


Before and after photos of the effects of Dutch elm disease on a residential street in Winnipeg, Manitoba. (Photo: Mike Allen, Former City of Winnipeg Forester)


But in 1991, all three levels of government slashed funding to DED control programs, thereby threatening the survival of the elms. We had seen how the cities of Minneapolis and St. Paul cut funding to D.E.D. control, resulting in the loss of thousands of elms. We saw pictures from cities across North America, where street after street was denuded of trees. We did not want to see that happen here. Over the course of a weekend, eight women gathered together and hammered out a plan to lobby government, raise public awareness about the potential catastrophe to the quality of life in Winnipeg. We formed the Coalition to Save the Elms and gathered the support of over 20 neighbourhood associations and environmental groups. We also started a petition to have funding reinstated to the D.E.D. control program. We managed to persuade the government to put over $1 million back into the program. As a result, instead of an escalation of the disease, the incidence actually decreased over the proceeding years and government commitment has not wavered. Energized by our success, we were determined to become the watchdog of the urban forest. While elms are still beloved in Winnipeg, we have updated our strategy to stress the importance of all tree species and increased biodiversity in our urban forest. In 2009, we changed our operating name to Trees Winnipeg to reflect the change in our scope. Working in partnership with the City of Winnipeg, we continue to provide training to hundreds of volunteers through practical, hands-on workshops on tree care. We sell cankerworm control supplies, and offer free educational materials on tree health to homeowners. In addition to publications on tree care, we also publish a quarterly newsletter, the Urban Forester, which is free to the public. We also coordinate Arbor Day, a free day for families to interact with the arborist community and other environmental organisations. We partner with federal, provincial, and municipal government agencies to help


increase awareness of urban forest issues, and collaborate with the University of Manitoba and the University of Winnipeg on urban forest research initiatives. We believe that trees are an invaluable part of our communities. For this reason, we continue to fight for the protection of trees against construction damage and insensitive development. We are working to increase public awareness of historic and notable trees in our city through our “All Trees Tell a Story” program, and to have a public tree bylaw enacted to prevent the needless destruction of trees.

The Need for Tree Protection Winnipeg is home to the largest American elm population in any city in North America. Over 140,000 elms grow on city boulevards, in parks and open spaces, golf courses, cemeteries, private properties and riverbanks. Our elms make up just a portion of Winnipeg’s urban forest of an estimated 8 million trees. Tree-lined boulevards and mature trees on private properties are distinguishing features for many communities within the city of Winnipeg, with many trees pre-dating the houses built around them. Currently, there is no protection for trees on private property in Winnipeg, despite the progress in tree protection policies in other major Canadian cities. In addition to needless removal for new developments, urban trees face the new threat of invasive pests from overseas. Over the last few decades, increases in global trade and travel have introduced foreign insects to urban areas throughout Canada; pests to which our native trees have little or no resistance.

The Importance of Community Involvement Having managed Dutch elm disease for over 30 years, we know from experience that early-detection of invasive pests is the key to reducing the rate of spread of invasive species. Winnipeg’s success in preserving its urban forest thus far is largely due to the efforts of dedicated volunteers and concerned citizens.


But there is much work left to do! New invasive species continue to threaten our native trees, and trees are continuously removed unnecessarily for new developments on both public and private property. Winnipeg residents can help by creating awareness of these issues in our own neighbourhoods, and by letting our city officials know that tree protection initiatives are important to our communities.

Winnipeg Forest Watch Before Trees Winnipeg (formerly Coalition to Save the Elms) was founded in 1992, a group of organized citizens volunteered to keep watch for Dutch elm disease in their communities. These were “Elm Guard Groups”, and their efforts were key in the early detection of the disease, and in helping the City of Winnipeg facilitate a rapid-removal program. This collaboration is credited with the success of maintaining Winnipeg’s native elm population, and is the reason we still have many elms remaining on our streets. Dutch elm disease continues to threaten our urban forest, and new invaders are spreading across Canada. For this reason, Trees Winnipeg is resurrecting the Elm Guard program under a new name: The Winnipeg Forest Watch Program. The Winnipeg Forest Watch (WFW) is a city-wide network of homeowners who volunteer to keep an eye out for invasive species and trees showing symptoms of decline and disease. Volunteer WFW officers look specifically for symptoms associated with invasive pests such as Dutch elm disease, emerald ash borer, Asian longhorn beetle, and gypsy moth (Chapter 2). Surveys are approximately 1 km in length, and are completed two separate times each summer; during the last week of June, and the last week of August. Volunteers fill out a brief survey form for each symptomatic tree they encounter and send the form to Trees Winnipeg. Trees Winnipeg compiles all this data and uses it to locate regions that may be potential areas of concern. Trees Winnipeg will then provide updates to the City of Winnipeg on the locations of trees or areas of potential risk for invasive pests.


Training and tool kits are provided to WFW volunteers. Hand-on workshops are offered before surveys start in the summer. The tool kit includes survey forms, clipboard, tree and pest identification guides and other useful materials on invasive species and their associated symptoms. Homeowners, local businesses, students, school groups and residents’ associations are all welcome to join! Contact Trees Winnipeg for more information on how be a part of the Winnipeg Forest Watch in your area.

June Sun









August Sun





Winnipeg Forest Watch surveys are completed two times during the summer; during the last week of June and the last week of August.


Red Alert! Invasive Tree Pests Trees Winnipeg encourages all homeowners to be on the lookout for the following invasive pests that continue to threaten our urban trees:

Dutch Elm Disease What is it? Dutch elm disease (DED) is a vascular disease caused by a fungal infection inside the tree. The fungus is spread by the native and European elm bark beetles as they feed on new twigs and bore into the bark to lay their eggs. What it does: Blocks transport within the causing the tree to die.

water tree,

Symptoms: Sudden wilting, drooping leaves, yellowing, or browning of leaves on one or more main branches; premature leaf-drop in summer. Prevention & Treatment: Currently, there is no single treatment for DED. Regular pruning of dying branches by a certified arborist can reduce points of entry for the elm bark beetle. Professionallyapplied fungicide injections may help prevent the disease in healthy trees. Note: Sticky bands are not designed to prevent DED. DED is the most destructive disease of elms in North America. It has devastated elm populations around the world. DED was first identified in the Netherlands and northern France in 1919.


DED is caused by the fungus Ophiostoma ulmi which induces elm cells to produce a toxic substance blocking the water conducting cells of the tree. The cells lose their normal function, resulting in wilting leaves and ultimately, the death of the tree. The disease is spread by elm bark beetles (tiny black or brown beetles, only 3 mm long), which carry the disease spores on their bodies from infected trees to healthy elms on which they feed. The adult beetle breeds in recently dead or dying elm wood. Breeding takes place between the bark and the wood where the female constructs brood galleries (channels) in a Vshaped formation at right angles to the grain of the wood. Eggs laid along the brood galleries hatch and the larvae feed and spread, producing their own galleries. When fully developed, the larvae pupate and emerge as adults. If this breeding takes place in diseased wood, the new adult beetle may emerge with the very sticky DED spores attached. These spores can cause new infections if introduced into the water conducting tissues of healthy elm trees when the beetle feeds in the upper crown of the tree. The overwintering adults emerge in mid-April to mid-May and feed briefly before selecting brood material. This feeding stage is responsible for the majority of DED infections. The disease is fatal to both large and small trees. The time it takes to kill the tree varies, depending upon age and growing conditions. Although younger trees seem to be somewhat less vulnerable than older trees, when a younger vigorous tree becomes infected, it can die within a few weeks. Older, slower growing trees may live for a year or two but eventually succumb to the disease. To a lesser extent, DED may be spread by underground root grafts between trees up to 13 m (40 ft) apart. Occasionally, the elm is affected by other diseases such as Verticillium wilt and Dothiorella wilt, which can mimic the symptoms of DED. If this is suspected, it may be necessary to test the sample in the laboratory to determine which disease is responsible for the symptoms.


Emerald Ash Borer What is it? Emerald Ash Borer (EAB) is a highly destructive beetle from Asia that feeds exclusively on ash trees. What it does: The larvae carve extensive, S-shaped galleries beneath the bark, limiting the tree’s ability to transport nutrients. This eventually causes the tree to die.

Symptoms: D-shaped exit holes in trunk which are flattened on one side; tree dieback from the top-down; epicormic shoots (suckers) on the main trunk or near the ground. Heavy seed production or extreme woodpecker feeding may also be observed. Signs of EAB are not foolproof. Call an expert to confirm that EAB is present. Prevention & Treatment: Help prevent the spread of EAB by not moving ash firewood, nursery stock or logs. At the time of writing, no chemical treatments or insecticides were available.

Emerald ash Borer (EAB) arrived in North America from Asia and was first found in Detroit, Michigan and Windsor, Ontario in 2002. Since that time, it has spread through eastern North America; likely through the movement of ash products like firewood, nursery stock, and logs. EAB breeds


exclusively in ash trees. Given the substantial native and planted ash populations throughout Manitoba, this invasive pest is a huge threat to the ash forests in our province. The adult beetle has a shiny emerald or coppery greencoloured body. The torpedo-shaped body is about 3.5mm wide, and 8-15 mm long. Adults feed along the edges of the ash leaves, mate, and then the females lay eggs in bark crevices. Eggs are difficult to locate as they are so small (approx. 1 mm) and are hidden in the bark crevices or under bark scales. The larvae are up to 32 mm long when they are fully grown and have a creamy white body and brown head. The larvae feed beneath the bark during the summer months, creating S-shaped, serpentine galleries through the trunk. These extensive galleries cut off the flow of nutrients to the tree, and the tree eventually dies. The larvae over-winter under the bark and mature in early spring. The adult beetles then exit the trunk through Dshaped holes (3-4 mm wide) – these holes are unique to the group of beetles to which the EAB belongs. Signs of infestation may include signs of feeding on the edges of leaves, and dieback from the top of the canopy. Epicormic shoots (suckers) may be present along the trunk to indicate the tree is under stress. Trees that are under stress may also produce an unusually heavy seed crop. Bark deformities such as cracks or splits may also be observed, but these are not foolproof as these symptoms can also be related to temperature (i.e. frost cracks). External symptoms of EAB can be difficult to identify with certainty; therefore, it is recommended that an expert be called to confirm that EAB is present.


Asian Longhorn Beetle What is it? Asian longhorn beetle (ALHB) is a shiny black beetle with white spots and long antennae with black and white bands; feeds on a variety of hardwood tree species. What it does: The larvae hatch just under the bark and feed on the living tissue inside the tree, eventually causing the tree to die. Symptoms: Large exit holes (1 cm across) in the trunk; sawdust on branches or around tree base from larvae feeding inside. Prevention & Treatment: Help prevent the spread of ALHB by not moving hardwood firewood, nursery stock or logs. At the time of writing, no chemical treatments or insecticides were available. Asian longhorn beetle (ALHB) is native to several Asian countries. It was accidentally introduced to North America by way of wood shipping products such as wooden pallets, crates, and other wood packaging materials. It attacks a variety of North American tree species including maples, poplars, willows, birch, hackberry, mountain ash, and elm. ALHB is a relatively large beetle (2-3.5 cm long), and is shiny black with white dots on its back. It has long, segmented black and white (or black and grey) antennae that are longer than the body. Eggs are about the size of a grain of rice and are easy to see as the female beetle chews a round pit 1-1.5 cm in diameter


on the bark of the tree to lay the egg. These egg pits will also leak sap which can cause dark spots on the trunk of the infected tree. The cream-coloured, worm-like larvae are quite large; reaching up to 5 cm in length, and 1 cm wide. Larvae hatch and feed in the sappy, green inner bark, and eventually interfere with water and nutrient transport within the tree. Trees die from the top-down, and significant feeding galleries can compromise the trees structure. Adult beetles feed on the leaves and the bark of young branches, further weakening the host tree. Young adults emerge from the tree from May to July, and are active until October. Eggs are laid in either June-July or in September-October and spend the winter deep inside the tree trunk. The beetle has no known natural enemies in Canada, and insecticides have been ineffective (as the beetle larvae feed inside the tree), making this beetle difficult to eradicate once it has become established. ALHB is often confused with the native white-spotted sawyer beetle; which is smaller and feeds on conifers rather than hardwoods and does not pose a threat to native trees.

Asian longhorn beetle is often confused with the harmless white-spotted sawyer beetle (Photo: Pennsylvania Department of Conservation and Natural Resources).


Gypsy Moth What is it? Gypsy moth is an invasive moth from Europe and Asia; the caterpillars feed on many species of deciduous trees in North America. What it does: The larvae (caterpillar stage) can cause severe defoliation. Repeated defoliation can cause the death of the tree; large infestations can defoliate large areas of forest. Symptoms: Outbreaks can result in trees being completely stripped of leaves, and frass (fecal matter) from the caterpillars may be seen on the tree. Caterpillars can be identified by 2 distinct rows of blue and red dots along their back. Egg masses are up to 4 cm across; are usually slightly raised and are beige/yellow in colour. Prevention & Treatment: Help prevent the spread of gypsy moth by not moving firewood, nursery stock or logs. Check your yard regularly for egg masses which can be found on trees trunks, firewood piles, bird houses, patio furniture, BBQ’s, vehicles, camping equipment, and other items in your yard.

Gypsy moth was first introduced to Massachusetts in 1869, and has become established in eastern Canada. Small populations in Manitoba (including Winnipeg) have been observed. Gypsy moths feed on a wide variety of tree species including oak, poplar, elm, maples and birch, but will


also feed other deciduous trees, shrubs and coniferous trees. Repeated defoliation can kill the host tree; large infestations can defoliate large areas of forest. Defoliation also causes stress to the trees, making them more vulnerable to other pests and diseases. Gypsy moth females are white with brown narrow zig-zag markings. The male is brown with similar markings. The colouration of these moths makes them difficult to identify as they look similar to many other common moths in this region. Caterpillars are easier to identify as they have long, hair-like setae and have 2 distinct rows of blue and red dots along their backs. These markings can distinguish gypsy moth caterpillars from other common caterpillars such as forest tent caterpillar. Egg masses can also be relatively easy to identify. Egg masses are 1.5-4 cm long and can contain up to 1000 eggs. Masses are slightly mounded and are beige or yellow in colour. Females will lay egg masses on a variety of hiding places including tree trunks, the sides of houses, in woodpiles, under patio furniture and BBQ’s, outdoor toys, vehicles, camping equipment, trailers, boats and other items stored in your yard. Be sure to inspect your property in early spring. Eggs are laid in late summer and hatch the following spring; coinciding with leaf development. Caterpillars crawl up preferred host trees to begin feeding on the new leaves. They tend to feed at night, and crawl down to shady spots during the day. After about 8 weeks of feeding, mature caterpillars will seek a shady spot to pupate; adult moths emerge in late July and August to mate. Despite having wings, female moths are heavier than males and are unable to fly. Transporting firewood can destroy millions of trees! Beetles and larvae hiding in firewood can spread from your wood pile. Don’t move firewood from your cottage or campground; burn it on site.


Urban Forest Pests and Diseases The following pages contain basic information on some of the most common pests, diseases and environmental stresses that affect Winnipeg trees. Entries are organized under three headings according to the area of the tree that displays the most visual symptoms:   

Leaves and Canopy Fruits, Blossoms, & Twigs Main Trunk and Branches

Visual symptoms and suggestions for treatment are included for each entry, but additional information is available from your arborist or local tree nursery. Please also consult chapter 2: Red Alert! Invasive Tree Pests for information on symptoms associated with invasive species of interest. Always follow label directions and safety precautions when applying chemical treatments.

Leaves and Canopy Salt Damage Symptoms: Canopy dieback of trees along roads or boulevards; formation of “witch’s-broom” branches on deciduous trees and a “burned” look to evergreen leaves. Symptoms are most commonly observed on the lower branches. What it does: De-icing salt used on roads and sidewalks can affect trees by contaminating the soil or by spraying onto the canopy from passing vehicles. Salt toxicity in the


soil reduces the trees ability to take up water and nutrients; salt spray on the canopy desiccates twigs and foliage. Prevention & Treatment: Use de-icing salts sparingly and avoid piling salt-laden snow and ice near tree trunks or root systems. On high-traffic streets, sidewalks and boulevards, select salt-tolerant species for planting (i.e. elms, ash, cedars, etc.).

Flooding & Drought Symptoms: Standing water, leaf chlorosis, defoliation, reduced leaf size and shoot growth, heavy seed crops in the years following the flood, and crown dieback are all symptoms of flooding. Conversely, symptoms of drought include leaf wilting followed by premature browning and leaf-drop. Needles of pines and other conifers will turn brown. What it does: Flooding can damage and kill trees by limiting oxygen intake of their roots, restricting the ability of roots to draw up water. The after-effects of a flood can include the deposition of sediment on roots (which continues to restrict oxygen availability), changes in soil pH, or the removal of soil around roots, which reduces the structural stability of root systems. Tree species vary in their tolerance to flooding; and young or over-mature trees may be more susceptible than healthy, adult trees. On the other hand, water is required by trees for various physiological processes. In drought conditions, the tree can not complete these processes, and will die if water does not become available. Prevention & Treatment: Consult with your arborist about possible treatments or suitable trees for planting in floodprone areas. Watering trees can not only sustain them during dry spells, but can also help maintain general tree health and resistance to pests and diseases. For more on watering, please refer to page 42.


Nutrient Deficiency Symptoms: Leaf chlorosis, indicating a lack of chlorophyll in the leaves. What it does: In Manitoba, soil pH is often high, causing soil iron to be rather low. Prevention & Treatment: Iron chelate can be added to the soil to ameliorate this problem. Left untreated, nutrient deficiency will eventually cause the tree to die.

Winter Desiccation

Symptoms: The primary symptom of winter desiccation is reddish discoloration of evergreen foliage above the winter snow-line.

What it does: Winter desiccation occurs when the parts of the tree above the snow-line are exposed to warm dry air and sunlight when the ground is still frozen. The needles begin to transpire moisture, but roots are unable to replace this moisture and needles turn brown as a result. Damage is more common on exotic species or opengrown trees than native, sheltered trees. Trees generally recover, but if damage is extensive or occurs over several consecutive years, it can result in severe dieback or whole tree mortality. Prevention & Treatment: Buds are not generally affected and trees usually recover within a few years. A burlap covering can be effective in protecting trees from winter desiccation, provided the fabric is attached to wooden poles and does not come into contact with the foliage. Alternatively, rough up the snow around the south and


south-west sides of the tree throughout the winter. This reduces the sunlight being reflected on the tree.

Oak Decline Symptoms: Wilting of foliage from the top of the oak tree canopy downwards. Foliage eventually turns brown and remains on branches for about a year before falling off. Simultaneously, the two-lined chestnut borer often gains entry to the tree, causing branch dieback, and whole tree mortality within 3-4 years. What it does: Bur oak is highly sensitive to any changes in soil compaction, injury from construction equipment, or changes in the moisture content of the soil. Changes of this type often predispose oak to the two-lined chestnut borer, which tunnels through the phloem of the tree, restricting the flow of water and nutrients from the roots to the leaves. Prevention & Treatment: Watering and fertilizing trees with phosphorus fertilizers during dry periods can help maintain the general health of the tree. Pruning dead limbs that have been infested by the borer may also help prolong the life of the tree. Dead branches should be pruned in fall or winter at least 0.5 to 1.0 m away from the infested portion of the branch .The removal of trees that have been killed by the borer is also recommended to prevent the spread of the beetle. Any infested wood that has been removed should be buried, debarked, or chipped.


Cankerworms Symptoms: holes in leaves or complete canopy defoliation of deciduous trees in spring-early summer. Leaf veins and midribs are left intact. Long, silken threads and caterpillars (inchworms) may be observed in late June or early July. Spring cankerworms are mottled dark brown, while fall cankerworms come in two colour variations: light green and light brown with a dark green stripe on its back. Both species feed at the same time in spring. Small, brown-grey egg masses may be found in organized rows on the main stem or branches. What it does: Cankerworm caterpillars feed on the leaves of many deciduous trees in Winnipeg, including elms, Manitoba maple, basswood, apple, cherry, and occasionally oak and ash. Generally, trees recover by putting out a second flush of leaves in mid-July. Outbreaks occur in cycles, and high populations can cause severe defoliation of the entire canopy. Several consecutive years of severe defoliation may make the tree more susceptible to other pests, or cause the tree to die. Caterpillars hang down on silken threads once feeding is finished, and pupate in the soil. Silken threads and hanging caterpillars may become a public nuisance. Prevention & Treatment: Adult spring and fall cankerworm moths lay eggs in the spring and fall


respectively. Sticky bands may be an effective preventative measure when populations are expected to be high, and are a good tool for monitoring populations from year to year. Sticky bands capture the adult female moths (which are wingless, and must crawl) before they lay eggs in the canopy. Bands should be installed in September and removed at the end of May to be effective in capturing both species. Bacillus thuringiensis var. kurstaki (Btk) is an insecticide available at home-improvement stores and nurseries. It is derived from a soil bacterium and is highly effective against active caterpillars when properly applied. Btk must be applied while caterpillars are feeding, and may require an arborist for large area applications or tall trees. Btk is considered safe for residential use as it is only harmful to caterpillars and it degrades quickly in sunlight or rainy conditions. Tree Tip: How to Band Your Tree


Elm Spanworm Symptoms: The elm spanworm caterpillar can be identified by its looping crawl, dull or black body, and rust-coloured head. It initially creates a shot-hole effect in deciduous leaves, meaning damage can be observed as round holes in

leaves. Eventually, the larva will consume most of the leaf, leaving the major veins and midrib intact. Egg masses can be observed in July in irregular groupings on the undersides of branches or tree trunks. Adults possess wingspans of 30-37mm and are powdery white in colour, often congregating around lights at night in late June and July. What it does: The elm spanworm can cause the complete defoliation of shade trees during an outbreak. Despite its name, elm spanworm attacks many other tree species beside elms. Webs and frass in trees and shrubs can be unsightly. Prevention & Treatment: To control populations of elm spanworm, small twigs observed to contain egg masses should be pruned out, and larvae can be sprayed with Bacillus thuringiensis var. kurstaki (Btk) when they are actively feeding on foliage. Sticky bands are not effective against elm spanworm.


Forest Tent Caterpillar Symptoms: Grey-brown egg bands around twigs in late summer or spring. Larvae sun themselves in large groups on branches or on silken mats on the main trunk during the summer. Larvae can be identified by their broad, bluish lateral bands, narrow, broken orange lines and white keyhole shaped markings. What it does: Caterpillars feed mainly on trembling aspen, though it may feed on other species if its preferred tree is unavailable or already defoliated. Although the geographic extent of outbreaks can be very large, they seldom last longer than four years. Healthy trees can stand several consecutive years of defoliation, but they may suffer twig mortality, reduced radial stem growth, and smaller leaf sizes. Prevention & Treatment: If the masses of migrating larvae become a public nuisance, they can be sprayed with biological (Bacillus thuringiensis var. kurstaki -- Btk) or chemical insecticides. Consult with an arborist to arrange large-scale applications. Sticky bands are not effective against forest tent caterpillar.


Spruce Budworm Symptoms: A caterpillar that feeds on spruce trees. Silken webbing can be seen around newly formed buds in spring. Later in the spring, webbing becomes visible on branch tips and the accumulation of dead, partially consumed needles and buds gives the crown of the tree a rusty, scorched appearance. Larvae can be identified by their yellowish-brown bodies, rows of small white spots, and black heads. What it does: The caterpillars feed on the buds and needles of spruce trees. Spruce budworm goes through periodic outbreaks, during which whole-tree mortality can occur within 5-7 years of heavy feeding, particularly on over-mature trees. Prevention & Treatment: The biological insecticide Btk is often used for spruce budworm control. In order for it to be effective, the larvae must ingest the product quickly after its application. For this reason, Btk should be applied in the spring while larvae are out feeding on buds and new needles.

Spruce Bud Scales Symptoms: Heavy feeding by spruce bud scales causes discolouration and needle loss. Female scale insects on spruce are stationary, round, reddish-brown in colour, and approximately 3 mm in diameter. They


generally cluster in groups of 3-8 insects at the base of twigs, especially on lower branches. What it does: Needle loss and discolouration usually begins in the lower branches and spreads upwards through the tree. Crawlers hatch in June and excrete honeydew as they feed. This honeydew is then colonized by a black, sooty mould that can be observed on foliage and branches. Prevention & Treatment: At the time of writing, the insecticides registered for use on spruce bud scale included malathion, dimethoate, and diazinon. These products should be applied when crawlers are out feeding between late June and early August.

Spider Mite Symptoms: Mites are piercing-sucking foliage feeders that can be significantly damaging to ornamental or shelterbelt trees. They cause fine stippling on needles that increases in intensity, eventually giving needles a bleached appearance. Another characteristic symptom of spider mites is fine webbing around twigs and needles. What it does: Damage on larger trees is initially restricted to the lower branches, but eventually it may spread to the rest of the crown and can kill trees after several years of severe damage. Prevention & Treatment: Mites tend to thrive when trees are drought-stressed, so watering trees during dry periods can help to alleviate mite damage. Another option is to spray down trees twice a week during heavy feeding periods in the summer with a heavy flow of plain water from a hose.


Aphids Symptoms: Often the first sign of an aphid infestation is a sticky honeydew coating on everything underneath an infested tree. Other prominent symptoms include a mottled appearance on leaves and, in severe cases, premature leaf drop (also refer to Galls, page 31). What it does: Aphids cause damage by inserting their mouthparts into leaves and sucking out the fluids inside. Eggs overwinter and hatch into nymphs, which feed gregariously and develop into asexual females. Several successive generations of these females (either winged or wingless) are produced during a single growing season before females lay their eggs in the fall. Dispersal occurs when winged adults fly to new hosts or new parts of the host tree they originated on. Prevention & Treatment: Small populations may be sprayed off with a garden hose and water; larger populations may require an insecticidal soap. Check with your local garden centre for additional chemical treatments.

Leaf-Mining Insects Symptoms: The earliest symptom is brown blotches on deciduous leaves in June. As larvae continue to feed inside leaves through the summer, these blotches merge and leaves turn almost completely brown. Larvae are whitish, slightly flattened in appearance, and 6-7 mm long. What it does: Leaf miner larvae feed between the upper and lower surfaces of leaves. Although the leaf tissues of infested trees can be almost entirely destroyed by larvae,


vigorous tree can withstand many years of moderate damage. The insect may cause some branch and crown dieback if the tree is already stressed; this is particularly true of birch trees, which are sensitive to the combined effects of drought and leaf miners. Prevention & Treatment: Larvae are somewhat protected inside leaves; the insecticides required for effective treatment must be powerful synthetic chemicals designed to interfere with egg laying by adult female sawflies in mid to late May. Check with your arborist or local nursery for products that are currently available.

Anthracnose Symptoms: Tancoloured blotches on ash leaves and distortion of leaf shape. Initial symptoms in the spring include water-soaked spots on shoots and leaves. What it does: This disease may also result in defoliation of the tree and dieback in the crown if defoliation occurs for several consecutive years. Highly stressed trees may succumb to the disease and die. Anthracnose is caused by a fungus that can infect any succulent plant tissue. This fungus survives the winter in twigs, petioles, leaf veins, or seeds. Prevention & Treatment: Some methods homeowners can use to reduce the spread of the fungus are to remove fallen leaves in autumn (since the fungus overwinters in these leaves), and to prune trees to promote good air circulation and speed up the drying of foliage. Check with an arborist or your local nursery for chemical treatments that are currently available.


Bronze-Leaf Disease Symptoms: Yellowish-brown, orange, or reddish-brown areas form on leaves in mid-summer near their margins and spread inwards, often leaving major veins and the midrib of the leaf green. What it does: A fungus causes bronze leaf disease. In the first year of infection, affected leaves will generally be confined to a few branches and will remain on the tree during the winter. However, as the disease progresses, crown dieback can occur and wholetree mortality can result after only a few years. Fungal spores are believed to disperse with rain in April and May. Prevention & Treatment: Avoid planting some varieties of poplar (i.e. tower poplar and Swedish aspen) in areas where the disease is known to occur; these species are highly susceptible. At the time of writing, there were no registered chemical controls for bronze-leaf disease.

Fruits, Blossoms & Twigs Black knot Fungus Symptoms: Affects cherry trees and related species. Greenish brown to black swellings along branches; infections can be quite extensive. These “knots” are olive green colour in spring, turning black in the fall. What it does: Black knot is contracted when fungal spores infect young branches in the spring. The fungus initiates swelling of the branch vascular tissue. Swellings increase in


size each year and heavily infected trees often exhibit deformities and stunted growth. Infected branches will eventually die if untreated. Prevention & Treatment: To treat, branches with knots should be pruned and destroyed in the fall/winter, or before new growth begins in the spring. Cuts should be made six to eight inches below the lowest visible part of the knot, and pruning should occur on all nearby infected trees. A copper-based fungicide can be applied in the spring when the green tissue of the knot begins to form, and again just before flowering.

Fire blight Symptoms: The first symptom of fire blight is the blackened, water-soaked appearance of blossoms, which eventually turn brown or black as they wilt and die. Young twigs and leaves also blacken and wilt, and fruits often rot rapidly. Eventually, the disease can cause cankers to form on branches and trunks that appear scorched and water-soaked due to the oozing of bacterial masses. What it does: Fire blight is caused by a bacterial disease that spreads via wind, rain, insects, pruning equipment, or the transportation of fruits by humans. Blossoms and tender shoots of susceptible trees contract the bacteria in the spring, after which time the infection spreads to branches and stems. Prevention & Treatment: Branches should be pruned off 20 cm below cankers during the tree’s dormant period to


prevent the spread of bacteria the following spring. During the growing season, infected areas can be removed, but cuts should be made at least 30 cm below the visibly infected areas. Pruning tools should be disinfected between each cut. Streptomycin and copper compounds can be applied every three days during the tree’s blossoming period.

Ash Flower Gall Mite Symptoms: The ash flower gall mite attacks male ash flowers in the spring, which results in the formation of brown to blackish cankerous masses. What it does: The damage resulting from this mite is minimal, and trees do not suffer mortality or growth decline unless they are under additional stress. The blackened, abnormally-shaped galls can become unsightly along boulevards or on ornamental trees. Prevention & Treatment: One solution is to plant only female ash trees, as the mite will not attack female flowers. For trees that have already been established, dormant oils can be applied in late winter or early spring before the tree leafs out. Chemical insecticides can also be applied while blossoms are forming in spring. On a small scale, affected masses can be pruned out of the tree.

Scale Insects Symptoms: Scale insects can be found any time of year on the lower surfaces of leaves or on twigs of both deciduous and coniferous trees. They are very small, 2-5mm in length, may range in colour from mottled brown to grey or whitish, and are often oval or pear-shaped. The foliage on heavily


infested trees will appear pale or thin in comparison with healthy foliage. What it does: Scale insects are stationary feeders, meaning they attach themselves to plant tissue and suck out the sap. Large infestations may weaken or kill stems and branches, but whole tree mortality is rare. Prevention & Treatment: Dormant oil can be applied in the spring before the leaves emerge to limit the spread to other flowers on the tree. Dormant oil can also be used as a preventative measure on healthy trees to kill any overwintering insects.

Apple maggot Symptoms: Pin pricklike markings in the skin of apples where females have laid their eggs, giving the fruit a dimpled appearance. The adult apple maggots (fruit flies) can be identified in August by the white spots on their backs and the striking black bands on their wings. What it does: The larvae cause damage to the fruit through extensive tunnelling, but they are much more difficult to detect than adults. When larval tunnels become quite extensive, they cause discolouration inside of the fruit. Prevention & Treatment: Organophosphate insecticides are used to control apple maggot. Consult with your arborist or local nursery staff for recommendations on the products


that are currently available. Alternatively, Tree Tanglefoot® can be used to coat Styrofoam or tennis balls which are then hung from branches in the tree. This helps control the adult flies and may reduce the number of eggs laid.

Galls Symptoms: Galls are abnormal swellings on deciduous trees and can occur on leaves, petioles, twigs or buds and come in a variety of shapes and colours depending on the insect (aphid, sawfly, etc.) or mite behind their formation. On poplars, galls are usually light green and form when aphid nymphs begin feeding on developing shoots in the spring. Alternatively, the poplar bug gall mite causes cauliflowerlike galls to form on buds and fungal diseases can stimulate the formation of globe-like branch galls on poplar. On willow and oak leaves or twigs, galls are often caused by wasps or sawflies, and may be green or brown in colour. Finally, pale green, finger-like pocket galls can form on elm leaves with a mite infestation. What it does: Generally galls cause little damage to trees, but may reduce their aesthetic value, as infested trees can become unsightly or coated in honeydew (i.e. aphid infestation).

Main Trunk & Branches Frost cracks Symptoms: Straight, vertical splits on the main trunk. Note: Vertical splits or scars that twist around the entire length of the trunk may be caused by lightening). What it does: Frost cracking is initiated during the winter when a tree trunk is exposed to direct sunlight and warms up to 10oC above the ambient air temperature. When this heated area is suddenly shaded, the bark temperature drops rapidly, causing linear cracks to form. If this occurs repeatedly, the crack may extend deep into the annual rings of the tree and become a frost crack. Often, these cracks


widen in the winter during cold snaps and close during the spring and summer. Injury from frost cracking can be severe and may cause the tree to become susceptible to wind throw or provide entry for decay organisms. Prevention & Treatment: Consult with your arborist to determine if treatment or tree removal is necessary.

Stem Cankers Symptoms: Stem cankers, such as hypoxylon canker of poplar, are caused by fungal infections. Hypoxylon canker appears initially as a sunken, orange area on the main stem, and fruiting bodies of the fungus may also be visible as rough greyish areas on the stem. What it does: cankers often girdle the stem as it progresses, eventually causing the tree to die or even topple. Cankers such as this one are often secondary pathogens, meaning they appear on trees that have been predisposed to another stress prior to infection. Trees with hypoxylon canker can die within five years if the infection occurs on the lower main stem. Prevention & Treatment: Remove infected trees from the site as soon as possible to prevent the disease from spreading to other trees. Dispose of infected wood on site as the fungus can survive on dead material and be a source of infection for other trees.

Bacterial Wetwood (Slime Flux) Symptoms: Fresh infection appears as wet slime on the main trunk; usually originating from a wound such as a broken or pruned branch. Older infections appear as a yellow-brown discolouration on the trunk or a light-grey/white crust.


Slime that drips on to grass or vegetation beneath the infection may cause dead patches. What it does: Bacterial wetwood or slime flux is caused by various species of bacteria and occurs just under the bark. Bacteria enter the tree through pruning wounds, bark cracks or branch crotches and interact with the sugars in tree sap. This results in the creation of gas and pressure builds beneath the bark until it extrudes through cracks or wounds in the bark. The slime is toxic to the surrounding cambium and may prevent the wound from completely healing itself, though it does not appear to significantly affect tree structure or strength. Prevention & Treatment: Be careful when pruning to avoid wounding branches. Protect trees from root damage and soil compaction. Periods of drought may increase the occurrence of slime flux, so watering during drought conditions is recommended.

Animal damage Symptoms: The most common forms of damage on young urban trees include root clipping and debarking at the base of the trunk by voles, rabbits or squirrels. Mature trees may be debarked by porcupines, or deer slightly higher up on the trunk. Trees along river banks may be susceptible to cutting by beavers. The


yellow-bellied sapsucker, a small (20-23 cm) woodpecker with long white wing markings, can also cause damage by pecking rows of through the bark and into the sapwood of a tree. Note that sapsucker holes are typically arranged in orderly rows; holes that are randomly located on the trunk may be caused by wood-boring insects. What it does: The outright damage on young trees often causes morality, and damage to mature trees can create entry points for fungal pathogens. If light damage is sustained, trees usually make a full recovery, but branches can be girdled and permanently damaged under more severe attacks. Prevention & Treatment: Damage can be controlled by wrapping strips of burlap around damaged areas from April to late summer.

Trunk-Boring Insects Symptoms: Often the first sign of a borer infestation is varnish-like resin flowing out of wounds in the bark. Creamy white larvae approximately 40 mm in length can also be observed feeding inside the trunk when bark is peeled away, and boring dust or “frass” can be observed around the entrance and exit holes of the beetle. If a tree is heavily infested, tree mortality will occur from the topdown. An example of a common borer is the bronze birch borer, which can cause significant damage to birch trees and result in tree mortality. What it does: The larvae of trunk-boring insects hollow out the heartwood or tunnel beneath the bark of infested trees.


In heavy infestations, the core of an infested tree can become so severely weakened by larval feeding tunnels that it topples due to high winds. These borers often do the most damage to open-grown trees along boulevards or in parks. Borers that tunnel beneath the bark of the tree cut off the flow of nutrients and eventually cause the tree to die. Prevention & Treatment: Make trees less susceptible to boring insects by watering and/or fertilizing during dry periods. At the time of writing, there were no chemical treatments available for trunk-boring insects. The best management practice is to remove heavily infested trees so that they do not topple during a windstorm and damage property.


Basic Tree Care Tree Planting As well as preserving and caring for mature elms and other tree species, it is important to regenerate the urban forest. In cities and towns, the natural cycle is broken by human activity. In the concrete jungle, trees are prevented from reseeding that occurs in natural or rural forests. We must plant more trees to ensure a mix of ages and a green canopy in the years to come. It is vital that we increase species diversity by planting other varieties of trees that are suited to our climate. We must not over-plant one species of tree that can be wiped out by a single disease or insect infestation. Practical tips to consider when planting trees: 1. Tree Selection - Many factors should be taken into account when choosing a tree, including the mature size and shape and how it fits into your landscape plans. Growth rates, hardiness (ability to withstand weather extremes) and salt tolerance must be examined when selecting a tree or designing a landscape plan. 2. Site Selection - The conditions of the planting site are equally important. How much sunlight and moisture is available? What are the wind conditions? What type of soil is present? What is the location of the planting site in relation to other trees, buildings, intersections, fences, house foundations, overhead wires, etc.? Tree Tip: An arborist or the staff at your local nursery can advise you on the best trees to plant for your site.


3. Planting the Tree Successful planting starts with proper site preparation. Digging the hole for your new tree is the first step. The hole should be at least 30 to 60 cm (1 to 2 ft.) wider than the size of the root system. A large hole will allow better root growth especially in poor soil. Roughen up the side of the hole, which should be as wide at the bottom as at the top. Discard any rocks or debris.    

Use original soil from the planting hole as backfill. Break up clods of compacted soil to ensure small pore spaces and to avoid large air pockets. Poor soils can be amended with organic material or loamy top soil, although too much amendment can cause roots to be bound within the planting hole. A ratio of one-third amendment mixed with two-thirds existing soil will increase water holding capacity. Use this as a transition zone to the existing soil.

Dig the planting hole and backfill with enough soil to hold the tree just slightly higher than the depth at which it was grown in the nursery. Tamp the soil and place the tree in the center of the hole. Fill the hole three-quarters full, tamping to remove air pockets. If the tree is balled and burlapped, cut and remove all twine around the trunk and pull the burlap away from the trunk and top of the ball. Exposed burlap above the soil line acts as a wick and causes the evaporation of water from the root ball. If a wire basket contains the root ball, remove or bend to ensure all portions are also below the soil line. Water slowly to saturate the soil and remove air pockets. Finish filling the hole with soil, tamp and water again. Tree Tip: Most trees should not be planted later than the beginning of October as the roots will not have a chance to become established.


Staking Newly planted trees may be good candidates for staking, but this is not always necessary. A new tree with a dense crown of leaves and a proportionally under-developed root ball may be staked. To determine if a tree should be staked, grab


the trunk of the tree and move it back and forth, watching for shifting soil around the base of the tree. Shifting soil indicates that the root system has not yet established and the tree is unstable. In this case, a stake will provide temporary stability for the root system to establish, but should be removed in 1-2 seasons. Natural movement of the trunk (i.e. from wind) helps the tree grow stronger. Trees that have been staked too long will be weak and prone to breakage.

Soils and Mulching Soil is the single most important factor for good tree health. In a natural setting, soil is replenished each year through the process of decomposing organic matter on the surface layer of the soil. Leaf matter settles and the micro-organisms work vigorously to break down this “mulch” into viable soil for the trees. To help improve the soil, leave some of the litter on the soil. Maintain a layer (3-4”) of natural wood mulch over the bare soil by adding new mulch each spring if necessary.

Pruning Why do we prune?    

Remove broken, dying or diseased branches Encourage new growth and tree vigour To either increase or decrease fruit production Aesthetics and tree shaping Remember! Pruning of elms cannot take place between April 1st and July 31st. It is a contravention of the Forest Health Act to prune elms during this period.

After you have pruned your elm trees, you cannot keep the elm branches for firewood. It too, is a violation of the Forest


Health Act. All cut elm wood should be taken to a municipal landfill site immediately for proper disposal. If you decide to prune the trees yourself, here are some hints to remember:    

Prune all dead or dying branches on a regular basis to improve the tree’s health and avoid future problems. Prune to maintain the desired shape or size and to keep the tree attractive. Prune crossing or rubbing branches to avoid further damage. Prune to increase or reduce density of the tree. Generally trees should be thinned to produce a more open plant allowing light and air to penetrate to the interior. However, if denser growth is desired, heading back is required.

Whether you prune your trees yourself or have the work done by a contractor, it is essential that all pruning equipment be disinfected prior to and during pruning. Disinfection (with 50:50 water and methyl hydrate), prevents the careless spread of disease to healthy parts of the tree or to other trees. Thinning Thinning is the removal of whole branches where they attach to the next major branch or the trunk of the tree. This process is used to remove weak, aged, dead, diseased or undesirable branches. Position the cutting tool closest to the portion of wood that is to remain on the tree, a point just outside the branch bark ridge. Improper cuts that leave stubs not only look untidy but can result in die-back through which disease and insects can enter the tree. Cuts that are too close (inside the branch bark ridge) result in a surface area too large for proper healing and defeats the natural ability of the tree to contain disease, again leading to decay and insect infestation.


Heading Back Heading or cutting back of a stem or branch just before the bud, is a very common pruning practice. If done properly, it can be very helpful in eliminating several types of growth problems. Heading back is often done at transplanting time. Some deciduous trees can benefit from pruning when transplanted to compensate for roots lost during the process. Heading back during transplanting allows your tree to open up and develop strong, sturdy new growth. It also shapes trees. Use the “one-third formula” when heading back. Never remove more than one-third of a live branch. As well, avoid removing large branches which will take away more than one-third of the tree’s total growth. Large Limb Removal Removing heavy limbs, 7 cm (3 in.) in diameter or greater, requires certain precautions to avoid tearing bark from the


tree trunk. The first cut into the branch is made on the lower side, about 30 cm (12 in.) from the trunk. The next cut is made on the upper side of the branch, about 35 cm (14 in.) from the trunk. Finally, the remaining stub is cut close to the trunk at the branch collar. This allows for a clean cut which will heal properly.

Treating Wounds Ensuring a proper pruning job will speed the healing process of the tree. Trees have their own defence mechanisms and will heal the pruning wound on their own so long as the reproductive cells in the ridge and collar are not damaged. Trees are usually painted for aesthetic reasons, but painting will not speed the healing process as is commonly thought. Household paints and wood preservatives are toxic, and should not be used.

Watering Mature trees can be difficult to water because much of their feeder root system may be inaccessible when located under roads, sidewalks or other structures. They may not actually require much watering except in the most severe conditions. Trees which are well adapted for the prairies can withstand periods of drought. The elm in particular, is a hardy tree highly suited to extreme conditions. However, if signs of stress (such as leaf and twig wilting) become apparent, watering may be necessary. Infrequent, thorough soakings are more beneficial than frequent slight waterings. Water should be distributed evenly to as much of the root system as possible. The easiest method is to use a sprinkler system. Water in the early morning about once a week for the length of time necessary to provide 3 cm (1 in.) of water. Tree Tip: Measure the amount of water by placing empty tuna cans under the sprinkler and water until the cans are full.


Fertilizing Trees adapted for our region grow well in our native soils, so fertilization in not usually necessary. Fertilization is a temporary treatment that does not improve the quality of the soil for the long term. Trees that may be candidates for fertilization would be those planted in poor soils, or are under stress from soil disturbance or construction. In these cases, consider improving the soil by adding compost and organic matter to ensure the long term health of your tree. Some exotic and ornamental trees and shrubs are not adapted to our soil conditions. These species may require fertilizing and additional care. If you do choose to fertilize your tree, fertilizer can be applied every two to three years in early spring before growth begins. Fertilizer can be applied to the surface or placed in holes around the trees. Beware of burning the turf if fertilizer is surface-applied. Make sure to water well after surface fertilizing. Tree Tip: When purchasing a new tree, make sure the tree is well-suited to the planting site at home! An arborist or local nursery staff will be able to notify you if the tree will require regular fertilization or special care. Do not apply fertilizer after the end of June as this can promote new growth that may not harden off properly and may be damaged by subsequent winter weather.

Winter Protection Some trees and shrubs, particularly evergreens, are prone to desiccation in winter or early spring, and take on a rusty or burnt appearance. For more information on protecting evergreens, please see page 17.


How to Hire an Arborist Pruning and cutting of larger trees should be handled by professionals. Standards of practice and the level of experience among tree care companies may vary greatly. Property owners who are considering the use of professional tree service companies should have the following specified in any contract:       

all costs including disposal fees and taxes, etc. start and completion times number of staff present and their qualifications type of equipment and materials cleanup and proper disposal procedures guarantees for workmanship prices/availability of additional or related services

A minimum of three estimates from different companies is recommended. References or referrals are helpful indicators of competence. Consider visiting the arborist’s other job sites to see their workmanship. Ensure that the companies have adequate liability insurance and that staff with valid Manitoba Arborist Licenses or ISA certification (International Society of Arboriculture) will be present on the job at all times.


Tree Identification This section contains information on some of the most common urban trees in Winnipeg. Species are categorized as either deciduous or coniferous trees. Each species has unique characteristics that set it apart from other species; however, individual trees within a species may vary slightly in appearance due to pruning, disease, genetics, and site conditions. We have worked hard to highlight key features to look for when identifying each species. Photos, tree silhouettes and diagrams are also provided to help in identification. Note: Tree silhouettes from Natural Resources Canada. Other image sources provided on page 71.

Illustrated Terms

Simple leaf Single-toothed leaf

Double-toothed leaf


Compound leaf

Lobed leaf


Deciduous Trees American Elm

Ulmus americana L.

Tree Form: Deciduous tree, 20-25 m tall, “broccoli” or umbrella-shaped crown. Leaves: Oval leaf, double- toothed edge, uneven base where it attaches to stalk, dark green above and paler green on underside. Bark: Dark grey-brown with broad, deep, intersecting ridges Berries/Flowers/Seeds: Seed are samaras; flat, oval, and winged (about 1cm), deeply notched at tip. Similar Species: Siberian Elm (Ulmus pumila) is smaller (10-20m) with leaves about 2.5 cm long and 1.25 cm wide. U. pumila tends to produce an abundance of seeds and lack the graceful umbrella-like crown shape of U. americana. New elm cultivars that have shown some resistance to DED have been planted in Winnipeg; similar leaf and crown to U. americana but typically smaller in size. Notes: Native species. Common on urban boulevards and riparian areas. Suceptible to Dutch elm disease (DED).


Manitoba Maple (Boxelder) Acer negundo L.

Tree Form: Small deciduous tree to 12 m with widely spreading branches. Multi-stem branching habit is common. Leaves: Pinnately compound, 6-7 cm long with 3-5 leaflets, coarsely toothed, light green above, grey-green below, may resemble a classic maple leaf. Bark: Grey-brown and smooth on young trees. Deeply grooved and darker on older trees Berries/Flowers/Seeds: V-shaped samaras (winged seeds), wrinkled often with woolly hairs. Hang in clusters. Similar Species: May look similar to ash due to the compound leaves. Notes: Different from other maples with its compound ashlike leaves. Native tree to Manitoba; common in parks and along river banks.


Silver Maple

Acer saccharinum L. Tree From: A medium to large tree (up to about 12 m tall) with a rounded, spreading crown. Leaves: Light green leaves are 15 to 20 cm long, with 5 or 7 lobes. Sinuses between lobes are very deep compared to other maples, and can be a distinguishing characteristic. Silvery colour on underside. Bark: Smooth and gray when the tree is young; becomes dark reddish brown and breaks into strips that peel at either end and make the trunk look ‘shaggy’. Berries/Flowers/Seeds: Largest samara of the native maples, wings 5 cm long widely spreading, maturing in spring. Similar Species: The silver maple is very similar to the red maple – except that its leaves turn pale yellow or brown, not red, in the fall. Also similar to imported varieties from Asia, though the silver maple tree and its leaves tend to be larger. Notes: Fast-growing tree best for parks and open spaces. Wood is very soft and prone to breakage. Prefers rich, moist soils; shade tolerant.


Green Ash

Fraxinus pennsylvanica


var. subintegerrima Marsh.(Vahl)

Tree Form: Deciduous tree to 12m, cylindrical-shaped crown. Leaves: Pinnately Compound, 25-30cm long, 5-7 leaflets (typically 7), oval, slightly toothed or smooth, tapered at each end. Yellow autumn colour. Bark: Greyish-brown, becomes patterned bark on mature trees.




Berries/Flowers/Seeds: long and slender, single-winged, flattened samara 3-6 cm. with a slender, thin seed cavity. Similar Species: Black ash, Manitoba maple, manchurian ash. Notes: Very common tree planted on boulevards and in parks; found in natural stands along river banks. Moderately shade tolerant. Susceptible to emerald ash borer (EAB).


Black Ash

Fraxinus nigra Marsh. Tree Form: Slender deciduous tree with narrow, open canopy. Maximum height approximately 12 m. Coarse, ascending braches. Leaves: Pinnately compound 7–11 leaflets, 10-14 cm long. Leaflets elongated, oval, and stalkless. Tapered to a long, slender tip. Hairless except for dense tufts of hairs where leaflets attach to leaf stalk. Bark: Soft, with corky ridges which are easily rubbed off by hand. Berries/Flowers/Seeds: Slender samara, 2.5-4 cm long, wing broad, often twisted and sometimes slightly notched at the tip. Similar Species: Green ash, butternut, black walnut. Notes: Found in natural stands and swampy woodlands in eastern Manitoba. Can tolerate standing water for several weeks, but not very shadetolerant. Easily confused with green ash (F. pennsylvanica), but can be identified by the characteristic gap between the terminal (end) bud and the first set of leaves and auxiliary buds (photo above).


Mancana Ash

Fraxinus mandschurica ‘Mancana’ Tree Form: Medium to large deciduous tree growing between 9 and 12 meters tall. Canopy is dense and oval to round in shape. Leaves: Leaves similar to black ash, compound, bearing 9-11 leaflets on a leaf stem. Green through the summer; they turn yellow in fall. Bark: Gray and smooth when young, fissures form with age.

Berries/Flowers/Seeds: Flowers are greenish-yellow. The fruit is dry, winged, and tan in colour. Similar Species: Black ash, green ash, mountain ash. Notes: Common landscape tree in suburban developments and parks.


Mountain Ash Sorbus sp.

Tree Form: Large shrub or small tree to 15 m in height, sometimes multi-stemmed. Short, rounded crown in opengrown conditions. Leaves: Compound leaves, 11-15 paired leaflets per leaf. Leaflets are 5-8 cm long, lance-shaped, thin and tapered to a point. Lower surface is hairless and lighter green than the top surface. Bark: Grey-brown, thin, smooth, forming loose papery scales on older stems or trunks. Berries/Flowers/Seeds: Flat clusters of small white flowers in summer. Clusters of scarlet red berries occur in August, 810 mm in diameter. Similar Species: There are two species of mountain ash in this region; showy mountain ash (S. decora), and American mountain ash (S. Americana). The latter is uncommon, and has slightly narrower, more sharply toothed leaves than S. decora. Notes: Can grow on a variety of sites including dry hillsides, rocky soils, and along swamp boarders. Berries attract birds and mammals.


Bur Oak

Quercus macrocarpa Michx.

Tree Form: Deciduous slow-growing tree up to 15 m tall, can live up to 200 years. Trunk is straight and distinct up to the top of the crown. Lower branches tend to grow nearly horizontal; crooked, gnarly in appearance.

Shiny brown

Leaves: 15-30 cm long, variable in shape with characteristic lobes. Underside of leaf is hairy. Green in summer; turn brown and leathery in fall.

rough, becoming deeply furrowed with ridges broken into irregular thick scales. Bark: Dark grey,

Berries/Flowers/Seeds: Acorns usually solitary; stalkless or short-stalked. Large cup encloses one-half or more of the acorn. Notes: Grows well in deep, rich soils and grasslands. Preferred food species for gypsy moth and two-lined chestnut borer.


American Basswood Tilia americana L.

Tree Form: Tall, straight tree, up to 35 m. Canopy symmetrical and rounded, spade or cone-shaped. Leaves: broad, toothed, heart-shaped leaves, 12-15 cm. Shade leaves can larger. Defined leaf tip. Underside pale green. Bark: Thin, smooth and light green-brown when young; mature bark is dark grey-brown and develops long, narrow, flat-topped ridges transversely divided into short blocks. Berries/Flowers/Seeds: Fragrant, creamy-yellow flowers appear in July. Seeds may be abundant; round, 8-12 mm wide with fine brown hairs. Similar Species: Catalpa (rare ornamental). Notes: Very shade tolerant, a good shade tree for yards, parks and boulevards.


White Birch (Paper Birch) Betula papyrifera Marsh.

Tree Form: Mid-sized deciduous tree, up to 20 m. Noted for its distinctive peeling white bark on the trunk. The branches are ascending and the younger twigs are brown in colour. The canopy is narrow and oval in shape. May occur as a single-stem or multi-stem tree. Leaves: Double toothed leaves are 5-10 cm in length and triangular in shape. The tips are pointed. The upper surface of the leaf is usually dull green; the underside is lighter green. Bark: When young, it is reddish-brown. The distinctive peeling white bark comes with maturity. It is thin and smooth. Berries/Flowers/Seeds: Catkins (1-3 cm in length) develop April to May. The fruit is dry and resembles a drooping cone. Notes: Grows in a variety of soil types but is not shade tolerant. It is susceptible to bronze birch borer. Do not peel the bark as it can harm the tree.


Balsam Poplar (Black Poplar) Populus balsamifera L.

Tree Form: Medium, deciduous tree that grows up to 25 m in height. The trunk is straight and the canopy is narrow. The branches are somewhat thick. Root system is wide spreading. Leaves: Fine-toothed edge with inward pointing teeth. 7-12 cm in length, leaves are dark green above and silvery green underneath. Warty glands may be present at the base. Bark: Smooth and greenishbrown when young. Matures to grey with furrowed thick ridges. Berries/Flowers/Seeds: Flowers emerge before the leaves in long catkins (7-10 cm in length). Capsules mature in the catkins and split in two when mature to release the seed. Similar Species: cottonwood.


Notes: Native tree, common on moist soils.



Trembling Aspen (White Poplar) Populus tremuloides Michx.

Tree Form: Tall deciduous tree up to 25 m in height. Trunk is long and slender with a rounded canopy. The root system is shallow and wide spreading. Leaves: 3-7 cm in length, oval ending in a short, sharp tip. The lower surface is paler than the upper surface. Leaves are hairless and fine toothed. Stalk is longer than the leaf and flattened. Bark: Smooth becoming furrowed with age and occasionally has diamondshapes. Young trees are light green to white in colour but darken with age. Berries/Flowers/Seeds: Catkins emerge before leaves. Capsules in the female catkin are conical and hairless and split into two when mature. Similar Species: cottonwood.



Notes: Can be found growing in dense forests in naturalized areas.



Populus deltoids Bartr. Ex Marsh. Tree Form: Large deciduous tree; mature height up to 30 m. Trunk can divide near the ground in open areas but is long and straight in closed forests. Canopy is conical. Shallow, widespreading roots. Leaves: Rounded teeth on each side except near the tip. Triangular and 5-10 mm in length. Upper leaf surface is bright shiny green. Bark: Young bark is smooth and yellowgreen. Mature bark is deeply furrowed and turns to dark grey. Berries/Flowers/Seeds: Catkins are 57 cm long. Similar Species: trembling aspen.



Notes: Native tree, common on moist soils; large specimens can be found along river banks.


Schubert Chokecherry

Prunus virginiana “Schubert” Tree Form: Up to 25 m in height. Pyramidal canopy with single trunk and suckers at the base or multistem shrub. Leaves: Elliptical shaped, new leaves are green when they appear but age to purple-red throughout the summer. Bark: Smooth and grey-brown. Berries/Flowers/Seeds: Small, white flowers clustered on a stem 2-3 cm long in spring. Flowers are followed by dark red/purple fruit in August. Notes: Drought and shade tolerant. Frequently produces suckers (shoots) at the tree base. Common in urban plantings and along boulevards; very susceptible to black knot fungus.


Amur Cherry

Prunus maackii Rupr. Tree Form: Small to medium size tree up to 8 m. Leaves: Same elliptic shape as the Schubert chokecherry; green and finely toothed. Glandular dots on the underside. Veins are prominent. Bark: Noted for its unusual copper colour and “papery” bark. Berries/Flowers/Seeds: White flowers, similar to those of the Schubert Chokecherry, in spring. Fruit are black and ripen in August. Notes: Can grow in full sun to part-shade. Attractive ornamental but it is sensitive to many diseases and insects.


Crabapple Malus spp.

Tree Form: Height and form vary depending on the species of apple (4.5 m to 9 m) Leaves: Oval-shaped and toothed. Trees bearing edible fruit have green foliage. Ornamental varieties of crabapple exhibit different leaf colours and may be green, greenish-red, red, or purple. Bark: scaly and reddish-brown. Berries/Flowers/Seeds: Trees may bear white, pink, or red flowers depending on the species. Fruit may be large and edible (up to 8 cm diameter) or small (2 cm) and good for birds (ornamental crab apples).


Coniferous Trees Jack Pine

Pinus banksiana Lamb. Tree Form: Up to 20 m in height or more. Branches are ascending and the crown is conical. Roots are wide spread and deep, usually with a tap root. Leaves: Evergreen needles in bundles of two (2-4 cm long). Pointed with a sheath at the base. Bark: Thin, flaky, and furrowed. Brown to reddish-brown. Berries/Flowers/Seeds: Seed cones can be straight but often curve inward. Cluster in 2’s or 3’s. Open only during extreme heat such as a forest fire. Similar Species: Eastern white pine (needles 5-15 cm long, in clusters of 5), red pine. Notes: Tolerates drier conditions and grows best in sandy soils. Not commonly planted on boulevards, but can be found in private yards and parks.


Red Pine

Pinus resinosa Ait. Tree Form: Large evergreen up to 25 m. Crown is conical, upper branches curving upward while lower branches are horizontal or drooping. Leaves: Evergreen needles in bundles of 2, 10-16 cm long. Tree canopy may look “feathery” from a distance. Bark: Broad, flat, scaly plates, reddish colour. Berries/Flowers/Seeds: Oval-shaped cones with almost no stalk. Cones open in the fall and are shed the following year. Similar Species: Jack pine, eastern white pine. Notes: Prefers sandy, well drained to dry soils. Tolerates shady conditions.


Black Spruce

Picea mariana (Mill.) B.S.P.

Tree Form: Tall evergreen can reach 20-30 m. Narrow, dense crown with many cones. Short branches, drooping lower branches. Dense “club” of branches may be observed on the top of some specimens. Leaves: Straight, blunt, green needles arranged individually on the stem (not in groups like on pines). White dots on the lower surface. Twigs slightly hairy on close inspection. Bark: Young bark appears shredded, reddish brown in colour; separates into darker, larger scales with age. Newly exposed bark olive or yellow-green. Berries/Flowers/Seeds: Cones are red to purple and oval in shape. Can be produced nearly every year and remain on tree up to 30 years. Similar Species: White spruce. Notes: Slow growing tree common in wet areas and bogs. May also be seen in parks and naturalized areas.


White Spruce

Picea glauca (Moench) Voss Tree Form: Evergreen, 25 m tall at maturity. Conical crown with horizontal branching. Leaves: Green needles are straight. Tips are pointed but not sharp. Unlike the black spruce, the white dots are on all sides of the needle and twigs are not hairy. Bark: Grey; smooth when young, turns scaly with age. Newly exposed bark salmon pink in colour. Berries/Flowers/Seeds: Cones are slender and cylindrical with blunt ends. Light brown. Similar Species: Black spruce, Colorado blue spruce. Notes: Shade tolerant and grows in a range of soil conditions. Common in yards, parks, natural areas and shelterbelts. Provincial tree of Manitoba.


Colorado Blue Spruce Picea pungens Engelm.

Tree Form: Dense, pyramidal evergreen up to 25 m tall. Branches are horizontal but lower ones may droop. Leaves: Needles attached individually to the branch. Colour varies; may be green, blue-green, or silvery-blue. Needles stiff and noticeably sharp when held in your hand. Bark: Scaly and brown. Berries/Flowers/Seeds: Cones are tan and approximately 10 cm long. Similar Species: White spruce. Notes: Often used in private yards and parks as an ornamental tree or as part of windbreaks.


Eastern White Cedar Thuja occidentalis L.

Tree Form: Dense, conical crown. Typical height at maturity is 15 m. Branches bend slightly downward, but gradually turn upward at tips. Leaves: Flat, scale-like leaves, 1-2 mm long. Bark: Thin and shiny reddish brown when young; turns to grey and forms thin, narrow strips with age. Berries/Flowers/Seeds: Seed cones oval, covered in thick leathery scales. 7-12 mm long. Notes: Ornamental varieties very common in yards and parks; often pruned into tight shapes and hedges.


Tamarack (Larch)

Larix laricina (Du Roi) K. Koch Tree Form: Conifer growing up to 25 m. Trunk is straight and the crown is narrow and conical. Leaves: Needle like, 2-5 cm long, in clusters of 12-20. Green in summer; needles turn yellow in autumn before falling off. Bark: Thin, smooth bark becomes scaly with age. Grey to reddish-brown. Berries/Flowers/Seeds: Seed cones are ovoid, 1-2 cm long. Open in mid-August and then shed. Notes: The only conifer to drop its needles for the winter. Yellow fall colour is vibrant. Grows well on moist soils.


Acknowledgements This handbook was prepared by Trees Winnipeg (Coalition to Save the Elms, Manitoba Inc.) with invaluable assistance from Environment Canada, the City of Winnipeg, and local tree-care professionals. Special thanks to University of Winnipeg students Evelyn Cruz Gochez, Katherine Dearborn, Carla Church, Stephen Kurz, and Carolyn Talbot for their help in gathering information and images for this handbook. Editor: Kerienne La France Reviewers: Mike Allen, Keith Knowles, Linda Morin, and Carolyn Talbot. References & Further Reading Printed Publications Coaltion to Save the Elms, Manitoba, Inc. 1997. Manitoba Elm Survival Guide. Winnipeg, MB. 48 pp. De Groot, P. et al. 2006. A Visual Guide to Detecting Emerald Ash Borer Damage. Natural Resources Canada, Canadian Forest Service, Ottawa, ON. 16 pp. Farrar, J. L. 1995. Trees in Canada. Fitzhenry & Whiteside Ltd. and Natural Resources Canada, Canadian Forest Service, Ottawa, ON. 502 pp. Hiratsuka, Y., Langor, D.W., and Crane, P.E. 1995. A Field Guide to Forest Insects and Diseases of the Prairie Provinces; Special Report 3. Natural Resources Canada, Canadian Forest Service, Northwest Region, Northern Forestry Centre, Edmonton, AB. 297 pp. Online Resources Canadian Food Inspection Agency. http://www.inspection.


Canadian Forest Service. Trees Winnipeg. City of Winnipeg, Insect Control Branch. http://winnipeg. ca/publicworks/bugline/ City of Winnipeg, Urban Forestry Branch. http://winnipeg. ca/publicworks/Forestry/forestry.asp Forestry Images. International Society of Arboriculture. Manitoba Hydro; Right Tree, Right Place. right_tree/index.shtml Natural Resources Canada, Canadian Forest Service (Tree Identification). Province of Manitoba, Conservation and Water Stewardship; Forestry Branch. conservation/forestry/ United States Forest Service.


Photo and Image Credits Page #


Image Before/after DED


DED infested tree

Source Manitoba Elm Survival Guide, Coalition to Save the Elms, 1997. Steven Katovich, USDA Forest Service, Minnesota Department of Natural Resources Archive, Cornell University Cooperative Extension Wyoming County; Agriculture Program; http://counties.cce. agriculture/programs/ipd/ emerald-ash-borer.htm Scott Guiser, Penn State College of Agricultural Sciences. http://buckshort.blogspot. ca/2012/03/yes-kissyour-ash-goodbye.html Daniel Herms, The Ohio State University, Donald Duerr, USDA Forest Service, USDA Animal and Plant Health Inspection Service, pot-it/ University of Wisconsin Extension, Cooperative Extension: Gypsy moth in Wisconsin, /gypsymothinwisconsin/

DED flagging 9

EAB adult beetle

Larval galleries

Exit holes 11

ALB adult beetle Exit holes


Gypsy moth adult female


Page # 13 15


Image Caterpillar


Salt damage

Cornell University Cooperative Extension Wyoming County; Agriculture Program;

John H. Ghent, USDA Forest Service,

Nutrient deficiency Winter desiccation

Mike Allen, Viburnum Tree Experts


Oak decline


Spring cankerworm Fall cankerworm Egg mass

Tree band 20

How to Band your Tree


Elm spanworm caterpillar Adult moth

http://counties.cce.cornell.e du/wyoming/agriculture /programs/ipd/salt_damage _trees.htm Jason Sharman, Vitalitree, Joseph O'Brien, USDA Forest Service,

Natural Resources Canada.

http://tidcf.nrcan.gc. ca/insects/factsheet/8955 and https://tidcf.nrcan. 0137

Mike Allen, Viburnum Tree Experts Manitoba Elm Survival Guide, Coalition to Save the Elms, 1997.

Heidi Fry,

Mark Dreiling, Retired, 22 Forest tent caterpillar Herbert A. 'Joe' Pase III, Texas Forest Service,


Page # 23

Image Spruce budworm frass


Caterpillar Spruce bud scales 25

Leaf-mining insects




Bronze leaf disease

Black knot fungus 28

Fire blight


Ash flower gall mite


Apple maggot egglaying sites Adult fly


Stem canker


Joseph O'Brien, USDA Forest Service, USDA Forest Service – North Eastern Area Archive, Steven Katovich, USDA Forest Service, Lance S. Risley, William Paterson University, Joseph O'Brien, USDA Forest Service, USDA Forest Service North Central Research Station Archive, Minnesota Department of Natural Resources Archive, John Hartman, University of Kentucky, Whitney Cranshaw, Colorado State University, Whitney Cranshaw, Colorado State University, Joseph Berger, USDA Forest Service North Central Research Station Archive,

Page # 33

Image Bacterial wetwood (slime flux)


Sapsucker damage


38 41

Rabbit damage How to plant a tree more than two metres tall Thinning


Illustrated terms: leaf descriptions


American Elm


Manitoba Maple

48 49

Silver Maple Green Ash


Black Ash leaves

Manitoba Elm Survival Guide, Coalition to Save the Elms, 1997. Manitoba Elm Survival Guide, Coalition to Save the Elms, 1997. Natural Resources Canada. me

Bill Cook, Michigan State University, Paul Wray, Iowa State University, unavailable Robert Vidéki, Doronicum Kft., Keith Kanoti, Maine Forest Service, Rob Routledge, Sault College,

Buds 51

Mike Schomaker, Colorado State Forest Service, Janet McLeod Scott 2008. Clemson University Cooperative Extension, Home and Garden Information Centre: http://www. c/tyk/2008/tyk01.html Steven Katovich, USDA Forest Service,

Manacan Ash tree

Kerienne La France, Trees Winnipeg Kerienne La France, Trees Winnipeg



Page # 52

Image Mountain Ash



Bur Oak


American Basswood


White Birch


Balsam Poplar leaves and bark


Trembling Aspen tree Leaves and trunk

http://www.ontariowildflo Richard Webb, Selfemployed horticulturist,

http://www.meridian.k12.i dent_work/kallenbach_tree s/American%20Basswood.h tml Richard Webb, Selfemployed horticulturalist, Natural Resources Canada. es/factsheet/53 J.S Peterson, USDA-NRCS PLANTS database

USDA-NRCS PLANTS Database / Herman, D.E., et al. 1996. North Dakota tree handbook. USDA NRCS ND State Soil Conservation Committee; NDSU Extension and Western Area Power Administration, Bismarck.


Cottonwood trunk


Schubert Chokecherry tree and leaves

75 es/factsheet/54 Kerienne La France, Trees Winnipeg

Page # 60

61 62

Image Amur Cherry tree and bark


Crabapple tree and leaves/fruit Jack Pine tree

Kerienne La France, Trees Winnipeg Kerienne La France, Trees Winnipeg R.A. Howard@USDA-NRCS PLANTS Database

Cones/needles 63

Red Pine tree

Joseph O'Brien, USDA Forest Service,

Needles/cones 64

Black Spruce tree


White Spruce


Colorado Blue Spruce


Eastern White Cedar tree, leaves and pruned shrub Tamarack tree (autumn colour)


USDA-NRCS PLANTS Database / Herman, D.E., et al. 1996. North Dakota tree handbook. USDA NRCS ND State Soil Conservation Committee NDSU Extension and Western Area Power Administration, Bismarck..



Natural Resources Canada, es/factsheet/49 Natural Resources Canada, es/factsheet/39 Kerienne La France, Trees Winnipeg Kerienne La France, Trees Winnipeg Kerienne La France, Trees Winnipeg Steven Katovich, USDA Forest Service, Natural Resources Canada, es/ factsheet/34



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