Tips for planting trees that will thrive in the midst of climate changes
By Megan Plete Postol
The changing climate has shifted weather patterns in small ways. Those minor changes, over time, have begun to affect the landscape of the Adirondacks.
A warmer world affects trees in myriad ways. According to Paul J. Hetzler, a certified arborist and a former Cornell Extension educator, record wet seasons, such as in 2013, 2017, and 2019 allow normally weak foliar pathogens to spread and flourish, becoming primary agents of mortality. Needlecast diseases are killing more conifers than ever before, while anthracnose of maples, walnuts, and other deciduous species is also on the rise.
Recent drought years, such as the years 2012, 2016, 2018, caused the lowest soil-moisture readings ever recorded in the region. Root systems died back greatly, making trees more vulnerable to pests and diseases for years afterward. In some places, extensive death of red oaks and sugar maples occurred when drought years followed on the heels of defoliation by tent caterpillars or spongy moths.
Longer seasons and milder winters allow invasive forest pests to move north faster than was thought possible. Hemlock woolly adelgid, oak wilt, and emerald ash borer are a few examples.
Trees for variable conditions
It might seem insurmountable, but there are actions that Adirondackers can take to combat the effects of climate change, starting in the backyard. Hetzler has a few suggestions, starting with careful consideration of which trees to plant.
Hetzler’s picks include some non-regional trees and some tough local characters that deserve to be more widely planted.
The ginkgo (Ginkgo biloba) can withstand severe drought, high soil pH, salt, and air pollution, he said. Once trained, it is low-maintenance in terms of pruning. The Japanese tree lilac is another familiar urban tree that is often underrepresented in our landscapes. Aside from its lush blooms, it is perfect for under utility wires. In addition, it is largely pest and disease-free, and requires little maintenance pruning.
Hetzler said the Norway spruce is a good choice. Although not drought-tolerant, is very resistant to needlecast diseases that are decimating Colorado blue and other spruce species.
The Kentucky coffeetree is non-native to the region but is cold-tolerant, drought-resistant, and withstands air pollution and soil pH up to about 8.2. Ornamentally, Hetzler said its coarse bark and ascending branch habit give all-season interest. Another non-native to consider is the northern catalpa, which is moderately drought-tolerant and can survive intermittent flooding as well. Thornless common honeylocust and native hackberry are another two that Hetzler recommends.
Heztler’s favorite pick is bur oak. With a species lifespan of 800+ years, it is a true legacy tree, he said.
“It’s super drought-tolerant, yet fine with seasonal flooding,” Hetzler said. “It can be hard to get established, so the smaller the better for transplant stock.”
Trees to avoid
There are a few varieties Hetzler suggests avoiding. The first is Colorado blue spruce, which he said is incredibly vulnerable to needlecast diseases. Katsura trees are another because they cannot tolerate even moderately dry conditions. White-barked birches are sitting ducks for the invasive bronze birch borers, Hetzler said, which are lethal unless caught early and treated systemically. Birch should be used only rarely in most Adirondack landscapes. Hetzler recommends river birch as a good substitute for white-barked birches, as they are more accepting of landscape conditions and are rarely attacked by bronze birch borers. River birch are not drought-tolerant, but do well in seasonally wet sites.
Native plants
On the flip side, Bruce Mero, a Master Gardener with the Cornell Cooperative Extension program, is an advocate for focusing exclusively on native plants, and believes that the way to plant locally to adjust to climate change is to use native plants in home landscapes.
“Natives in this geographic region have been adapting to the vagaries of changing climate since the end of the last ice age,” Mero said. “Natives have evolved to shrug-off droughts, floods, hot and cold shifts in temperatures, insect infestations, habitat loss, wildfires and most everything else our environment can throw at them. These plants have survived and thrived without human intervention. The ability of native plants to adapt to environmental change is a given. It has been occurring for millennia and will continue.”
More tips for resilient landscapes
The National Wildlife Foundation has a few additional tips:
- Incorporate diverse native species and reduce the threat of invasive species expansion. Native plants help to maintain important pollinator connections and ensure food sources for wildlife; nonnative plants can outcompete these important native species for habitat and food. Contact local or state native plant society, such as Cornell Cooperative Extension, to find out what plants are native to your area.
- Plant lots of trees to absorb carbon dioxide. Trees can absorb and store as much as a ton of carbon pollution (CO2) from the atmosphere.
- Homeowners can certify their backyard or neighborhood as a Certified Wildlife Habitat™ with the National Wildlife Federation. By certifying a backyard and encouraging neighbors to do the same, a neighborhood can become a Community Wildlife Habitat, which can help maintain or reconnect fragmented habitats and provide ways for wildlife to better cope with the impacts of climate change.
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