Why fall is the best time to plant trees

Fall – not spring – is the ideal time to plant trees and other woody plants, said Nancy Kuhajda, a University of Illinois Extension horticulture educator serving Grundy, Kankakee and Will counties.

Fall is the period when leaves start to change colors and drop from the trees, she said. That can be meteorological fall or astronomical fall.

“It’s when plants start to shut down for the year,” Kuhajda said.

So, if you missed spring planting, don’t fret. Here are three reasons why it’s better to wait:

Trees need a period of establishment

The University of Illinois Extension said “all newly planted trees are in a state of shock until they become ‘established’ at their new planting site,” which can persist for several years.

Even if spring weather favors tree planting, summer might quickly bring high temperatures and drought. This can stress a newly planted tree trying to establish a root system, Kuhajda said.

With fall, the odds of having six to eight weeks of cooling temperatures are good, she said.

As long as the hole is already dug, it’s not too late. The roots will continue to grow even after the top has gone dormant.”

—  Nancy Kuhajda, Illinois Extension horticulture educator serving Grundy, Kankakee and Will counties

The only trees one should not plant in the fall are fruit-bearing trees, Kuhajda said. These trees do best with spring planting since they need more time to establish themselves, she said.

“It’s better to plant those in the spring,” Kuhajda said. “But you could easily plant a crabapple or ornamental fruit tree.”

It saves money

Local nurseries and big-box stores often offer sales in the fall so businesses don’t have to overwinter their trees, Kuhajda said.

“Many of them have great deals going on right now,” Kuhajda said. “These are perfectly healthy plants.”

The tree has a chance to prove itself

Kuhajda said some big-box stores give a year’s guarantee to see “if the tree makes it or needs to be replaced.”

By planting in the fall, trees get a full growing season, she said. This gives tree owners until the following fall to receive the year guarantee, Kuhajda said.

She said it’s important to water a tree at the time of planting and then until the ground is solidly frozen.

“An inch of water a week is ideal,” Kuhajda said.

How late is too late to plant?

It’s never too late to plant trees and shrubs as long as the hole is pre-dug, Kuhajda said.

The University of Illinois Extension recommends “digging the hole twice to three times as wide as the root ball but no deeper, loosening the root ball and spreading out roots.”

“I sometimes get calls when people are horrified at seeing landscapers planting barren trees into frozen ground,” Kuhajda said. “Personally, I get a lot of roses shipped in November, and sometimes the ground is frozen solid. But as long as the hole is already dug, it’s not too late. The roots will continue to grow even after the top has gone dormant.”

Roots will continue to get nutrients until the ground solidly freezes, which might not happen in this area until February, Kuhajda said. Trees that are planted in the fall benefit from this extra establishment time before dealing with the stress of hot weather, she said.

Actually, people still can plant perennials in the fall, too, Kuhajda said. But don’t plant annuals in the fall.

“Their year has already ended,” she said.

For more information, contact Kuhajda at 815-727 9296 or kuhajda@illinois.edu.