by Ryan Murphy
Our research nursery here on the University of Minnesota St. Paul campus has a variety of species including a new favorite of mine – Aronia melonocarpa (black chokeberry). “Black chokeberry is an open, upright, spreading, somewhat rounded but leggy, deciduous shrub which typically grows 3-6′ (infrequently to 9′) tall; features clusters of 5-petaled, white flowers in spring which are followed in early autumn by blackish purple, blueberry-sized fruits; and has lustrous, dark green foliage that turns an attractive purplish red in autumn” (chokeberry page). A. melonocarpa is found naturally in swampy wooded areas in North America. It can survive in both full sun and partial shade. The plant prefers a slightly acidic soil (pH 6.0 to 6.5), however, is tolerant of a wide pH range (pH 5.0 to 8.5). Aronia is a good substitute for those growers who would love to grow blueberries but do not want to deal with dropping their soil’s pH into blueberry’s preferred range (pH 4.0 to 5.0). The other awesome thing about this plant is the highly nutritious berry. The fall berries are super-rich in anthocyanins and proanthocyanidins as well as a variety of other minerals and vitamins. The visual appeal of this plant’s white flowers in the spring, attractive color in autumn, and nutritious berries make this a very exciting plant indeed. (Photos published under GNU Free Documentation License and found at commons.wikimedia.org – left photo by: BotBln and right photo by: Pawvic)
On Tuesday February 18, we began our 2014 Elm collection process. On Tuesday, we collected material to propagate new baby trees for screening from two American elm selections located on streets in the metro area. Throughout February and March, we will be rolling around the state of Minnesota to collect material from high preforming elms found in the state observed by foresters or home owners for propagation. Eventually, the baby trees propagated from cuttings and grafts will be inoculated with Dutch elm disease (DED) to see if the selection is a resistant to DED. Hopefully we will be able to find DED resistant elms that were found right in the great state of Minnesota!!
Bellow is a short photo essay of our 1st day of 2014 collections
1st American Elm collected in 2014
2nd American Elm collected in 2014
More updates on Minnesota elm collection to come!
by Chad Giblin
Team Tree’s decade-long odyssey with Olson Memorial Highway began with a Minneapolis Park & Recreation Board Arbor Day planting in the early 2000’s. This included many of the selections originally grown at the Urban Forestry Outreath & Research Extension Nursery. Since then, the median down the center of Highway 55 has become a living laboratory to track performance of many of the Dutch elm disease resistant cultivars.
The benefits of timely developmental pruning are very evident. These trees are well on their way to shading this busy metropolitan thoroughfare, without pruning at the right time and correct dose this wouldn’t be possible.\
Check out the embedded Condition Rating charts, these track overall tree quality based on a quantitative rating system meant to identify defects that detract from overall tree quality.
by Carl Blair-Broeker
Metasequoia glyptostroboides (Dawn Redwood) is a tree that looks similar to the Redwoods that grow in the Redwood National Forest (Sequoia sempervirens, Coast Redwood) and the Sequoia National Forest (Sequoiadendron giganteum, Giant Sequoia). Metasequoia glyptostroboides has a much shorter mature height of 70 to 100 feet as opposed to the record Sequoia sempervirens of 379 feet!! The foliage has a soft fern like appearance with exfoliating bark and a pyramidal form making it a perfect specimen tree where adequate space is available. Metasequoia glyptostroboidesprefers likes moderately wet soil making it a good rain garden choice.
Dawn Redwood is also a fast growing tree. This past spring in the nursery, we planted ten Dawn Redwood trees into 15 gallon containers and were about less than 1” in caliper. At the end of the season, the Dawn Redwoods had an approximate caliper of 1.5” and a stunning 2 feet of new growth! While Metasequoia glyptostroboides is of the hardiest redwood/sequoia family, it still is a zone 5 making winter hardiness in Minnesota a potential problem. Our Dawn Redwoods are currently heeled in a cozy layer of mulch for the winter to keep the roots insulated (right image). Hopefully come next spring, all ten will have survived this cold winter and will be able to be planted out in the city!
By planting unique species like Dawn Redwood in Minnesota will help diversify the urban forest. The ten trees that we will plant out in the city will be a helpful trial on how well they perform in the harsh Minnesota winters. While Metasequoia glyptostroboides is a zone 5 tree, micro climates in the city should help the likelihood of survival when extreme cold hits.
Check out some of the awesome close up images in the gallery below!!
Heeled in Trees
Dried up leaf
The benefits of trees in the urban environment are both qualitative and quantitative. Trees offer an aesthetic enhancement to the urban environment. There is something magical about driving, biking, or walking down a street lined with mature trees. There is a connection to the past – with the people who planted those trees and all the residents that have consciously or unconsciously enjoyed their presence. But in today’s society money talks. Lucky for trees – it turns out they have an economic voice – and its pretty loud.
Researchers at the USDA Forest Service, Northern Research Station have developed a tool for discovering, among other things, the economic impact that trees have in the urban environment. Its called the Urban Forest Effects (UFORE) model. This model is able to estimate the economic value of various ecosystem services provided by urban trees. For example, would you have guessed that the urban forest of Minneapolis removes around 384/tons of pollution each year? And the value of this service? $1.9 million/year. How about the current ‘hot-topic’ – carbon. Well, Minneapolis trees sequester around 8,900 tons/year – worth around $164,000/year according to the UFORE model. Urban trees also happily store this sequestered carbon for us. The Minneapolis urban forest is estimated to store 250,000 tons of carbon – a value of $4.9 million. (For more information visit http://www.nrs.fs.fed.us/tools/ufore/).
rban citizens live in highly developed and altered landscapes. We have houses connected to gas lines, sewer lines, electric lines, cable lines, phone lines, paved roads, sidewalks, and parking lots. In many cases our urban trees must coexist with these structures in close proximity. Furthermore, trees need to deal with all the construction and renovations that must be done to keep these urban systems going. Now, no one is suggesting we get rid of our modern conveniences to make room for growing bigger and better trees…well, some probably do! So we need to understand how our construction activities effect the nearby trees.
This is the goal of a 20 year study undertaken by University of Minnesota Urban and Community Forestry Professor, Gary R. Johnson. In 1993-1994 the Kenwood neighborhood of Minneapolis underwent a complete utility and infrastructure renovation. New utility lines (sewer, electric, water and gas) were run, streets were widened, curbs were lowered, new sidewalks installed, and the boulevard was regraded. The goal of the study was to see how trees planted in the area between the sidewalk and street – also known as the boulevard – performed when subjected to intensive construction activities. For comparison, a control group of boulevard trees that did not experience any construction activity was also established nearby. Five different genera of trees were looked at including maple (Acer spp.), American elm (Ulmus americana), ash (Fraxinus spp.), hackberry (Celtis occidentalis), and linden (Tilia spp.). Stem diameter (DBH) and condition ratings were taken for each tree in the study three times over the course of 20 years. Survival was also noted.
A complete statistical analysis is still forth coming but several trends are appearing from the data. For example – elm and maple trees experienced a greater percentage of loss in the construction group compared to the control group. Ash and linden on the other hand had a smaller percentage of loss in the construction group compared to the control group. Causes of tree loss are unknown. Elms by far had the greatest percentage of loss over all genera with 57% loss in the construction group and 45% loss in the control group. Average increase in DBH was not significantly different between construction and control groups among the various genera.
This represents a case study of boulevard trees in one neighborhood of Minneapolis. More studies are needed to form any definitive answer on the effect of construction on our boulevard trees. A complete report of this study is forthcoming. Stay tuned.