Will our suburban trees survive in a warmer climate?
Q. What plants and shrubs are now being recommended for our changing climate, USDA Zone 5b?
A. We are fortunate to have some information about this because in 2016, the Northern Institute of Applied Climate Science partnered with the Morton Arboretum, the Field Museum, the Chicago Botanic Garden and the Chicago Region Trees Initiative to study how urban forest trees in the Chicago area will handle the conditions the climate models are predicting.
While this study focused on trees, the message seems to be that as we move toward a climate more in line with the historic climate of Gulf Coast states, our plants will need to handle both these conditions as well as our polar vortex-driven cold and snow, which will not be going away. Plant diversity will be key as there is no way to guarantee what will definitely survive in the future.
The study found that some favorite trees we see today in many yards, parkways and forests will not survive the future heat, humidity, ozone, precipitation, drought and insect changes predicted for our area. For example, American Linden (Tilia americana), Douglas fir (Pseudotsuga menziesii), balsam fir (Abies balsamea), Eastern hemlock (Tsuga canadesis), Norway spruce (Picea abies), paper birch (Betula papyrifera), Jack pine (Pinus banksiana) and white pine (Pinus strobus) are all considered highly vulnerable to the coming changes.
If you plant one of these trees now, the outlook for its survival is in question. Some are not recommended by the Chicago Botanic Garden in its "Trees for 2050" guide.
The NCIAS study found some native trees for this area appear to have low vulnerability, which will help our local insect, bird and wildlife populations. These include sugar maple (Acer saccharum), silver maple (Acer saccharinum), red oak (Quercus rubra), black oak (Quercus velutina), swamp white oak (Quercus bicolor), white oak (Quercus Alba), American hornbeam (Carpinus caroliniana), American sycamore (Platanus occidentalis), bald-cypress (Taxodium distichum), Eastern redbud (Cercis canadensis) and Eastern redceder (Juniperus virginiana).
The NCIAS report also lists trees that could be better suited to our area in the future because of the changing climate. These include black gum (Nyssa sylvatica), chestnut oak (Quercus montana), chinkapin oak (Quercus muehlenbergii), common persimmon (Diospyros virginiana), cucumbertree (Magnolia acuminate), mockernut hickory (Carya tomentosa), pignut hickory (Carya glabra), shumard oak (Queruc shumardii), sugarberry (Celtis laevigata) and yellowwood (Cladrastis kentukea).
The study found that some invasive species, which are nonnative plants that were either accidentally or intentionally introduced in the U.S. but cause damage to native species when they spread, appear to be well-suited to the conditions that climate change will bring. These include European glossy buckthorn (Rhamnus cathartica, R. Frangula) and Amur honeysuckle (Lanicera maackii), which are big problems in this area.
The important things to keep in mind when planning any garden is to find the right plant for the right place, choose diverse plant types, and expect that things will not always go as planned. We may all be acting as citizen scientists in the coming years as things continue to change around us.
- Nancy Degnan
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.