It has long been known that it is beneficial to plant trees and shrubs in fall. Warm soil stimulates roots to grow but cool above-ground temperatures mean the leaves are not demanding much moisture.
That said, when is it too late to plant in the fall? When does cold soil retard the establishment of woody plants?
Research at Cornell University concluded that the growth of new roots virtually ceases when the soil temperature becomes less than 40 degrees at six inches deep.
To determine how cold the soil has become in your area, consult the