It’s finally starting to feel like spring in Detroit! Birds are singing, magnolias are blooming, and neighbors you haven’t seen in months are emerging for barbecues, clean-ups, strolls, and … tree plantings!
More than just an Earth Day photo op, tree planting builds local climate resilience, mitigating against heatwaves and floods. There is a massive need for that here–as Planet Detroit has reported, tree canopy is not equitably distributed throughout the City of Detroit, leaving formerly redlined neighborhoods more vulnerable to climate risks.
But decades-long disinvestment in municipal tree maintenance combined with poor species selection and the devastating spread of Dutch elm disease and emerald ash borer has made many residents reluctant to plant trees, afraid they will be stuck with the cost of upkeep and removal.
It is important to carefully consider site conditions and tree selection before breaking out the shovels with all this at stake. Check out our tips below, and our shorthand guide on Instagram:
What should I know before planting a tree?
Timing
Leverage the seasons to maximize your tree’s success. “Spring and fall are especially good times to transplant trees,” says arborist Peter Murray, of City Canopy Consulting. “We can take advantage of the dormant state of plant tissue and organs to minimize damage and shock … [and] best position the tree to take advantage of good soil conditions when dormancy breaks.” Watch the weather – if you miss out on the milder temperatures and rainstorms of spring, you can try again in autumn.
Assess your site conditions
Evaluate your planting site, noting the local climate, soil texture (percentages of sand, silt and clay), sun exposure, and space available for tree expansion. You can estimate climate via hardiness zones using this map developed by the USDA. The Web Soil Survey searchable map will approximate your soil texture. Armed with this site knowledge, you will be ready to pick a tree using online tree databases like those run by the Arbor Day Foundation, the Morton Arboretum, or the Missouri Botanical Garden. Murray advises, “Understanding your site and defining your objectives will narrow down the choices greatly.”
Urban and suburban areas pose additional concerns. You will want to avoid locating a tree by buried utilities (call MISS DIGG at 811 or 800-482-7171 in advance) or electrical wires. Extra care should be taken if planting near a sidewalk where tree species with aggressive roots may pose infrastructure problems and where exposure to road salt or cars may harm the tree.
The Greening of Detroit recommends over fifty species, rating each by its tolerances to salt spray, drought, and flood. Their list – by no means exhaustive – includes native species like American basswood, black gum, hackberry, and ironwood, and non-natives like dawn redwood and zelkova. While native species are good for insect and bird biodiversity, some cannot withstand the stressors of urban life and are better suited to parks, advises Fai Foen, Director of Green Infrastructure at the Greening of Detroit. Murray endorses uncommon trees such as lacebark elm, willow oak, and Persian ironwood.
For homeowners worried about damage or removal costs, or for people working with smaller easements and lots, Foen recommends choosing smaller ornamental trees and shrubs, which still provide wildlife habitat, other environmental benefits, and beauty.
Noticeably missing from Greening’s recommendations are trees that may be considered messy (ex. mulberries), smelly (ex. female gingko), disease-susceptible (ex. native elm or ash), aggressively weedy (ex. tree-of-heaven), or overly represented in the regional tree canopy (ex. Norway maple).
“The City of Detroit is very aware that the street tree inventory is 40% Acer [maple], so they’ve been diversifying since,” says Foen, pointing out that maple species are susceptible to the Asian longhorn beetle, a pest expected to spread throughout Michigan with warming temperatures. Greening is also monitoring oak wilt, a fungal disease that can be fatal to the red oak group and spreads during the growing season (which is why the safest time to prune oaks is winter), and the invasion of the spotted lanternfly. Tree diversity is crucial to fortifying the canopy against future pest outbreaks.
How will climate change affect trees on streets and in residential neighborhoods in Detroit and Michigan?
“Trees, as green infrastructure, are often discussed in two ways: to decelerate the effects, or to cope with the consequences of a changing climate,” says Murray. “A tree planted today may very likely face different conditions in the future.”
The Fourth National Climate Assessment projects that Midwestern cities will experience hotter summers, with more frequent and intense rain events. Such trends have already begun in Southeast Michigan, where daytime and nighttime temperatures have warmed and annual precipitation has increased in recent decades (1981-2010) compared to mid-century (1961-1990). Heatwaves and flooding put stress on trees. And increasing temperatures can compound threats from pests and pathogens, too.
In general, research suggests that while the potential ranges of trees will move northward, the actual ranges may likely decrease without intervention. Many urban foresters are experimenting with assisted migration – the intentional stocking of more southern-ranging trees to aid in their movement towards suitable habitat. According to Foen, Greening of Detroit uses its in-house nursery to test out how well species excelling in other cities can grow in Detroit’s environment.
What tree species are best to plant for climate change adaptation?
Predicting species’ response to climate change is tricky, but researchers have formulated some good working hypotheses as to which trees will succeed.
A 2021 study by Leslie A. Brandt and fellow forest researchers calculated adaptive capacity (or, how likely the tree will survive projected future climate) and vulnerability scores for one hundred and seventy-eight tree species and cultivars found in rights-of-ways of fourteen Midwestern cities, including Detroit. Scores were based on scientific literature and horticulture industry expertise, and applied to low and high greenhouse gas emission levels in three future time periods.
In a low-emissions scenario (“rapid reduction of greenhouse gases”), most of Detroit’s trees were on the lower end of the vulnerability spectrum. Under a high emissions scenario (“business as usual”), over half of Detroit’s trees would be considered of moderate to moderately-high vulnerability.
A glimmer of hope: two popular Detroit trees, Norway maple and Gingko, were predicted to have high adaptive capacity and low to low-moderate climate vulnerability in both emission scenarios. Natives like hackberry, Kentucky coffeetree, swamp white oak and burr oak were also projected to be highly adaptive and minimally vulnerable. Common street trees rated with medium adaptive capacity include honeylocust, sugar, silver and red maples, London planetree, sycamore, Northern catalpa, and pin oak.
Uncommon species with high adaptive capacity that may do well in Detroit included natives like black gum (flood tolerant), chinkapin oak (drought tolerant), and downy serviceberry (wide temperature tolerance). Several non-native species and cultivars were also listed, including smoke tree (drought AND flood tolerant), and disease-resistant elm cultivars.
For natural areas, consider the tree resilience toolkit developed by the Huron River Watershed Council and the Great Lakes Integrated Sciences and Assessments Center, which predicted future climate to favor species like black gum, black oak, bur oak, chinkapin oak, eastern redbud, flowering dogwood, hackberry, hickory species, honeylocust, Kentucky coffeetree, sassafras, serviceberry, tuliptree, and white oak.
Climate change will likely interact with trees to affect human health. Vibrant Cities Lab outlines some of these interactions, such as increased precipitation accelerating plant pathogens and mold allergens, or providing shade and evapotranspiration cooling. Because pollen season is increasing with climate change, some female dioecious trees may be favored in future plantings.
Using the best available science, some reasonably well-informed selections can be made. We won’t know until we try. Time will show us what works.
Where can I get these trees to plant?
Tree sales & giveaways
Check with your local conservation district, which often sells inexpensive tree saplings in early spring, or tree-focused non-profits (like the Greening of Detroit), who seasonally organize free tree giveaways.
Nurseries
Landscape Supply Inc. – Taylor, MI
Native Restoration Solutions – Chelsea, MI
Have a favorite nursery? Let us know!
I can’t plant a tree where I live – how can I get involved elsewhere?
Join a community planting or plan one for your neighborhood with one of the following organizations!
Planet Detroit’s 2022 Climate Guides are funded in part by the Americana Foundation.