When you shop for trees, you will find them offered for sale as bare-root, containerized, balled and burlapped (B&B), and tree spaded.
You will generally receive mail order trees, shrubs, and fruit plants as bare-root. There are restrictions on shipping soil across state lines, plus there is additional expense in shipping some weight of soil. Some governmental agencies sell bare-root trees and shrubs for windbreaks and other conservation purposes. These are generally available in large lots of plants. Some garden centers may stock a limited supply of bare-root trees in early spring. You can ask them to special order bare-root stock for you, but you’ll probably need to place an order in late fall.
Containerized trees and shrubs have been field-grown in a wholesale nursery for several years. In fall, they are dug, then stored bare-root at high humidity at near-freezing temperatures over the winter. In spring, they are shipped to garden centers and retail nurseries and potted up. The caveat here is that containerized trees and shrubs may be planted too deeply in the container, so the conventional wisdom of planting the tree or shrub no deeper than the depth at which it was growing in the pot does not hold. Before final placement, you will need to check the depth. The first lateral root (also called first order root) should be no more than 1/4-inch below the soil surface.
Balled and burlapped trees and shrubs are available each spring. By law, root-balls must be covered with wood chips or another moisture retentive medium so the root-balls don’t dry out. Nurseries routinely root prune their young trees in the field to encourage formation of a more compact, fibrous root-ball. These trees retain a larger percentage of their original roots when dug than “volunteer” trees dug from the wild or established plantings that are moved later. These B&B plants are tree-spaded out of the ground and placed in burlap-lined wire baskets. The basket is secured by cord wrapped around the trunk of the young tree. The rope, part of the burlap and basket, should be removed at final planting.
Tree-spaded trees, often advertised as “instant” landscaping, are trees that are dug and immediately moved to the new planting site. However, because of their increased size, they take longer to become re-established in their new home. Research has shown that smaller trees, such as containerized trees, will establish more quickly than larger tree-spaded trees. The smaller trees can catch up in size to larger trees.
Plants have a layer of moisture surrounding their leaves. When this mist is lost to air movement, stomata on the leaves open and pull water from the roots up to replace the moisture lost. Imagine how quickly a tree in full leaf riding in the back of a truck loses moisture! When transporting trees, it is imperative that plants in leaf be covered by a tarp or otherwise covered to prevent the moisture from being whisked away.
For additional information on shopping for woody plants, review: