Gardener: Transplant trees and shrubs in fall for best results

Throughout the year, one of the most common questions I get relates to the best time to plant or transplant trees and shrubs. My quick answer is that as long as the ground isn't frozen, you can plant any time, although you decrease your chances of success substantially if you don't do it in autumn; no matter where you live, fall is the very best time.

Even in the warmest regions, the cooler air and warm soil temperatures of fall make the best combination for establishment. Cooler air is kinder to plant foliage, and reduces the chances of an energy-zapping chain reaction throughout the rest of the plant. This is especially true for the ones that have just lost a major portion of their roots from being dug up. In addition, soil temperatures are still warm, which creates an excellent environment for the production of new root growth.

Another benefit to fall transplanting is that many plants and trees are entering a period of dormancy. With no need to allocate resources into foliage, plants are now transferring all their energy into roots and storing nutrients and resources for the cool months ahead. By spring, the result should be a well-established root system and plants that are better equipped to handle the upcoming demands of spring and summer.

Here are a few additional tips to ensure the success of all your fall transplants:

When preparing any hole for an incoming shrub or tree, make the hole two to three times wider than the current root ball, but don't make it any deeper than the plant was growing in its previous environment. An even better guide with trees is to look for the flare of the trunk near the soil level. In the planting, don't place the tree to a point where any part of that flare is ultimately covered with soil. I provide this added bit of guidance because, unfortunately, even nurseries sometimes put plants too deep in the containers. There have been many times where I've actually had to pull away soil to get back to the base of the trunk flare.

I go one step further by placing transplants in their new environment with up to 1/3 of the root ball higher than the surrounding soil level. I then taper soil up to cover all the roots and add a generous layer of mulch above that. Newly disturbed soil has a tendency to settle, and plants growing below grade can easily succumb to root rot or disease. In my book it's always better to plant a tree or shrub slightly high and allow the area to drain than for a plant to sit in a bowl and collect excess water.