If you’re planning to plant or transplant a tree or shrub, it’s best to do it in the next month or so to avoid the heat and drought of summer.
“Give them time to get settled in while it’s still relatively cool,” said Sharon Yiesla, plant knowledge specialist at the Plant Clinic of The Morton Arboretum in Lisle.
Planting in summer has extra risks because the heat makes soil and plants dry out faster. As the temperature rises, water evaporates more quickly.
“New plants will always need watering on a regular basis to make sure the soil stays moist around their roots,” Yiesla said. The hotter it gets, the more often you need to check the soil moisture to see if it’s time to water around a new tree or shrub.
Plants are mostly water, and they need a steady, reliable water supply to survive. Between 80 and 90% of the weight of any green plant consists of the water that fills its cells. Even a mature tree, with its woody trunk and branches, is about 50% water.
In summer, plants cool themselves by allowing water to escape through tiny holes in their leaves, taking heat with it. The water that evaporates needs to be replaced for the plant to keep functioning.
The only way a plant can get water is to absorb it from the soil through its roots. New plants, including new trees and shrubs, don’t have a fully developed set of roots, so they have trouble taking in sufficient water. “They can’t tolerate even short periods of dry soil,” Yiesla said.
It’s possible to plant trees and shrubs in summer as long as you are prepared to give them extra attention, watering them whenever the top inch of soil is dry and watching them for signs of stress. Spreading a layer of mulch over the roots of a new plant — or any plant — also helps keep the soil from drying out.
For advice on how to plant or transplant a tree to give it the best chance of long-term survival, see mortonarb.org/planting-trees-and-shrubs. The most important thing is to dig a hole that is wide and not too deep, so that the plant doesn’t sit too deep in the soil.
Another option is to wait until fall to plant. Trees and shrubs planted between late August and the middle of October will have time to settle in and grow some new roots before the ground freezes. “That’s if you remember to water them,” Yiesla said.
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.