Fall is a good time to plant trees and shrubs – the best time, in fact, for most of them. Whether purchased through the mail or locally, these plants are available in three ways:
Bare-root trees and shrubs are grown in the field, then dug up while they are leafless, which might be done in either fall or spring. Those dug in fall are sold immediately or are stored through winter with their roots packed in moist material. Root loss during digging is an obvious drawback to bare-root plants.
Although bare-root might seem like a brutal way to treat a tree or shrub, the plants handle the move well as long as their roots are kept moist prior to planting.
Bare-root trees and shrubs should not be dug until they have lost all, or nearly all, of their leaves in the fall. And their roots must be cozied into the ground before shoots start growing, which is not a problem in the fall. This highlights one advantage of fall planting: There's no danger of shoots growing prematurely, because shoot buds stay dormant until they have experienced a winter's worth of cold.
The biggest advantage of bare-root plants is that they are easily and relatively cheaply shipped all over the country, giving you the widest possible selection in varieties. What's more, because you can see the roots, you can easily assess their condition.
Balled and burlapped trees and shrubs are also grown in the field, but they are dug up with a ball of soil that is then snuggled into a wrapping of burlap.
Because clay soils hold together better than lighter soils, balled and burlapped plants are usually grown in clay soils. But clay soils also are heaviest, so such plants are heavy. Weight and the need for extra care to avoid breaking up the root ball make mail-order shipping of balled and burlapped plants unfeasible. Root loss can be extensive when balled and burlapped trees and shrubs are dug, and plant selection is limited.
Increasingly, both local and mail-order nurseries are selling trees and shrubs as container-grown. These nursery plants spent their lives in pots. The potting mix is lighter than field soil, so such plants can be economically shipped through the mail. Container-grown plants can be planted any time of year as long as you can dig a hole and water them as needed.
Ideally, a container-grown plant spends long enough in the container so that its roots just fill it.
Watch out, though: Some garden centers and nurseries buy bare-root trees and shrubs, and then pot them up for quick sale as container plants. And equally bad, plants that are truly container-grown are often left too long in their containers. Once the roots start growing round and round in the pot, they can actually choke the plant, a condition that continues to develop even after the plant is set in the ground.
If possible, check the quality of a container-grown plant by sliding it out of its container to make sure it's not rootbound, with roots that are very thick and tangled. The top growth of a well-proportioned potted tree or shrub should be no higher than two to three times the depth of the container to ensure a good ratio of roots to stems.
Small is better
Whether you're buying bare-root, balled and burlapped or containerized trees and shrubs, restrain yourself from buying the largest possible plant. In the case of the first two kinds of nursery plants, small plants suffer less root loss in transplanting.
With smaller plants of any of the three kinds of nursery plants, less water is needed after planting, and new roots more quickly explore surrounding soil to make the plant self-sufficient. Not too long after transplanting, growth of an initially smaller plant frequently overtakes that of an initially larger one.
– Lee Reich, Associated Press