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Emerald Ash Borer: Sad But True, Part 2

The invasive insect appears to have weathered the polar vortex just fine.

Tom Tiddens —  April 24, 2014 — 2 Comments

In the past few months, the number one question I have been asked is “Will the cold winter have an effect on the emerald ash borer?” It’s sad but true that our cold winter will have very little effect on the emerald ash borer.

PHOTO: Emerald ash borer larva closeup.

An emerald ash borer larva lurks just under the bark of one of the Garden’s ash trees.

As we know, the emerald ash borer overwinters as larva under the bark, and that alone gives it some winter protection. More importantly, the emerald ash borer has another very interesting overwintering strategy: “supercooling.” In the fall, as the borer senses the cooler temperatures, it begins to produce a natural antifreeze that allows it to survive well below 32 degrees without freezing. The borer can also purge its stomach of materials that could freeze, flattening out and folding over. They are often found in this folded-in position under the bark in spring—I have seen this firsthand when I scraped the bark off an ash in January. Researchers in Minnesota have determined that it takes a prolonged period of about minus 25 degrees Fahrenheit or more to kill the borer. Our lows this past winter only reached about minus 16 degrees Fahrenheit (twice), as recorded by the Chicago Botanic Garden’s weather station. So, in our area, the march of the emerald ash borer continues undisturbed by our nasty winter.

PHOTO: A neighborhood ash tree with huge gaps in foliage, caused by dieoff from borer damage.

Crown die-off, due to emerald ash borer damage. Photo by Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

If you have ash on your property, I recommend monitoring closely for signs of emerald ash borer; if you don’t see signs, it is only a matter of time. When you do discover the borer, begin treatments as soon as possible. Treatments are best made proactively—before you see signs of damage on the tree! You may wish to simply plan/budget to have your trees removed. Be aware that dead ash trees are hazardous, not just for their spread of the beetle. They become brittle quickly and become a hazard as limbs fail and fall.

The Garden is a great resource if you have questions or just want to learn more about the emerald ash borer. If you have recently removed ash trees, or have already scheduled removal and are looking for replacement trees, consider our list of ash tree alternatives. Drop by our Plant Information Service with your questions! Our new location is outside the Lenhardt Library.

Click here to register online for one of two informational sessions, Emerald Ash Borer: What You Need to Know, from 10 a.m. to noon on Friday, May 16, and Saturday, May 17. This is a free seminar, but advance registration is required.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Trees for 2050

A study of suitable trees for a warming midwestern climate

Andrew Bell —  September 4, 2013 — 10 Comments

A living museum presents special challenges to its curators.

At the Chicago Botanic Garden, we not only acquire and display our collections, but we must also keep them alive and healthy. As curator of the Garden’s collection of woody plants, I’m responsible for the welfare of more than 13,000 trees. Disease, infestations, and extreme weather events are the kinds of things that keep me awake at night.

If you have recently lost a tree to emerald ash borer, you may wish to view our short list of ash replacement selections. Our full list of suggested trees for adaptive planting is linked below.

As you may know, the Garden is undertaking a ten-year plan to remove about 400 trees due to the emerald ash borer. It’s up to me to suggest suitable replacements to continue our tree legacy. To do so, I first needed to know which of the trees now growing in the Garden would continue to thrive in a warming urban environment. Thanks to a $120,000 research grant from the U.S. Institute of Museum and Library Services, we’ve been able to undertake an adaptive planting study to identify which trees will continue to thrive in Chicago’s urban forests under worst-case carbon-emissions scenarios.

Climate-change modeling indicates that some trees—those currently growing at the northern edge of their hardiness—will actually do a little bit better in slightly warmer conditions around 2020, but by 2050, ten of the 50 trees under study—20 percent—will no longer find the metropolitan area a welcoming habitat. The real concern sets in when we look at the data for 2080, which projects that only 11 of the initial trees would continue to do well in Chicago and the upper Midwest.

The trees growing along our city streets, parks, residences, and public gardens enhance the quality of metropolitan living and also play an important role in reducing greenhouse gas emissions. The cooling summer leaf canopy reduces our energy needs, and the trees themselves store significant amounts of carbon.

Our adaptive planting study suggests two key calls to action: drastically reducing carbon emission to slow climate change and help protect existing trees, and carefully selecting the trees we plant for future generations. To help both public officials and private property owners in their tree selections, the Garden has created an Adaptive Planting page on our website. There you’ll find information on a selection of 60 suitable trees for 2050.

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This project is made possible in part by a grant from the Institute of Museum and Library Services (IC-01-11-0145-11)
©2013 Chicago Botanic Garden and my.chicagobotanic.org