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Vol. 9, No. 2


A Prairie Trilogy:

The Urban Forests of Morris, Minnesota

By Gary Johnson


uick, what comes to mind when someone mentions Morris, Minnesota? Prairie landscapes and pheasants? Wind, wide-open sightlines? Just one more exit off an unending highway? Corn?

Now, why didn’t trees come to mind? Why not roses and hundreds of varieties of flowering annuals? Why not a top-flight university tucked into a historic campus of majestic elms and century-plus cottonwoods? Or why not almost 400 acres of city parks and tree-lined boulevards surrounding the university? A visit to Morris could change that perspective.

The Minnesota River Prairie. Crossing the landscape westward from the Twin Cities, passing through Glenwood and Starbuck, Morris suddenly appears as a small, rural community tucked between the moraines to the east and the Prairie Coteau to the west. From the beginning - around 1870 - Morris has been a farm service center, but there’s a lot of depth to the topography and the green canopy cover that greets you. Entering the community, a pretty steep bluff to the east hosts a solitary, modern windmill (turbine) that grinds out enough electricity to provide up to 60% of the electrical needs of the University’s campus. The wind turbine is only one of the many “green campus initiatives” that the University of Minnesota, Morris campus is noted for. The Pomme de Terre river stretches up from the Minnesota river and broadens to Pomme de Terre Lake more than 30 miles north of Morris. Along with the prairie, the river has long been the prominent natural feature of the area, winding almost due north/south through the prairie and farms and hosting the characteristic riparian species for western Minnesota: ash, elms, willows and cottonwoods. It’s not hard to understand why these tree species often dominate the communities that dot the western landscape…they’re the trees that survive and thrive.

A Prairie Trilogy continued on p. 4

Photo by Sue Granger

Inside This Issue 2 Perspectives Column 3 Mystery Tree 7 Urban Tree Planting 11 Systematics 13 Clip & Save: Tree Care Professionals 14 Monthly Forum Schedule 15 MnStac & Calendar 16 Preparing Your Community...

Visit MnSTAC on the Web at

The Minnesota Shade Tree Advisory Committee’s mission is to advance Minnesota’s commitment to the health, care and future of all community forests. ADVOCATE • Spring 2007


The Language of Trees

or … “Don’t just stand there … tell me who you are.”

By Lorrie Stromme


learned a new language about 10 years

ago: the language of trees. In college, I majored in English and French, and along the way I studied Latin, AngloSaxon, and Middle English. I didn’t realize that trees had a language, but once I found out, I was hooked. I’m not quite fluent, but getting there. Though mute, trees communicate. They have “tells” and identify themselves: the diamond patterns on the bark of green ash; the ruby flowers on red maples each spring; the zigzag branches on honeylocusts; the stalk-of-broccoli form of American elms; the twisted needles on Scots pine; the cones that point up (instead of down) on firs; and the giant, leathery pea pods on female Kentucky coffee trees (heck, this tree even reveals its sex!). We can often tell when trees are sick, thirsty, or salt-stressed. For example, we all know that a flagging branch and brown streaking in the sapwood of an American elm are symptoms of Dutch elm disease. Sometimes trees are just messing with your head. Spindle galls on maple leaves, the white streaks on elm bark, and ash flower galls look unsightly, but usually don’t affect a tree’s health. When I first started to learn the language of trees, I tried to teach myself by using plant keys, guidebooks (preferably with lots of pictures), walking up to a tree, and trying to etch its bark pattern into my brain. Nothing “took” for more than a week or two. Then, I took a three-month immersion course on the language of trees. My outdoor classroom was the Minnesota

Landscape Arboretum, and my teacher was Mike Zins, then an assistant professor of horticulture at the University of Minnesota (and one of the three best teachers I’ve ever had). My classmates and I followed Mike up and down hills at the Arboretum two days each week, after work, clipboards in hand. We used all of our senses to learn about woody plants. Yes, we even tasted them! Mike’s hilarious turns of phrase and dead-on descriptions helped me to distinguish one tree from another with ease. By the end of Mike’s class, I could identify over 200 trees and shrubs, with leaves and without, by both their common and botanical names. Probably everyone reading this article knows how to identify plenty of tree species. But for those who may want a refresher or a broader tree vocabulary, I recommend taking a course that provides hands-on experience. The University of Minnesota offers semesterlong courses on identification of woody plants and herbaceous plants. In addition, Dave Hanson in Forest Resources at the University of Minnesota teaches Tree ID to Tree Care Advisors and interested attendees at the Minnesota Shade Tree Short Course each year. Even as a dedicated tree-care professional, you may find a gap in your knowledge. When that happens, take a closer look at trees and “listen” to what they’re saying to you. Lorrie Stromme is a past president of the Minnesota Shade Tree Advisory Committee, a Master Gardener, a Tree Care Advisor, and a huge fan of life-time learning.

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Mystery Tree... There are several maples native to Minnesota and all of them have distinct leaves, samara and even bark characteristics. One of the maples has compound leaves which definitely separates it from the group. But, compound leaves are not the focus of this mystery. A hard maple that has taxonomists raising questions is the focus. The questions raised ask whether or not this maple should be classed as a separate species or placed as a sub-species of another? This particular maple has some unique characteristics like stipules on the petiole or leafstalk of the leaf. Beyond that, the lateral lobes (usually 3 strong lobes, rarely 5 lobes) of the leaf droop from the mid-vein. No other maple in Minnesota has these traits. Not only are the drooping leaves and stipules unique, but the leafstalks and the underside of the leaves are often described as hairy. Unfortunately, this maple is not utilized very often in the urban environment even though it is described as more drought tolerant than its closest relative. So, track down your best tree book and read up on the maple family. Solve this little mystery and see if you can’t find a place in the landscape for this very deserving maple…

Drooping lateral lobes Notice how the leaf stands off of the pavement…

Stipules at the base of the petiole…


Photos by Dave Hanson


Answer on page 14 ADVOCATE • Spring 2007

A Prairie Trilogy from p. 1 Town, Gown, Research and Gardens… They’re all lush and green. It would be easy for a community of this size, with this much diversity to be a bit fractured… but it isn’t. One part of the landscape blends into and compliments the next. The managers of the campus landscape respect and work with the city council and the city’s tree inspector, and they are all proud of the variety of plant materials featured in the horticulture display gardens at the West Central Research and Outreach Center. Yet even as they work in concert, this story really is a trilogy…three stories united by a central theme. The Town. This is a community of almost five and a half thousand residents (including university students). Teeming with trees, volunteers and civic pride, Morris has an urban forestry program that most communities could only hope to attain: over 5,500 public trees, an aggressive Dutch elm disease control program, and a unique, annual tree planting commitment. Although prairies do surround the area, this is an urban forest in the truest sense.

Photo by Sue Granger

The 5,500+ trees in Morris’ parks and boulevards are managed by two people in particular. Jim Dittbenner is Morris’ certified tree inspector, and Jay Fier, one of the founding members of the city tree board, a city engineer and sometimes fondly referred to as “Mr. Tree.” Morris does have an active tree board and does celebrate Arbor Day each year, but the interest in trees and urban forestry goes well beyond a couple of individuals and a group of tree lovers. Morris’ city manager, Ed Larson, speaks proudly and confidently about the trees, parks and citizens of his community and readily ticks off the accomplishments of their urban forestry efforts. For instance, the city’s tree board. This is no ephemeral ad hoc group. In the mid-1990’s, Peter Bedker – who is now with the U.S. Forest Service in St. Paul – recommended that Morris consider establishing a tree board and provided the town with some working models and direc-

tion. In 1997, the language establishing a permanent tree board was officially inserted into the city code and now this band of six provides guidance for species selection, planting and maintenance of trees in the boulevards and parks. Diversity in the forest. Since 1998, 715 new trees have been added to the streets and parks of Morris, representing 28 different species! In addition to providing guidance on increasing the diversity of the urban forest, the tree board is actively involved with Arbor Day Celebrations. Sue Granger, a tree board member and local historian, is passionate about the community’s Arbor Day involvement. On May 5, 175 volunteers will help plant 130 new trees. And in 2008, 200 new trees are already scheduled for planting, community volunteers again providing most of the labor. Yes, the native tree population is dominated by those riparian species, but the streets and parks of Morris include some large catalpas, sturdy walnuts and magnificent silver maples, as well as many of the more recent introductions. Many of these varieties are linked to the third part of this trilogy, the West Central Research and Outreach Center (WCROC). For many years, Morris and the surrounding farms were the lucky recipients of tree species tested and released by the research station. In many ways, the urban forest of Morris was ahead of its time, compliments of that relationship. Big trees and tough love. There are a lot of very large American elms in Morris, and it’s due to a conscientious and aggressive Dutch elm disease (DED) control program. For the past several years, the more significant elms in the parks and schoolyards of Morris have been designated “heritage elms,” and have been the lucky recipients of proactive fungicide injections. But Morris’ commitment to its official city tree goes well beyond the extra care given to those lucky heritage elms. Morris has an ordinance that allows the city to pursue an aggressive sanitation program for the control of DED. If an elm becomes symptomatic, it is removed within 10 days. Regardless of placement within the city limits, public or private land, that tree must go. In addition to sanitation, the city council cost-shares the proactive

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fungicidal injections of boulevard elms with property-owners. It’s no wonder this landscape is still blessed with so many old and majestic elms. No space left behind. In an effort to diversify its urban forest, the city also has a very popular tree replacement program. Keenly aware of what an epidemic can do to a community dominated by one species, Ed Larson is concerned that many of Morris’ larger trees are Fraxinus species. With the assistance of the tree board, residents and some volunteer help, each year property owners are given a chance to have a new tree planted in their boulevard if an empty space exists. Two requirements, though: the tree must be selected from the city’s list of recommended trees, and the property owner must agree to help care for the tree. If those conditions are met, the city provides the tree and the planting labor for the installation of the new trees. In some cases, public schools students have provided that labor for areas in the parks. The bottom line: more trees are planted, the species diversity keeps improving, and the community is part of the process right from the beginning. The Gown. Quite honestly, it’s sometimes hard to tell when the line between the town and the University of Minnesota at Morris (UMM) is crossed. This is, after all, a neighborhood campus foremost. The town/gown split that is common and obvious in many smaller college communities isn’t an issue in Morris. The love and care given to the old and historic trees in the town’s urban forest is mirrored by the perspectives and actions of the campus planners and arborists. It’s an old campus, dating back to1887, when an American Indian Boarding School was established on part of the current campus. Mieka Hoffman, a UMM campus gardener and an International Society of Arboriculture Certified Arborist, exemplifies the commitment and regard for everything green that pervades the UMM grounds care department. The excitement in her voice is obvious when she offers facts about her campus: 100+ year old cottonwoods, planted by Native Americans at the American Indian Boarding School. Seventy-nine historic and newer elms still grace the 140 acres of campus

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landscape, and the 50 mature elms receive proactive fungicidal injections. Mature trees with “issues” are not summarily dismissed, removed and replaced…they are given attention and care and consideration before they’re given the axe. The tree diversity on campus is enviable. No epidemic or at least a species-specific epidemic will ever denude this campus of 900 trees. Large, healthy specimens dot the campus along with swaths of perennials, ornamental grasses and masses of shrubs. As with most campuses, all planting must live with turf grass and the fussiness of turf grass maintenance. It’s just an accepted fate on a college campus. However… All UMM grounds department gardeners must be generalists foremost, and then specialists. All must understand the maintenance requirements for turf, flowers, vines, shrubs, as well as trees. There is no maintenance practiced in isolation…which is the way it really should be. There is no “well, I don’t know about that because it’s not my job.” It is their job, and the campus shows the results of the holistic approach to landscape care.

“each year property owners are given a chance to have a new tree planted in their boulevard if an empty space exists.”

Maintaining trees and history. There is a lot at stake for the campus urban foresters. Not only was part of this campus the American Indian Boarding School, but the campus as we see it now was designed by a noted team of landscape architects. According to historian Sue Granger, in 1909 the campus became the University of Minnesota’s West Central School of Agriculture and Experiment Station, where 6,000 students attended 1910-1963. In 1960 the campus became the University of Minnesota, Morris, and a fouryear liberal arts college. The central campus, with its three layers of history, was listed on the National Register of Historic Places in 2003. From 1910-1963 the UMM campus was a testing grounds for the West Central Experiment Station’s plantings – mostly trees, ornamental shrubs, and flowers. In 1911 the West Central (now UMM) campus hired Morell and Nichols, arguably Minnesota’s most important early landscape architecture firm, to design

the campus. It is possibly their first campus plan, and their design is fairly well preserved. It’s understandable why Meika and her fellow gardeners revere the trees and campus as they do. A cavalier attitude toward old trees could wipe out more than a swath of shade. It could erase the history and efforts of a hundred years. Research and Outreach. The West Central Research and Outreach Center (WCROC) is the third story. Steve Poppe has devoted his professional life to horticulture at the WCROC. Like so many noted educators and researchers before him, he takes pride in not only the beauty of the horticultural grounds, but that so many people benefit from it each year. This profile could easily focus on this one story from Morris, Minnesota. The horticulture gardens are located at the top of “There are a lot of very large the bluff east of the UMM American elms in Morris, and campus, under the propellers of the wind turit’s due to a conscientious and bine and in a position to monitor the beauty of the aggressive Dutch elm disease Pomme de Terre river. Sheltered by an old and control program” thick planting of conifers and shrubs, the horticulture gardens are an explosive vision tucked behind those protective trees. For many years, this has been one of the premier trials gardens for annuals (650 varieties!), perennials and grasses in Minnesota. Both the infrastructure of the gardens and the plants exude attention to detail. But this is an article about urban forestry? Are there any other trees? Approximately seventy-five different species of trees may be found in the horticulture research center. That’s not a typographical error, either. Corktrees, ginkgos, Kentucky coffeetrees. Walnuts, ironwood and buckeyes. For many years, horticulturists like Harold Pellett used these grounds as trial grounds for new varieties. As they succeeded in the western climate, they thrived and were used in other landscapes. History once again permeates another Morris urban forest. New gardens, summer celebrations and short gardeners. In addition to the woody plant trials (primar-

ily windbreaks and shelterbelts), new gardens are constantly added to the horticulture area. Bailey Nurseries, Inc., recently donated a significant number of trees and shrubs, enough to begin the new woody plant arboretum display garden. A Beautiful U grant from the University of Minnesota helped provide about 400 shrubs and trees that local 6th grade science students planted locally. The project will provide years of outdoor education opportunities for these and other students in the area. The Horticulture Night (which actually goes on during daylight) is probably the single largest event of the year. For 37 years, the Research Center has hosted 1,200-1,500 people at their demonstration grounds on the last Thursday in July. Games for children, food, lecture/tours/workshops, and busloads of faithful gardeners make the trip every year. In about three hours, even avid gardeners from the Twin Cities could join the throngs, and it would be a trip worth making. There is a definite emphasis on outreach education and involvement for children at the Center, though. The Children’s Garden is the site for the fall field day, and in 2006, 650 youth attended this event. The theme was “the important roles plants play in our lives.” It gets better. In addition to that field day, twenty-four classes of kindergarten students were herded into 15 fall tours at the gardens. Kids learned about the parts of the plants that they eat, how seeds grow and how to become a butterfly. Imagine the memories they took from those tours. Finally, the Center is in the process of developing a master plan that will pull together a huge area, beginning at the Children’s Garden, winding through the woody plant demonstration area and ending in a 14 acre restored, natural prairie near the Pomme de Terre. Trails, signage and unlimited opportunities to learn, recreate and get involved. Three stories with a common theme. So, the common theme was a respect for history as well as the future, diversity and community involvement. Visit the urban forests of Morris, Minnesota soon. Gary Johnson is a Professor of Urban and Community Forestry, Department of Forest Resources, University of Minnesota.

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Urban Tree Planting and Greenhouse Gas Reductions By Greg McPherson, Ph.D.

Photo by David Hansen, University of Minnesota, Agricultural Experiment Station


everal stories have appeared recently in popular news outlets suggesting that trees are not a solution in the fight against global warming. While these pop-media pieces represent the views of a few researchers, an overwhelming body of peer-reviewed research from forest scientists around the world point to the importance of forests in reducing carbon dioxide in our atmosphere, and slowing the build-up of that greenhouse gas. The pop-media pieces include a report from Reuters (“Trees take on greenhouse gases at Super Bowl”, 30 January 2007), Dr. Ken Caldeira, a Carnegie Institute climate scientist, was reported to say, “It’s probably a nice thing to do, but planting trees is not a quantitative solution to the real problem.” Dr. Philip Duffy of Lawrence Livermore National Laboratory said, “If you plant a tree (CO2 reductions are) only temporary for the life of the tree. If you don’t emit in the first place, then that permanently reduces CO2.” Dr. Caldeira had made similar arguments previously in an op-ed in the New York Times (“When Being Green Raises the Heat, 16 January 2007). A New Scientist article (“Location is key for trees to fight

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global warming,” 15 December 2006) reports results from a study by ecologist Dr. Govindasamy Bala of Lawrence Livermore National Laboratory. The model developed by Bala and colleagues indicates that, while trees planted in tropical regions have a clear net cooling effect, trees planted in mid-latitudes may absorb so much heat from the sun that they actually contribute to warming. Because these reports fail to capture the complexity and the potential of the role that trees play in fighting global climate change, they have motivated rebuttals from the scientific community I wrote this article to assure the public that trees do indeed reduce carbon dioxide in the air, thereby reducing the warming “greenhouse” effect of the gas, and to explain that urban trees in particular are valuable because they provide that benefit in more than one way.

trees do indeed reduce carbon dioxide in the air.

First, as they grow, trees take carbon dioxide out of the air and transform it into roots, leaves, bark, flowers, and wood. Over the lifetime of a tree, several tons of carbon dioxide are taken up (McPherson and Simpson 1999). Second, by providing shade and transpiring water, trees lower

Photo by David Hansen, University of Minnesota, Agricultural Experiment Station

air temperature and, therefore, cut energy use, which reduces the production of carbon dioxide at the power plant. Two-thirds of the electricity produced in the United States is created by burning a fuel (coal, oil, or natural gas) that produces carbon dioxide—on average, for every kilowatt hour of electricity created, about 1.39 lbs of carbon dioxide is released (eGRID 2002).

Planting a tree to shade a building is something all of us can do now.

It is certainly true, as Dr. Duffy states, that not emitting carbon dioxide in the first place is a good strategy. Lowering summertime temperatures by planting trees in cities is one way to reduce energy use and thereby reduce carbon dioxide emissions. And planting trees is an immediate solution. Even if we were able to switch immediately to fuel sources that do not emit carbon dioxide, the levels in the air will remain high for decades or even centuries because of the long “lifetime” of carbon dioxide. Urban forestry doesn’t require the development of new technologies or massive investment in alternative energy sources. Planting a tree to shade a building is something all of us can do now. To address the other claims made above: Are carbon dioxide and other greenhouse gas reductions from tree planting temporary? In a sense, yes, greenhouse gas reductions are temporary if trees are removed and not replaced. To achieve long-term reductions, a population of trees must remain stable as a whole. This requires a diverse mix of species and ages so that the overall tree canopy cover remains intact, even as individual

trees die and are replaced. Although sequestration rates will level off once an urban tree planting project reaches maturity, the reduced emissions due to energy savings will continue to accrue annually. Dead trees can be converted to wood products or used as bioenergy, further delaying, reducing, or avoiding greenhouse gas emissions. Dr. Caldeira suggests in the Super Bowl article that tree planting projects are “risky.” They may appear more risky than reducing emissions by building solar or wind farms because the treerelated climate benefits are less easy to document and because the 50- to 200-year life span of a tree seems less permanent than a new power plant. This uncertainty can be offset by legally binding instruments such as contracts, ordinances, and easements that guarantee tree canopy in perpetuity. And, of course, trees and alternative energy sources are not mutually exclusive—both have a place in reducing carbon dioxide emissions. Will urban tree planting in mid-latitude cities result in zero or even negative climate benefits? Dr. Bala’s study in the New Scientist article describes two main ways trees lower temperature: they remove carbon dioxide from the air, reducing the greenhouse effect, and they release water vapor, which increases cloudiness and helps cool the earth’s surface. But because tree leaves are dark, they also absorb sunlight, which increases the temperature near the earth’s surface. The difference between trees in tropical latitudes and those in mid-latitudes has to do with the difference in how much sunlight forests reflect com-

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pared to other possible surfaces, such as grass or crops. “Shiny” surfaces reflect more sunlight back into the atmosphere than forest vegetation, resulting in less heat trapped near the earth’s surface. Large-scale tree planting projects that replace highly reflective surfaces with forests will result in more heat trapped near the ground during winter. The startling conclusion that tree planting increases global warming by absorbing more heat, especially in temperate latitudes, is based on modeling of the reflectance (albedo) of forest canopies that are darker than snow, grass, or crops and absorb more heat. The models rely on various assumptions, such as widescale afforestation – i.e. broad plantings of trees on grass and croplands. While more precise measurements may be warranted, the necessary conclusion: the earth would be cooler if the forests were cut down, defies common sense and is neither realistic nor ecologically desirable. In cities, the climate effects of incremental darkening from increased tree canopy cover is even less relevant. Asphalt, concrete, and roof surfaces account for 50 to 70% of urban areas, with the remaining area covered by trees, grass, and bare soil. The difference in the albedos of the different urban surfaces is small. Vegetation canopies have albedos of 0.15 to 0.30, the albedo of asphalt is 0.10, that of concrete and buildings is 0.10 to 0.35, and the overall albedo in low density residential areas is 0.20 (Taha et al. 1988). In cities, increasing urban tree canopy cover does not appreciably alter surface reflectance, or increase heat trapping.

At the same time, as described above, a number of field and modeling experiments have found that urban trees reduce summertime air temperatures through evapotranspiration and direct shading (Akbari and Taha 1992, Rosenfeld et al. 1998, McPherson and Simpson 2003). This reduces energy consumption and the emissions related to energy generation. Recognizing the climate benefits of trees, the California Climate Action Team Report (2006) recommended planting 5 million trees in cities to reduce 3.5 million metric tons of carbon dioxide. Our recent study found that by planting one million trees the Million Trees LA program will reduce atmospheric carbon dioxide by about 1 million tons over the next 35 years, equivalent to taking 7,000 cars off the road each year (McPherson et al. 2007). Since 1990, Trees Forever, an Iowa-base nonprofit organization, has planted trees for energy savings and atmospheric carbon dioxide reduction with utility sponsorships (McPherson et al. 2006). Over one million trees have been planted in 400 communities with the help of 120,000 volunteers. These trees are estimated to offset carbon dioxide emissions by 50,000 tons annually.

In cities, increasing urban tree canopy cover does not appreciably increase heat trapping.

Do tree-planting projects give people a “feelgood illusion that they are slowing global warming?” The climate benefits of trees in mid-latitude cities are not an illusion, although they certainly feel good. Reductions in atmospheric carbon dioxide are achieved directly through sequestration and indirectly through emission reductions. Still, planting trees in cities should not be touted as a panacea to global warming. It is one

Photo by David Hansen, University of Minnesota, Agricultural Experiment Station

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of many complementary bridging strategies, and it is one that can be implemented immediately. Moreover, tree planting projects provide myriad other social, environmental, and economic benefits that make communities better places to live. Of course, putting the right tree in the right place remains critical to optimizing these benefits and minimizing conflicts with other aspects of the urban infrastructure. The solutions to the problem of climate change are as complicated as the mechanisms of global warming itself. It is far too early and we have too little information to have decided to only invest in strategies that reduce fossil fuel emissions. Certainly we must transform the way we produce and consume energy. Doing so will require the brightest minds of science, the staunchest will of politicians, and a great deal of time, effort, and money. In the meantime, we can all plant a tree. Greg McPherson, Ph.D. is the Director, Center for Urban Forest Research, USDA Forest Service, Davis, California

References Akbari, H.; Taha, H. 1992. The impacts of trees and white surfaces on residential heating and cooling energy use in four Canadian cities. Energy. 17(2):141-149. Brahic, C. 2006. Location is key for trees to fight global warming. New Scientist. Dec. 15, 2006. Caldeira, K. 2007. When being green raises the heat. New York Times. 16 January 2007. http:// html?ex=1173502800&en=f38494123b1c3df0&ei=5070 California Climate Action Team. 2006. California Climate Action Team Report to Governor Schwarzenegger and the California Legislature. California Environmental Protection Agency. Sacramento, CA. eGRID 2002. Emissions and generated resource integrated database. U.S. EPA, version 2.01. Gardner, T. 2007. Trees take on greenhouse gases at Super Bowl. Yahoo! News. Jan. 30, 2007. http://today.reuters. com/news/articleinvesting.aspx?type=topNews&storyI D=2007-01-30T213403Z_01_N30364530_RTRUKOC_ 0_US-CARBON-SUPERBOWL-TREES.xml McPherson, E.G.; Simpson, J.R. 1999. Guidelines for calculating carbon dioxide reductions through urban forestry programs. Gen. Tech. Rep. PSW-171. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. McPherson, E.G.; Simpson, J.R. 2003. Potential energy savings in buildings by an urban tree planting programme in California. Urban Forestry and Urban Greening. 2(2): 73–86. McPherson, E.G.; Simpson, J.R.; Peper, P.J.; Gardner, S.L.; Vargas, K.E.; Maco, S.E.; Xiao, Q. 2006. Midwest Community Tree Guide: Benefits, Costs and Strategic Planting. PSW-GTR-199. Pacific Southwest Research Station, U.S. Department of Agriculture Forest Service. Albany, CA. 85 p. McPherson, E.G.; Simpson, J.R.; Xiao, Q.; Wu, C. 2007. Los Angeles One Million Tree Canopy Cover Assessment. Final Report. Pacific Southwest Research Station, U.S. Department of Agriculture Forest Service. Albany, CA. 48 p. Rosenfeld, A.H.; Akbari, H.; Romm, J.J.; Pomerantz, M. 1998. Cool communities: strategies for heat island mitigation and smog reduction. Energy and Buildings. 28:51-62. Taha, H.; Akbari, H.; Rosenfeld, A.; Huang, J. 1988. Residential cooling loads and the urban heat island—the effects of albedo. Building and Environment. 23(4):271-283.


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S YTreeSIdentification T E MandAStatistics? TICS By Dave Hanson

When you first approach a tree to determine its true identity, does statistical analysis pop into your head? Well, truthfully and thankfully, no! Not for the normal, run-of-the-mill identification. But, unfortunately, for those not so run-ofthe-mill identifications, the science of statistics is very much involved in discerning who is who and who is related to whom in the tree world. I am not fond of statistical analysis, so imagine my disappointment when the realization of the use of statistics for identifying trees became real for me. Who would have thought that statistical analysis was a foundation in tree identification technique? Identification often involves studying characteristics such as average lengths of needles, cones or petioles, average or typical widths of leaves and depth of tissues. And it is not just the simple shape that we look for in a set of leaves, but an average number of leaf lobes, sinuses or leaflets. For those mathematicians out there – look up Fibonacci and read up on his “series.” Much to my chagrin it is all too true, statistics, mathematics and tree identification go literally hand-in-hand. I was commended a while ago for cautioning a

group of new Tree Care Advisors that the characteristics often described in a tree ID book for a species may not always match up with the specimen in your hand. The brief discussion that followed centered on the fact that – statistically or typically – the description will fit the species but maybe not the individual. Almost any inter-species comparison will involve the use of statistics, but often the person performing the identification isn’t consciously aware of this subtlety. However, some comparisons will force your hand and the subtle differences between the species need to be looked at to verify true identification. For instance, consider sugar maple (Acer saccharum) and Black Maple ­— Form black maple (A. nigrum). First off, what camp do you fall into – Black maple is a true species (A. nigrum) or black maple is a subspecies of sugar maple (A. saccharum subsp. nigrum). For this discussion it really doesn’t matter, the bottom line is the unique characteristics can be divided based on statistically significant differences. Silvics of North America states that it is more often leaf characteristics than fruit, flower or winter bud characteristics that separate sugar and black maple. So, let’s take a closer look into the sugar-bush at the hard maples.

Leaves from the same tree? Leaves from the same species? Yes and Yes... Average size? Number of lobes? Prominent veins? Stipules?

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Sugar Maple (A. saccharum): Leaves: Typically, sugar maple leaves will be smooth on the upper surface and no pubescence on the underside of the leaf. Sugar maple leaves are typically 5 lobed with most text or identification books making note here that sugar maple leaves are rarely or only occasionally 3 lobed. The margins have few coarse teeth, if any and the sinuses are rounded or “U” shaped. This last statement separates sugar maple strongly from red maple (A. rubrum) which has toothed leaf margins and sharp “V” shaped sinuses.

Black Maple (A. nigrum or A. sacharrum ssp. nigrum): Leaves: Black maple is said to have prominent veins on the upper surface of the leaf while the underside of the leaf has a fine pubescence. The 3 lobes Stipules on Black Maple (usually noted that there are rarely or occasionally 5) of black maple are reported to have few, if any, coarse teeth on the margins and the lateral lobes droop from the mid-rib vein. The drooping lateral lobes give the leaf and the entire tree a wilted look. Some texts note that there are often 2 foliar stipules present at the base of the petioles. I have often found this characteristic to be present, especially on the terminal leaves. Twigs and Buds: Same brownish color with whitish lenticels, but reported to be stouter than twigs of sugar maple with larger, hairier buds.

Mostly 5-lobed sugar maple leaves. Smooth surfaces, no hairs and no stipules.

Twigs and Buds: The twigs are slender and brownish in color with whitish lenticels. Terminal buds are approximately 1/4 inch in length, lateral buds are smaller with “V” shaped leaf scars. Flower: Perfect, staminate, yellowish flowers appearing at the time of leaf-out. The flowers appear in umbel like corymbs. Fruit: Maturing in the autumn are pairs of samara – Ushaped, winged, helicopter, fruit. 5 lobed leaves, rough surface with prominent veins and stipules on black maple.

Form: Considered a medium to large tree attaining heights of 60-80 feet. Compare sugar maples description to that of black maple.

Similar twigs and buds of black maple (top) and sugar maple (bottom).

Flower: Similar to the flowers of sugar maple. Fruit: Similar to the samara of sugar maple. Form: Some textbooks state as similar to sugar maple while others list black maple as a medium sized tree up to 65 feet. Again, please keep in mind, black maple is often considered a subspecies of sugar maple. To further confuse the issue there is hybridization that takes place between black maple and sugar maple populations. So, if you want to visit these specimens for yourself, check some range maps. Then, I would suggest a trip to southern Minnesota. Not only do you have a good chance of encountering a stand of maples, but more importantly, when you do find the maples, the chances are higher that black maple will be in the mix. Note that as you move north and east in the state, black maple will drop out of the tree mix while sugar maple may still be present. Dave Hanson is a Research Specialist in Urban and Community Forestry at the University of Minnesota.


Spring 2007 • ADVOCATE

Treat your trees to a professional! By Emily Barbeau


ou may think of the trees in your yard as amenities that add shade and beauty, but they are also an investment. Keep this in mind if you are thinking about hiring someone to trim and/or remove trees from your landscape.

Strategically planted trees can save on heating and cooling costs, reduce storm water run off, attract birds, and add real estate value (not to mention joy) to your home. If you were diagnosed with a malady by a doctor, you would be told to get a second opinion before jumping into a major treatment, right? The same goes for finding a tree care company. You should hire a company who you feel comfortable working with. This means they are professional, timely, answer your questions and do not rush you into making decisions before giving you all the information you need. If you are a homeowner with trees, take a moment to read some tips on hiring a tree care company. • Think about the health and biology of the tree: Ask if a certified arborist will be overseeing the pruning work. Although the title of certified arborist is not a guarantee, it does indicate a level of professionalism in the tree care industry. • Think about safety and the risk of potential damage during tree work: Does your city require tree companies to obtain a license to work in the city? To find out, call your community’s forester or community development office. Ask for certificates of insurance, including proof of liability for personal and property damage (your property and your neighbor’s). Be sure to confirm the policy is still valid by looking at the expiration date on the certificate of insurance. Under some circumstances, you can be held financially responsible if an uninsured worker is hurt on your property or damage is done to your neighbor’s property!

Tree Care Professionals ADVOCATE • Spring 2007

• Think about where the company works and lives: Beware of individuals who go doorto-door and offer bargains for performing tree work, especially if they are not based in your area. Most reputable companies are too busy to solicit work in this manner. Improper tree care can take many years to correct and may negatively affect the health of the tree or cause it to decline. Most cities require anyone soliciting door-todoor to acquire a permit at their Community Development-Licensing Department. • Ask for local references – other jobs the company or individual has done. Take a look at some and, if possible, talk to a former client. Experience, education, and a good reputation are signs of a good arborist. • Take the time to get more than one written estimate. Require full details of the work and costs of any additional work that may be necessary. Two or more opinions and written cost estimates are worth your time and efforts. Usually, estimates are free, but expect to pay a fee and always ask before setting the appointment. Never be pressured or rushed into accepting work by apparent bargains. Never pay in advance. • A good arborist or tree care professional will offer a wide range of services (pruning, removal, fertilizing, cabling/bracing, pest control, etc…), not just tree removal.


• A professional arborist will never recommend topping a tree. They will only recommend corrective pruning, such as drop-crotch pruning, after severe damage to the crown. Decorative pruning, such as pollarding or espalier, should begin on a young tree and continued on a regular basis. Respect the tree’s natural form. • A professional, conscientious arborist never uses climbing spikes on a healthy tree. • Beware of an arborist who is eager to remove a healthy, living tree. Removal should be the last resort. -Consumer information courtesy of the National Arbor Day Foundation and the International Society of Arboriculture.

For more information, visit the following websites: 1) Minnesota Society of Arboriculture (MSA) (Certified arborist and company listing on website) 2) MN Department of AgricultureTree Care Company Registry (To confirm the company you are working with is a permanent, established company)

3) MN One Stop for Tapping into Tree Expertise (To learn about tree care) 4) Forest Resources Extension (To learn about tree care & urban forestry) Emily Barbeau is a Forester with the City of Minnetonka.

The Minnesota Shade Tree Advisory Committee’s

Monthly Forum Schedule

May: “Trees, Rain Gardens and Blooming Boulevards...A Municipal Perspective.” Presented by Mark Granlund, Arts and Gardening Program Coordinator, City of St. Paul, Division of Parks and Recreation.  See website ( for location details or call Don Mueller at 651-772-6148.          June: Urban Forestry and Water Quality.  Presented by Katie Himanga, Heartwood Consulting and Mayor of Lake City, Minnesota.          July: “Are You a Phytobigot?”  Presented by James Calkins, University of Minnesota Department of Horticulture.          August: B&B (burgers and brats) at the TRE (Teaching/Research/Extension) Nursery, St. Paul Campus, University of Minnesota. Check website ( for map to the TRE Nursery. All forums are free.  If you are an ISA Certified Arborist, you will receive 1.0 CEU for attending a forum.  All forums begin at 10:00 a.m. and conclude by 11:00 a.m.  Unless noted otherwise, the forums are held at the Minneapolis Park and Recreation Board’s headquarters at 2117 W. River Road in Minneapolis, Minnesota.

Mystery Tree Answer: Black Maple (Acer nigrum) often referred to as Black Sugar Maple (Acer saccharum ssp. nigrum).


Spring 2007 • ADVOCATE


About MnSTAC The Minnesota Shade Tree Advisory Committee (MnSTAC) was established in 1974 by a group of concerned citizens to address the health and well being of community forests. MnSTAC is recognized throughout Minnesota and the country for its expertise, advice, coordination and support for community trees. It is an organization of diverse individuals who represent a broad spectrum of tree-related interests. It fosters and supports local community tree programs across the state so healthy community forests are fully integrated into community development, infrastructure, education and management. MnSTAC Board of Directors President: Ken Simons—763/717-9366 Vice President: Michael Max, EnvironMentor Systems, Inc.— 763/753-5505 Emily Barbeau, City of Minnetonka—952/988-8421 Ken Holman, MN Dept. of Natural Resources/Forestry— 651/259-5269 Steve Nicholson, Kunde Company—651/484-0114 Gary R. Johnson, U of M/Forest Resources—612/625-3765 Robert Slater, MN Dept. of Transportation—507/529-6145 Kameron Kytonen, City of Andover—763/767-5137

Regional MnSTAC Committees Southeast STAC

Chair: Henry Sorensen—651/388-3625 or 651/385-3674 Sec./Treas.: Katie Himanga, Heartwood Forestry, Lake City —651/380-9680

Northeast STAC

Chair: Kelly Morris, City Forester, City of Grand Rapids —218/326-7481 Secretary/Treasurer/Technical Advisor: Dan Jordan, IRRRA Mineland Reclamation—218/254-7967

Calendar Events July 28-August 1, 2007, ISA Annual Conference, Honolulu, Hawaii. For more information: July 28 – August 1, 2007, American Phytopathological Society Annual Meeting, San Diego, California. For more information: September 15-19, 2007, 43rd Annual Society of Municipal Arborists Conference, Hollywood, Florida. Contact: Donald R. Goulding at or 954-304-3226.

Prairie Plants of the University of Wisconsin-Madison Arboretum. Theodore S. Cochrane, Kandis Elliot, and Claudia S. Lipke. 2007. University of Wisconsin Press Rain Gardens. Nigel Dunnett and Andy Clayden. 2007. Timber Press The Self-Sustaining Garden. Peter Thompson. 2007. Timber Press

Websites American Public Gardens

October 8-9, 2007, Restoring Native Ecosystems, Nebraska City, Nebraska. For more information:

Great River Greening

October 23-27, 2007, SAF National Convention, Portland, Oregon. For more information:

International Society of Arboriculture

October 29, 2007, ISA Leadership Workshop, Champaign, Illinois. Contact: Jerri Moorman at or 217-531-2835.

Green Roofs

Minnesota Arbor Day Minnesota Trees

November 14-15, 2007, Partners in Community Forestry National Conference, Baltimore, Maryland. For more information:

National Arbor Day Foundation

January 9-11, 2008, Minnesota Green Expo, Minneapolis, Minnesota

Tree Trust

Trees Forever

New Publications Conifers for Gardens. Richard L. Bitner. 2007. Timber Press Natural Gardening in Small Spaces. Noel Kingsbury. 2006. Timber Press ADVOCATE • Spring 2007

For handy up-to-date links to Web sites of interest, be sure to visit 15

Minnesota Shade Tree Advocate A quarterly newsletter published by the Minnesota Shade Tree Advisory Committee. Managing Editorial Group: MnSTAC Education Committee (Emily Barbeau, James Burks, Ken Holman, Gary R. Johnson, Lara Newberger, Jeff Rick, Mark Stennes, and Patrick Weicherding) Editor-in-Chief: Judy Slater Design: Creative Services Unit, MNDNR Material in this newsletter is not copyrighted. Reproduction for educational purposes is encouraged. Subscriptions are free. Articles, news items, photos and videos are welcome. This publication was produced with the support of the USDA Forest Service, Northeastern Area; State and Private Forestry. Address inquiries to: Minnesota DNR Division of Forestry 500 Lafayette Road St. Paul, MN 55155 Printed on recycled paper using soy-based inks.

Preparing Your Community for Climate and Energy Change: Opportunities for Local Sustainability Wednesday, June 6, 2007, University of Minnesota, St. Paul Campus A free conference for community leaders and concerned citizens.

Topics covered will include: • Projected climate change impacts in Minnesota • Global energy trends that can impact communities • Case studies from local governments • How to overcome barriers to action • Resources for taking action Come and learn how we can help our communities today, increase our quality of life and benefit the global environment.

More information is available at

Minnesota Shade Tree Advocate 500 Lafayette Road St. Paul, MN 55155-4044 RETURN SERVICE REQUESTED

Presorted Standard U.S. Postage PAID Permit No. 171 St. Paul, MN

Spring 2007 • ADVOCATE


uick, what comes to mind when someone mentions Morris, Minnesota? Prairie landscapes and pheasants? Wind, wide-open sightlines? Just one mor...

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