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Tre e C are Ad v i s o r New s l e t t e r http://

Dave Hanson and Gary Johnson, Managing Editors

Saying Goodbye to Winter!

Inside This Issue: Hoop Ash By: Dave Hanson Recipes Wanted! By: Rebecca Koetter Oak Wilt - FAQ By: Gary Johnson

March has been incredible - according to weather experts this is the first Minnesota March on record with out snowfall. I will be 2 surprised if there aren’t some temperature records on the line as well. 1


Picture Page


What can you do? TCAs Inventory and More!


Contacts and the Story Terminator Twigs have a finely chambered pith...

Volume 17 Number 1 Spring 2010

As many experts suspected emerald ash borer (EAB) has continued to raise its ugly little head in the Twin Cities. Unfortunately, this story is unfolding with a move across the Mississippi river and new finds in Minneapolis.

A group of TCAs are getting out to help prepare communities, organizations and homeowners by sharing EAB information. Are you interested in helping out? We are discussing other topics that need to be developed. 8 Let us know what you think...

Hoop Ash? Common names! An internet search yields a variety of references related to the common name hoop ash. But, the one that I am focusing on is a tree of obscurity in a way. Donald Culross Peattie writes, “ There is no disguise more baffling than the commonplace, no mystery greater than one in plain sight.” The tough and flexible wood of this tree was often used for barrel hoops; yet, woodworkers noted properties similar to the ashes and the common name “hoop ash” was coined. However, anyone familiar with the ashes in the genera Fraxinus quickly realizes that this tree does not belong there. Its identity has in a sense been shrouded by its commonness. Continued on Page 7

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Seeking recipes for the following fruits: Apple, Apricot, Blueberry, Cherry, Chokeberry, Chokecherry, Cranberry, Currant, Elderberry, Grape, Gooseberry, High-bush cranberry, Juneberry, Mulberry, Pear, Plum.

Do you Cook? Recipes Wanted!!! TCAs - Interested in a TCA Cookbook - Minnesota Grown? I’m looking for more recipes of appetizers, dinners or desserts that include edible ingredients from woody plants. So far, I have received a few recipes - but I’m still looking for more. Consider the fruits in the side bar. An example is provided below, note the additional information that will be included for each tree and shrub with a recipe. We will also include things like pH and fertilization requirements. I am still looking for more suggestions, Your ideas are awesome, welcomed and they may be included. If you’re interested in helping to research and write the care instructions, please let me know. Now, send in those recipes! Thanks in advance!



will tolerate your urban landscape. And more importantly pro-

vide early spring flowers and fruit to be enjoyed in late July into early August. Early spring blossoms are abundant and lead to a bounty of fruit. These plants are versatile and forgiving so can be a perfect fit in many landscapes! General Plant Requirements: Hardiness zone 3. Short-lived at 10-15 years Apricot variety ‘Sungold’ - A University of Minnesota release. Photo: http:// components/treefruits.asp

Soil: tolerates a range of pH, even alkali soils, prefers a well drained site.

Sun: Full sun

Pollination requirements: Requires Pruning strategy: prune for structure another apricot for cross-pollination. and to improve circulation Available Varieties: ‘Sungold’, ‘Moongold’ Fruit Ripens: Late July - August Apricot bread (source unknown)

Photo: Rebecca Koetter

2 cups sugar

2 eggs

4 cups flour

4 teaspoon baking powder

4 Tablespoon shortening

1 ½ cup orange juice

2 cups dried apricots. Cover with boiling water and set for 1 ½ hours, drain

½ teaspoon soda Mix all ingredients and put in 2 bread loaf pans. Let rise if Apricot bread. Photo: http:// Apricot-Bread

you want, 20 minutes. Bake for 55-65 minutes at 375 degrees.

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Oak Wilt in Minnesota Oak Wilt FAQs: 1.


Q. What are the “risk season” references? A. There are three Risk Season timeframes: High Risk, Low Risk and No Risk. They refer to the probability that oak wilt will infect a tree. High Risk months in Minnesota are April, May and June. Low Risk months are July, August, September and October. No Risk months are November, December, January, February and March.

Oak Wilt Update: High Risk Season starts April 1.

Q. What are these probabilities or “risks” based on? A. Three criteria are considered. First, is the fungus that actually causes the disease active? Second, is the beetle that carries the fungus to the oak active? Third, is there oak wilt in the area? If all three criteria are met, then the transmission of oak wilt from one area to another is very likely. This is referred to as “over-land transmission” of oak wilt.

3. Q. Can any beetle move the fungus from one area with oak wilt to another? A. The beetles that move oak wilt are commonly called “sap-feeding beetles.” There are only a couple of these types in Minnesota and they’re very small. 4. Q. Can an oak be infected during the Low Risk or No Risk periods in Minnesota? A. Oaks can become infected during the Low Risk period, but the probability is very low. However, since it could happen, it’s best to delay pruning of the oaks until the No Risk period or to quickly seal the pruning wounds with shellac or a water-based paint to avoid attracting the beetle if pruning during the Low Risk period is unavoidable. During the No Risk period, there is no Above: Sap-feeding beetle from the risk that an oak can become infected with oak wilt by over-land transmission Nitidulid family. of the fungus. Below: Vibratory plow line through a hard-

5. Q. Is “over-land” transmission the only way oaks can become infected with wood stand in an Anoka County Park. oak wilt? A. No. Most oak wilt is spread via root grafts. Oaks of similar species, for instance red oaks, can root graft with other oaks nearby…easily within 60-80 feet of mature oaks. When this happens, fluids can pass from one oak to another, including fluids that carry the fungal pathogen. Oak wilt spreads from one area to another (distances greater than a quarter mile or more) via the beetles carrying the fungus. Once the disease is established in a tree, it spreads from that tree to others via root grafts. 6. Q. Are all oaks affected the same way? A. The red oak group (red, black, Eastern pin, northern pin and scarlet) are more seriously affected by the disease-causing pathogen. Once infected, they do not recover and die very quickly, often within 4-6 weeks of infection during the growing season. The white oak group (bur, white, bicolor) can become infected, but they often live with the disease for a long time before dying. This lengthy period allows tree care professionals to intervene, even after infection, and can often save the trees. Continued on Page 4

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Joseph O'Brien, USDA Forest Service

Oak Wilt in Minnesota...

(continued from page 3)

7. Q. What are the best ways to either avoid or minimize the probability of oak wilt infection? A. First, avoid any wounding during the High Risk (and hopefully, the Low Risk) period…no pruning, no construction activities near the oaks. If wounding is done, whether purposely or accidentally, seal the wound quickly (within 15 minutes) with one coat of shellac (preferable) or a water-based paint. If oak wilt is in the area, it’s the High Risk season, and the wounding is unattended for more than 15 minutes, the probability of infection rises dramatically. Second, and especially important if oak wilt is established in a oak woodland, prevent the spread of the pathogen through root grafts by cutting through the connecting roots. This will need to be done by a professional, preferably a Certified Arborist and if done correctly is a very reliable technique to reduce the amount of oak wilt spread. Third, a preventative injection of a systemic fungicide can prevent infection in many cases, especially through root grafts. This should only be done by a trusted and experienced professional that is licensed to apply pesticides and ideally is a Certified Arborist. Fourth, do not move firewood from oaks that have died from oak wilt off of or on to the property in question. The red oak group in particular harbors the fungus for several months under their bark, even if they’ve been cut down. Unless the bark of oak wiltkilled oaks has been removed, that firewood needs to be used on site (burn before the next High Risk period) or covered completely. If the wood with the bark on is tarped, the tarp must be at least 40 mil. thick and preferably clear in color. The tarp should be weighted down at the ground line and sealed with soil at the ground line so no beetles can crawl in and out. Keep the wood covered for at least one full year after the tree has died. 8. Q. Once the tree becomes infected, is there any treatment? A. For oaks in the red oak group, no. For oaks in the white oak group, yes. A qualified tree care professional will prune out the dead wood (if the disease hasn’t progressed too far) and if licensed, inject the tree with a systemic fungicide. In most cases, the trees will recover if there are no other health problems affecting them. 9. Q. In areas where oak wilt has killed the oaks, should replacements be other than oaks? A. Genetic diversity is always a good way to make a forest, woodland or landscape healthier. Few insects or disease-causing pathogens kill wide varieties of trees. If the area that suffered oak wilt losses is dominated by oaks, replant with other species such as sugar maples, black cherries, hackberries, white or river birches or maybe some of the disease-resistant American elms. If oaks didn’t dominate the landscape (made up less than 10% of the tree population), some of the replacements can be oaks, especially those in the white oak group. 10. Q. Is there any other resource that can provide more detailed information and pictures of oak wilt? A. The publication “Oak Wilt in Minnesota” by David French and Jennifer Juzwik is probably the best available resource. That publication can be accessed at this url: Additionally, the Minnesota Department of Natural Resources web site has very valuable oak wilt information:

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Picture Page... 1



Bald cypress as a street tree in Ohio. Photo shared by Ralph Sievert, MPRB.


Foliage and fruit of bald cypress (Taxodium distichum) in Saint Louis, MO. Photo: Dave Hanson.

3) Photographed at Split Rock Lighthouse on the North Shore - Galls (burls) on Spruce.

Photo shared by Paul Thompson.

4) Look familiar ? Vole damage to a crabapple. The voles and rabbits were hungry this winter.

Photo shared by Pam Hartley.

5) In the woods at the Minnesota Landscape Arboretum - sapsucker damage on bitternut hickory.

Photo shared by Dave Hanson.




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What can you do?

TCAs Inventory and More!

What can you do to help your community? Think about the following needs... Projects TCAs could take on: 1. Find out what the requirements are to have a TCA booth at the 2010 Minnesota State Fair, 2. Write a letter to your community leaders advertising the TCA - EAB talk force. Currently, Bruce Allen, Glen Hambleton and Carol Mason-Sherrill are working with Rebecca and a local public access channel to produce an awareness or TCA advertisement video for distribution around the state. Do you have other ideas - we’d like to hear them! Where Do You Live? Does your neighborhood or city have an inventory? As you can see on the right - Kim Sullivan (TCA) and her husband John took on a portion of Lino Lakes and completed an ash inventory. In the fall of 2009, 4 TCA's contributed 80 hours working on an inventory for the City of Burnsville. Activities included: measuring species (DBH), noting location, assessing condition, as well as commenting on maintenance needs, defects, and other attributes on over 500 trees in four separate neighborhoods. The TCAs walked miles of streets and data was entered digitally into PDA's. The graph to the left shows the conditions by diameter class of ash trees in just one neighborhood. This information will help the City plan and finance tree management, especially ahead of EAB's arrival in the City. Burnsville is always seeking more TCA's to help with the inventory who are skilled in tree assessment, are comfortable with computers, and are available during the weekdays. Angela Hanson, Natural Resources Technician

Hoop Ash?

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(continued from page 1)

Confusion persists even when one knows the family


(Ulmaceae) where this species has been placed. Most elms (genera Ulmus) have a flattened samara while the genera Celtis that we are discussing here has drupes (a berry-like fruit). Elms don’t have a finely chambered pith, yet hackberry, nettletree, a.k.a. hoop ash (C. occidentalis) does have a finely-

chambered pith near its nodes. Several of our native elms have doubly-


serrate leaves and by the path that this discussion is following, you may have guessed already that hackberry does not. Hackberry has alternate, simple leaves that have a sharply serrate, yet singly toothed, margin. And, have you ever really looked at the bark of a hackberry tree with its warty, island-like protrusions rising from a rather gray smooth surface? Let’s not drag this confusion out any longer. Hackberry is Celtis occidentalis Linnaeus a tree native to the eastern United States including most of Minnesota. Hackberry is an adaptable species that is underutilized in our landscapes. In reference to hackberry Dirr states, “Good


tree for plains and prairie states because it performs admirably under adverse conditions,..., has the innate ability to grow in dry soils and under windy conditions.” Yet, hackberry is not a showy tree; there are no pretty flowers, there are no spectacular fall colors, and the fruit is not known to be useful to humans. So, we enjoy the shade of this durable tree that we often fail to recognize simply because we fail to look.


1) Foliage and fruit of hackberry, 2) Bark - isolated corky ridges - smooth gray in between. 3) Female (pistillate and perfect) flower - species is monoecious. 5

4) Male or staminate flower on older growth. 5) A hackberry lined street in Saint Paul.

TCA DirT Members:

Contact Phone Numbers

Bruce Allen

Chris Johnson

Polly Augustson

Rebecca Koetter

Nancy Bjerke

Heide Ludwig

Barb Gasterland

Harriet Mason

Mailing Address for Dave, Gary and Rebecca: 115 Green Hall, 1530 Cleveland Ave. North, St. Paul, MN 55108

Glen Hambleton

Carol Mason-Sherrill

Ada Hegion

Sally McNamara


Mimi Hottinger

Carol and Marty Strong

Program Contacts: Gary Johnson – 612-625-3765 or Dave Hanson – 612-624-1226 or Rebecca Koetter - 612-624-4261 or

Regional Extension Educators: Bob Mugaas— 651-480-7706 or Gary Wyatt — 507-389-8325 or Larry Zilliox — 320-762-3890 or County Contacts: Carver County (Jackie Smith) - 952-466-5309 or Dakota County (Barb Stendahl) – 952-463-8002 or Hennepin Cty (Terry Straub) - 612-596-2130 or Olmstead County (Angie Gupta) – 507-285-8250 or Ramsey County – 651-704-2063 or Scott County (Jackie Smith) - (952) 492-5410 or St. Louis County (Bob Olen) – 218-733-2870 or

Additional Reference Contacts: Debby Newman (Info-U) – 612-624-3263 Don Mueller, DNR Forestry – 651-772-6148 Ken Holman, DNR Forestry – 651-296-9110 Great River Greening – 651-665-9500

Story Terminator: We had the opportunity to rear-out an emerald ash borer in our lab. Just a few photos of the little critter... Dave Hanson


Saying Goodbye to Winter! Hoop Ash By: Dave Hanson March has been incredible - ac- cording to weather experts this is the first Minnesota Ma...