Tre e C a re A d v i s o r N ew s l e t t e r http:// www.mntca.org
Volume 11 Number 4
Dave Hanson and Gary Johnson, Managing Editors
Inside This Issue:
Halloween and daylight savings time are gone, Thanksgiving and Christmas are just
Sarvisstree By Dave Hanson
1 weeks away…
Quick Hits / Volunteer Opps Volunteer Hours!
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Putting Down Roots: By Cliff Johnson
3 coloration of leaves; why did trees (plants) develop this process?
Fall Colors - Warning Insects?… By Carl Zimmer
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Trees and Smog...
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Fall colors are fading and what do we really know about them? There might be more to fall coloration of leaves than just residual colors in the leaf tissues! I’ve included an article that explains some research and controversy surrounding fall On to another bit of research - trees adding to the pollution problem? Very interesting and thought provoking article… Volatile Organic Compounds and ozone components… Chad Giblin has compiled a summary of recent visits to Nicollet Island. Nicollet
Greening the Brownfield 11 Island in Minneapolis is and has been home to a brownfield study for the past four By: Chad Giblin Contacts Intro to Compass plant
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years - In my opinion it is worth a visit to see how the trees are responding…
Blooming Boulevards will be the topic of an article in January. Gary is pulling together the material already. In preparation for that I thought I would throw in a tree for such a space… Read on...
Sarvisstree When people begin talking about blooming boulevards – trees usually are not the first plants that come to mind. However, several small flowering species can really brighten up a springtime streetscape.
American Shad
Sarvisstree is one such species. This little tree produces long- pedaled white flowers just prior to or at leaf break; thus, there is a nice splash of color typically in mid to late April. The true identity of ‘Sarvisstree’ will remain elusive for another sentence or two while we explore some common names. Many of the early communities in North America relied on traveling ministers. Continued on Page 14
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Quick Hits
www.mntca.org
Tree Care Advisor website is updated at least once a month to keep material current and fresh. Areas on the page that continually change include: Stuff From the Field, TCA Tree ID and Tree Info, Bookmarks. The newest change is a bookmark to Cliff Johnson’s personal website where you can find an archive of his articles.
Dakota County: Umore Park There is progress being made at Umore Park in regards to a tree trail for teaching opportunities. However, there is still a lot of work to be done and many ideas to be implemented. The work may include removal of invasives, removal of high risk trees, mulching the trail, putting up signage and the list goes on...
Dates to put on the Calendar: See the MnSTAC calendar for upcoming details... Minnesota’s Green Expo: January 5th - 7th, 2005 in Minneapolis. Insect and Disease Threats to Minnesota Trees: February 15th and 16th, 2005 in Mankato. Minnesota Shade Tree Short Course: March 23rd and 24th, 2005 in Saint Paul.
TCA Hours… Get ‘em in ! The Umore Park trail was brushed out in August, but there remain a good number of high risk trees like those pictured
TCA’s make a difference! However, we need to let people know that we have been out in the communities, at workshops, county fairs, the state fair and every other venue that TCA’s work… 2003 TCA Hours: All Years
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I know you’re putting in the hours - so tell me!
2,209 Hours
Putting Down Roots - A column in the Chaska Herald.
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By Cliff Johnson, Carver/Scott County MG and TCA Lucky gardeners sample University’s experimental fruit varieties Article from You no doubt have heard the expression “more excited than a kid in a candy store.” We didn’t have a candy store in Gotha when I was a kid but the expression came to mind in early September as I, along with 50 fellow Carver/Scott master gardeners, toured the University of Minnesota’s research orchards and vineyards at the Arboretum’s Horticultural Research Center on Highway 5.
Fall of 2003
Two things made the tour special. First, our guide was Mike Zins, recently retired University extension horticulturist and a favorite horticultural lecturer and tour guide. The other perk was our invitation from Zins as we walked: “These are all experimental trees and vines. Sample any fruit you want and toss it aside if the flavor doesn’t agree with you.” I love fruit so sampling from the dozens of experimental pear trees laden with ripe fruit was an invitation not to be ignored. The pear trees are all crosses between Summercrisp and various Asian varieties. Each of the trees was planted 14 years ago from seed. Some pears were yellow-green and pear-shaped, while others were round (like apples), brown, red, smooth or rough. HRC fruit breeders have selected 15 top-performing trees for propagation in a nursery. Their assignment completed, these trees will be bulldozed this fall to make room for new fruit research projects.
‘Summercrisp’ maes.umn.edu
As we began the tour, Zins advised, “Some of these are pretty tasty and others...well, let’s just say you’ve got to be hungry to enjoy them.” I enjoyed most of the pears that I sampled. After the pears, our next stop was the kiwi vines. I was surprised to learn that Minnesota has a kiwi research project since I associate kiwi with the tropics. The parent stock of these vines came from Russia where the cold-hardy kiwi is grown as a vitamin C replacement for citrus, a fruit not grown in that country. The fruit on the kiwi vines we viewed is small and is eaten, skin and all. The grape-sized kiwi fruits, unfortunately, were still a month away from ripe so we couldn’t indulge ourselves at this stop. Next stop was the table grapes. The vineyard was fenced in to keep out raccoons. Judging by the indescribable juiciness and flavor of some of the experimental grapes, I can easily understand the desire to deter raccoons. Like the pear research, the goal here is to find Minnesota-hardy grape varieties that will provide growers with a tasty grape for Minnesota consumers. Following my feast of pears, and somewhere between the grape and apple
‘Swenson Red’ maes.umn.edu
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Putting Down Roots ... stops, I pondered the consequences of sampling as many apples as I had pears. My thoughts weren’t pretty, so I limited my apple tasting to a half dozen varieties. How do you know when an apple is ripe? Zins was asked. It depends, he explained, on the apple variety, the growing season, fall temperature and other factors. Varieties like Hazen, State Fair and Beacon mature early and can be picked in August or early September. Later varieties like Haralson, Regent and Fireside get sweeter the longer they hang on the tree and don’t need to be picked until after the first light frost. One way to gauge ripeness is to cut the apple in half. If the seeds are dark (black or brown), the apple is close to ripe.
‘Regent’ Photo: maes.umn.edu
The goal of all of these research efforts, of course, is to discover fruit that will perform in Minnesota gardeners’ yards and commercial growers’ orchards and vineyards. There have been many past successes so it’s a safe bet that some of the pears, grapes and apples I sampled will become the hot varieties of 2010 or 2015. One of the University’s most notable fruit-breeding successes is the Honeycrisp apple, which disappears off shelves almost as fast as the juicy red apples can be stocked. Honeycrisp is described as “pure good taste...aromatic, clean, sweet-tart...along with juiciness, versatility, excellent ‘snap,’ and the unusual ability to be refrigerated for six months with no loss of its outstanding features.” During its research years (1960s), Honeycrisp was known as “Minnesota 1711,” a cross between Macoun and Honeygold. Honeygold, in turn, was a cross between Golden Delicious and Haralson, both of which were developed at the University of Minnesota.
‘Honeycrisp’ Photo: maes.umn.edu
Growing fruit in Minnesota requires more management and care than growing ornamental woody plants and perennial flowers. The rewards for those who follow proven growing guidelines, however, can make it all worthwhile, especially at harvest time. The University’s horticulture extension website contains lots of cultural information. It can be viewed at http://www.maes.umn.edu/ HardyPlants.asp Photos from University of Minnesota’s Agriculture Experiment Station Website: http://www.maes.umn.edu/ Photographer: Dave Hansen, University of Minnesota Agriculture Experiment Station
‘Haralson’ Photo: maes.umn.edu
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Those Brilliant Fall Outfits May Be Saving Trees (Posted: 19-Oct-04) From the New York Times, By Carl Zimmer As trees across the northern United States turn gold and crimson, scientists are debating exactly what those colors are for. The scientists do agree on one thing: the colors are for something. That represents a major shift in thinking. For decades, textbooks claimed that autumn colors were just a byproduct of dying leaves. "I had always assumed that autumn leaves were waste baskets," said Dr. David Wilkinson, an evolutionary ecologist at Liverpool John Moores University in England. "That's what I was told as a student." During spring and summer, leaves get their green cast from chlorophyll, the pigment that plays a major role in capturing sunlight. But the leaves also contain other pigments whose colors are masked during the growing season. In autumn, trees break down their chlorophyll and draw some of the components back into their tissues. Conventional wisdom regards autumn colors as the product of the remaining pigments, which were finally unmasked. In other words, autumn leaves were a tree's gray hair. But in recent years, scientists have recognized that autumn colors probably play an important role in the life of many trees. Yellow leaves get their color from a class of pigments called carotenoids. Another group of molecules, anthocyanins, produce oranges and reds. Trees need energy to make carotenoids and anthocyanins, but they cannot reclaim that energy because the pigments stay in a leaf when it dies. If the pigments did not help the tree survive, they would be a waste. What's more, leaves actually start producing a lot of new anthocyanin when autumn arrives. "The reds are not unmasked-they are made in autumn," said Dr. David Lee, a botanist at Florida International University. Evolutionary biologists and plant physiologists offer two different explanations for why natural selection has made autumn colors so widespread, despite their cost. Dr. William Hamilton, an evolutionary biologist at Oxford University, proposed that bright autumn leaves contain a message: they warn insects to leave them alone. Dr. Hamilton's "leaf signal" hypothesis grew out of earlier work he had done on the extravagant plumage of birds. He proposed it served as an advertisement from males to females, indicating they had desirable genes. As females evolved a preference for those displays, males evolved more extravagant feathers as they competed for mates. In the case of trees, Dr. Hamilton proposed that the visual message was sent to insects. In the fall, aphids and other insects choose trees where they will lay their eggs. When the eggs hatch the next spring, the larvae feed on the tree, often with devastating results. A tree can ward off these pests with poisons. Dr. Hamilton speculated that trees with strong defenses might be able to protect themselves even further by letting egg-laying insects know what was in store for their eggs. By producing brilliant autumn colors, the trees advertised their lethality. As insects evolved to avoid the brightest leaves, natural selection favored trees that could become even brighter. "It was a beautiful idea," said Marco Archetti, a former student of Dr. Hamilton who is now at the University of Fribourg in Switzerland. Dr. Hamilton had Mr. Archetti turn the hypothesis into a mathematical model.
The reds of fall - Anthocyanins Top: Freeman Maple Center: Red Oak Bottom: Euonymus or burning bush Photos: Dave Hanson
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The model showed that warning signals could indeed drive the evolution of bright leaves at least in theory. Another student, Sam Brown, tested the leaf-signal hypothesis against real data about trees and insects. "It was a first stab to see what was out there," said Dr. Brown, now an evolutionary biologist the University of Texas. He studied 262 tree species, noting the leaf color and number of aphid species specialized on them. Dr. Brown found that trees with bright autumn leaves tended to be the victim of more specialist aphids. The correlation supported the leaf-signal hypothesis. Dr. Hamilton did not argue that the evolution of leaf signals would make all trees brilliantly colored. Instead, he said, only species that were under heavy attack experienced this evolutionary pressure.
Sugar Maple - Fall colors of golds and reds - Anthocyanins Photo: Dave Hanson
Dr. Hamilton died in 2000 at 63 as a result of complications from malaria he contracted while doing research in Africa. Only after his death did Dr. Archetti and Dr. Brown publish their collaborations with their mentor. The leaf-signal hypothesis was so provocative that other biologists began to test it. Dr. Snorre Hagen of the University of Oslo and colleagues studied a dozen mountain birch trees over three years, observing factors like brightness of leaves each fall and the level of insect damage the next spring. They found that birches with strong colors in the fall tended to suffer less damage from insects the next spring. Dr. Archetti is also testing the leaf-signal hypothesis. Working with Dr. Simon Leather, an entomologist at Imperial College London, he has observed aphids laying eggs on bird cherry trees in the fall. As he reported in May in The Proceedings of the Royal Society of London, aphids prefer leaves that are still green, rather than yellow or red leaves. "This is the first basic prediction of the hypothesis, that aphids are more abundant on dull leaves," Dr. Archetti said. While evidence from such studies is preliminary, Dr. Hamilton's students are encouraged. "It is supportive, but far from being robustly conclusive," Dr. Brown said. The leaf-signal hypothesis has also drawn criticism, most recently from Dr. Wilkinson and Dr. H. Martin Schaefer, an evolutionary biologist at the University of Freiburg in Germany. In a paper to be published in Trends in Ecology & Evolution, Dr. Schaefer and Dr. Wilkinson argue that autumn colors are not sending messages to insects. It's wrong, but compelling, Dr. Wilkinson said. Dr. Wilkinson and other critics point to a number of details about aphids and trees that do not fit Dr. Hamilton's hypothesis. Dr. William Hoch, a plant physiologist at the University of Wisconsin, argues that bright leaves appear on trees that have no insects to warn off. "If you are up here in the north in Wisconsin, by the time the leaves change, all the insects that feed on foliage are gone," Dr. Hoch said.
Black Walnut - Fall color is bright yellow - Carotenoids Photo: Dave Hanson
In their article, Dr. Schaefer and Dr. Wilkinson argue that a much more plausible explanation for fall colors can be found in the research of Dr. Hoch and other plant physiologists. Their recent work suggests that fall colors serve mainly as a sunscreen. The interior of an autumn leaf is a frenzy of activity. Much of the chlorophyll and other equipment necessary for photosynthesis is being carefully dismantled, while the nutrients it contains, like nitrogen and phosphorus, are shipped into the tissue of the tree. The tree will need those nutrients to grow and reproduce in the spring. The leaves need energy to send these reserves into the tree, which they can only get through photosynthesis. But because they have dismantled much of their light-harnessing
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equipment, it no longer works efficiently. Autumn leaves cannot capture all the sunlight striking them, and the leftover energy can build up in the leaf and cause damage to its tissue. "Sunlight in October isn't near as intense as in July," Dr. Hoch said, "but it can do more harm to a leaf." Anthocyanins, the pigments that produce red and orange colors, appear to protect autumn leaves by blocking some of the sunlight. Dr. Hoch and his colleagues have found the most compelling evidence for this role. They raised normal trees along with mutants that could not produce anthocyanins. While the mutants thrived in a greenhouse, they could not ship nutrients out of their leaves in autumn sunlight. Many plant physiologists see the protection provided by pigments as so important that there is not much left over for Dr. Hamilton's leaf-signal hypothesis to explain. "You may have a few instances where insects have some sort of relationship to color changes," Dr. Hoch said, "but it's almost certainly not a broad-based explanation. It doesn't hold any water." Dr. Wilkinson speculates that some of the recent evidence in favor of Dr. Hamilton's signal hypothesis actually supports the sunscreen hypothesis. The link Dr. Hagen found between bright fall leaves and a lack of damage in spring may not be a result of trees' warning insects. Instead, the bright leaves might belong to trees that were doing a good job of protecting their leaves as they prepared for winter.
Virginia creeper - It is not just the trees that produce vibrant fall colors like these deep reds. Photo: Dave Hanson
These arguments have not swayed Dr. Hamilton's former students, who argue that the leaf-signal hypothesis is still worth investigating. Dr. Brown believes that leaves might be able to protect leaves both from sunlight and from insects. Dr. Brown and Dr. Archetti also argue that supporters of the sunscreen hypothesis have yet to explain why some trees have bright colors and some do not. "This is a basic question in evolution that they seem to ignore," Dr. Archetti said. "You go to a forest, you see one tree is red and another is green. Why? They cannot explain this point." "I don't think it's a huge concern," Dr. Hoch replied. "There's natural variation for every characteristic." Still, the plant physiologists have more work to do. Some trees, like birch, produce no anthocyanins. Their yellow leaves are produced by carotenoids. During the growing season, carotenoids help chlorophyll absorb sunlight, but in the fall they do not shield the leaves. Dr. Hoch suspects that trees with yellow leaves must have some other way to protect their leaves in autumn, which he is now trying to find. Meanwhile, Dr. Archetti and Dr. Brown hope they can stimulate more experiments to test the leaf-signal hypothesis. "There are a series of steps you'd want to investigate on the tree side and the insect side," Dr. Bur Oak - Fall color produced Brown said. Dr. Hamilton's students and their critics agree that the debate has been useful, by tannins and the result s are because it has given them a deeper reverence for this time of year. brown tones.
"People sometimes say that science makes the world less interesting and awesome by just explaining things away," Dr. Wilkinson said. "But with autumn leaves, the more you know about them, the more amazed you are." NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving this information for research and educational purposes.
Photo: Dave Hanson
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Study: Emission of Smog Ingredients From Trees is Increasing Rapidly (Posted: 07-Oct-04) http://www.eurekalert.org/pubnews.php , US Department of Energy Science News Changes in forestry and agriculture affecting ozone pollution Two major sources of smog-producing chemicals are automobile tailpipes and natural emissions from tree leaves. Postdoctoral researcher Drew Purves found that land use practices have altered the mix of trees across the landscape, greatly increasing the contribution from trees. One of the greatest producers is the sweetgum species, such as those along Washington Road. Changes in U.S. forests caused by land use practices may have inadvertently worsened ozone pollution, according to a study led by Princeton University scientists. The study examined a class of chemicals that are emitted as unburned fuel from automobile tailpipes and as vapors from industrial chemicals, but also come naturally from tree leaves. These chemicals, known collectively as VOCs, react with other pollutants to form ozone, a bluish, irritating and pungent gas that is a major form of smog in the lower atmosphere.
VOCs volatile organic compounds
While clean-air laws have reduced the level of man-made VOCs (volatile organic compounds), the tree-produced varieties have increased dramatically in some parts of the country, the study found. The increase stems from intensified tree farming and other land use changes that have altered the mix of trees in the landscape, said Drew Purves, the lead author of the study that included scientists from four universities. "There are seemingly natural but ultimately anthropogenic (human-caused) processes in the landscape that have had larger effects on VOC emissions than the deliberate legislated decreases," said Purves. Although scientists knew that trees contribute substantial amounts of VOCs to the atmosphere, the rate of increase in recent decades was previously unrecognized. "If we don't understand what's going on with biogenic (plant-produced) VOCs, we are not going to be able to weigh different air-quality strategies properly," said Purves. "It's a big enough part of the puzzle that it really needs to go in there with the rest." The study may help explain why ozone levels have not improved in some parts of the country as much as was anticipated with the enactment of clean-air laws, Purves said. Environmental technologies such as catalytic converters and hoses that collect fumes at gas pumps have substantially reduced human-produced VOCs. However, in some parts of the country -- particularly the area extending from Alabama up through the
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Tennessee Valley and Virginia -- these improvements may have been outweighed by increased VOC emissions from forests, mainly because of tree growth in abandoned farmland and increases in plantation forestry. Purves emphasized that cutting the human-caused sources may have been worthwhile even if ozone levels did not decrease. "Even keeping the air quality the same might have been an achievement because if we hadn't done anything it might have worsened," said Purves. The study did not measure actual ozone levels. Instead it focused on VOCs, a crucial part of the chemical reaction that produces ozone. The other critical ingredient is a class of gasses known as NOx (various combinations of nitrogen and oxygen), which are almost entirely man-made. The ozone-producing reaction happens most readily in hot weather, which is also when trees produce the most VOCs. Further studies at Princeton and the federal Geophysical Fluid Dynamics Lab at Princeton are using sophisticated computer models to estimate the changes in ozone caused by the changes in tree-produced VOCs. Purves noted that interactions between VOCs, NOx and ozone are complex -- some may actually lower pollution -- so it would be premature to base environmental policy on studies of VOCs alone. Purves, a postdoctoral fellow, wrote the article in collaboration with Stephen Pacala, professor of ecology and evolutionary biology at Princeton, as well as John Casperson of the University of Toronto, Paul Moorcroft of Harvard University and George Hurtt of the University of New Hampshire. The article is scheduled to be published later this fall in the journal Global Change Biology. The scientists conducted the study by analyzing data collected by the U.S. Forest Service, which measured and cataloged 2.7 million trees on 250,000 plots of land across the country. They calculated the VOC emissions for each tree and each plot and used their findings to map VOC levels nationally. The scientists compared survey data taken in the 1980s with those taken in the 1990s to determine how levels were changing over time. They found that areas where farmland has been abandoned during the last century have early generations of trees that produce higher levels of VOCs than older growth forests. In the South, pine plantations used for their fast-growing supplies of timber have proven to be havens for sweetgum trees, which are major producers of VOCs. Indeed, virtually every tree that grows fast -- a desirable quality for forestry
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production -- is a heavy emitter of VOCs. "It's just one of those biological correlations," said Purves. "What you want is a fastgrowing tree that doesn't produce a lot of VOCs, but that doesn't seem to exist." The findings also could raise questions about potential strategies for developing "green" fuels. One idea for cutting greenhouse gas emissions is to create "biofuels" from renewable tree plantations; however, these plantations may lead to increased ozone levels, the authors note. The findings lend support to proposals among environmentalists to shift attention to regulating NOx, the other main ingredient for ozone. They also underscore the pervasive effect of human activities on the environment, because something as seemingly benign as planting forests can have a substantial impact. "You can't identify any of these processes as 'natural,'" said Purves. "The idea of natural versus human-caused is disappearing. Ten years from now, woodlands may have more of one species than another, and you could call that natural change. But here in New Jersey, the mix of trees is affected by the population of deer, and they are entirely under our control. In other parts of the country, it is the fire-suppression policies." Noting President Ronald Reagan's notorious 1980 reference to trees causing pollution (Reagan said: "Approximately 80 percent of our air pollution stems from hydrocarbons released by vegetation."), the authors conclude: "The results reported here call for a wider recognition that an understanding of recent, current and anticipated changes in biogenic VOC emissions is necessary to guide future air-quality policy decisions; they do not provide any evidence that responsibility for air pollution can or should be shifted from humans to trees." NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving this information for research and educational purposes.
So, it appears to be a little more complicated than our basic understanding and chemical reaction statement for photosynthesis! 6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2
Greening Up the Brownfield
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Tree Performance on Nicollet Island Chad Giblin and Jeff Gillman Department of Horticultural Science University of Minnesota What’s a Brownfield? A brownfield is a site that has unusually harsh climate and soil conditions and is considered generally unsuitable for plant growth. Many brownfields are the result of contamination from old dumps, construction sites, and staging areas. In recent years
Typical conditions on Nicollet Island – hot, open, and dry
there has been a lot of interest in rejuvenating these sites for both public and private use. One of the major objectives is to identify landscape plant species that can tolerate these hostile conditions. There are numerous local, state and federal organizations that specialize in reclaiming these areas. Just do an internet search for “brownfield”, you’ll be surprised at what you find. Brownfields are usually dominated by weeds and other invasive species. Like most others, the brownfield on Nicollet Island has extremely poor soil properties. Texture is quite variable but usually contains a fair amount of gravel, sand, clay, and other “non-soil” components. Soil pH is very high, ranging from 7.9 to 8.6 with organic matter very low at less than 0.5%. Project History In 1999 a group of cooperators from the Minneapolis Park and Recreation Board, Tree Trust, and the University of Minnesota initiated a plan for planting trees on Nicollet Island. By planting time in 2000, they had selected 15 different species and cultivars with a total of 183 trees to be planted. Data Collection Caliper and stem growth rate are measured annually. Mortality, winter injury, stem and canopy condition ratings are also measured every year. Condition ratings are based on a subjective quality assessment on a four-point scale (4=highest to 1= lowest rating).
An example of the “soil” found on Nicollet Island
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Tree Performance In most cases the trees either performed very well or quite poorly. All of the ash varieties did very well; overall mortality after four years was around 5%. Other species at the top include: hackberry, Autumn Blaze Freeman maple, and Triumph elm. These all had no mortality. On the other hand, Fall Fiesta sugar maple and Green Column black maple both had some issues. After four years, both had mortality around 50% with overall stem and canopy condition below other species. Heritage oak, Boulevard linden, Kentucky coffeetree, Amur maackia, and bur oak all fell into the 15 to 25% mortality group after four years. The Planting Depth Issue After planting, many trees were found to have been planted too deep on-site. After a close examination the trees were found to be too deep in the container even before planting! Overall, 99 trees were lifted and corrected to get the first main order root at or near the soil line. This correction involved lifting the trees, removing excess media and pruning off any adventitious roots. You might expect this to really stress these trees and increase mortality; in most cases the opposite was true. Two out of three times the mortality for corrected trees was lower than that of the overall species mortality. This procedure, especially for container-grown or containerized trees, shows a lot of promise for correcting deeply planted trees. This spring at the TRE Nursery, we planted out 50 containerized Cathedral elms after removing 6 to 8� of excess media from over the root system. In many cases this left us with 50% or less of the original soil ball. Thus far, we have had no mortality in these trees. This process, while time-consuming, can be of critical importance when planting out container stock that is planted too deeply in the nursery can. Hardiness and Tough Sites There is a lot of concern about the winter hardiness of some of the white ash cultivars. Autumn Purple, in particular, has had a number of problems with winter stem injury like frost cracks and frost cankers, especially with smooth-barked, young trees. Interestingly enough, there has been no incidence of winter stem injury on this or the other ash cultivars on Nicollet Island. Dr. Pellett theorized that this might actually be due to the tough conditions of the site! In many cases we see the trees on Nicollet Island going dormant in the fall prematurely. This may allow them additional acclimation time before winter sets in. Highly vigorous trees, growing in better conditions may have acclimation timing issues causing them to be more susceptible to winter injury.
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The Nursery Grower Connection These brownfield sites offer valuable insight into future demand for urban trees. Commercial and residential development is expanding at an incredible rate generating numerous new customers for Minnesota’s nursery growers. In these new developments soil pH is often high and drainage can be poor due to construction pressures. Furthermore, the climate is often harsh due to open, windswept conditions. By tracking tree vigor on Nicollet Island and other brownfield sites we can make confident recommendations for trees to use in new developments for both customer satisfaction and long-term tree performance and health. A full presentation of the results is now posted on the TRE website at: http://www.tre.umn.edu/growers/growers.htm Research Cooperators: University of Minnesota – Department of Forest Resources Gary Johnson
Dave Hanson
Minneapolis Park and Recreation
‘Autumn Blaze‘ - Freeman Maple
Board
University of Minnesota – Department of Horticultural Science Jeff Gillman
Harold Pellett
Chad Giblin
DeLasalle High School Nicollet Island Community
University of Minnesota – Minnesota Extension Service Tree Trust
Patrick Weicherding
Table 1: Tree Species Used on Nicollet Island
Acer nigrum 'Green Column' Acer rubrum x saccharinum Acer Saccharum Celtis occidentalis Fraxinus americana 'Autumn Blaze' Fraxinus americana 'Autumn Purple' Fraxinus nigra 'Fall Gold' Fraxinus nigra x mandshurica 'Northern Gem' Fraxinus nigra 'Northern Treasure' Gymnocladus dioicus Maackia amurensis (male only) Quercus macrocarpa x robur 'Heritage' Tilia americana 'Boulevard' Quercus macrocarpa Ulmus hybrid 'Accolade'
‘Autumn Purple’ - White Ash
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Above: Flowers and new leaves
History suggests that as the sarvisstree bloomed in the spring the ministers would be making the first visits and holding memorial services for communities that had been snowbound through the winter. Some forms of the story push further and suggest that the bloom of the ‘servicetree’ or ‘serviceberry’ occurred as burial sites were prepared for loved ones lost during the winter months. Sarvisstree or Sarvissberry as told by Donald Culross Peattie, is the true form of the name and was derived from a Roman transformation of Sorbus. Sarviss was derived by Shakespearean English from the true Latin. So, Peattie goes on to state that ‘serviceberry’ is likely a corrupted form of the true name ‘sarvissberry.’
on May 2nd. Below: Single stem specimens in a mass planting Photos: Dave Hanson
Berries or pomes - early July. Photos: Dave Hanson
We can’t stop there however, the American shad, yes, a fish, returns from the Atlantic Ocean to spawn in the rivers of the East Coast sometime between February and June. This is dependent on the temperature of the rivers to which the fish will migrate for spawning. It is probably pretty safe to say that there is a complex relationship between air, soil and water temperatures that drive the timing of the shad run and the blossoming of the ‘shadbush’ – a.k.a. ‘Serviceberry’ or ‘Sarvisstree.’ Hang on, we can’t leave it here, because sometime in June the wildlife begin a feeding frenzy as they go after a small tree or shrub that is producing numerous, dark purple or blackish fruits (pomes). Bears, birds, chipmunks and even fox are out there in the wild competing for these tasty morsels on the ‘Juneberry’ – a.k.a. ‘Shadbush’, ‘Serviceberry’ or ‘Sarvisstree.’ . If a hiker happens along at the right time and the woodland creatures haven’t discovered the berry crop yet, a tasty treat may be had.
Alright, common names exhausted – let’s delve in to the details of Amelanchier spp. According to Harlow and Harrar’s Textbook of Dendrology there are 33 species of Amelanchier across the United States and Canada and every state and province has at least one species growing within its borders. Minnesota Trees has three species listed for Minnesota; Amelanchier arborea (Downy serviceberry), A. sanguinea (Roundleaf serviceberry), and A. alnifolia (Saskatoon serviceberry). In Minnesota amelanchier is considered a shrub or small tree with a narrow to
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rounded crown obtaining heights of 6-25 feet and trunk diameters up to 10 inches. The branching pattern is alternate and the leaves are simple with finely toothed margins. One of the unique characteristics is that the leaf margins are typically entire in the bottom third of the leaf. Couple this trait with the sharply pointed, scaled reddish bud and the genus is pretty easy to separate from other shrubs. However, distinguishing the species can be challenging and somewhat problematic due to natural variations and hybridization. The twigs are typically reddish-brown ending with a true terminal bud. As the bark matures it develops a light gray color. The flowers appear early in the spring on a trailing raceme and are typically white in color. Along about June the fruit or pome ripens to display a dark purple to black color. The fruit of Juneberry or amelanchier is cultivated in Canada and it is used in jams, jellies and even in pies. Michael Dirr in his Manual of Woody Landscape Plants lists a number of varieties that are commercially available. One that is outstanding is ‘Autumn Brilliance’ and as the name denotes the fall colors of gold to red are spectacular. One note that Dirr puts forth is that fall color on all amelanchier species is variable from year to year.
Flowers on May 6th Photo: Dave Hanson
Serviceberry or amelanchier species are proving to be good performers on boulevards. The single stem specimens can tolerate some of the harsh boulevard conditions and are relatively free of insect and disease pressure. However, Dirr points out that where amelanchier shine the best are in mass plantings, woodland edges, and along ponds or streambanks. So, if you are looking to create a bloomin’ boulevard consider a small tree like amelanchier. Fall colors
Photo Dave Hanson
Berries or pomes - above photo mid-June and below early July. Photos: Dave Hanson
Contact Phone Numbers
TCAAG Members:
Program Contacts:
Bob Condon – 952-890-1228
Mimi Hottinger – 507-388-4838
Gary Johnson – 612-625-3765 or grjonson@.umn.edu Dave Hanson – 612-624-1226 or dlhanson@umn.edu Mailing Address: 115 Green Hall, 1530 Cleveland Ave. North, St. Paul, MN 55108
Paula Denman – 612-338-1871
Lisa McDonald - 612-721-2672,
Laurie Drolson – 651-464-9829
Betsy McDonough - 651-779-0437
Bruce Granos – 952-423-5211,
Lu Schmidtke - 651-455-6125
Contacts: Regional Extension Educators: Bob Mugaas – 651-480-7706 Patrick Weicherding, – 763-767-3836 or weich002@umn.edu Gary Wyatt, 507-389-8325 or wyatt@umn.edu County Contacts: Carver County (Jackie Smith) - (952) 442-4496 or smith515@umn.edu Dakota County (Barb Stendahl) – 952-463-8002 or stend004@umn.edu Olmstead County – 507-285-8250 Ramsey County – 651-777-8156 Scott County (Jackie Smith) - (952) 492-5410 or smith515@umn.edu St. Louis County (Bob Olen) – 218-726-7512
Additional Reference Contacts: Debby Newman (Info-U) – 612-624-3263 Don Mueller, DNR Forestry – 651-772-6148 don.mueller@dnr.state.mn.us Ken Holman, DNR Forestry – 651-296-9110 ken.holman@dnr.state.mn.us Paul Walvatne MNDOT – 651-284-3793 Paul.Walvatne@dot.state.mn.us Great River Greening – 651-665-9500 Tree Trust – 651-644-5800
Left: Compass plant (Silphium laciniatum) Bottom Right: Cup plant (Silphium perfoliatum) Photos: Dave Hanson - For full color images go to www.mntca.org and the current newsletter.