The size of a tree largely determines the amount of transplant shock it will experience, with larger trees generally experiencing more shock. This shock is mainly caused by root loss during transplanting - trees can lose 90 percent or more of their roots when they are dug - and results in smaller foliage for at least one growing season and reduced shoot length and diameter growth for several seasons. Recovery from transplant shock takes about one year for each inch of trunk diameter for an otherwise healthy tree. Minimize transplant shock by planting the smallest tree that accomplishes your purposes. Vandal-prone and high traffic areas may require larger trees to improve survival, though tall metal stakes also provide protection.
Landscape trees and shrubs can be obtained in four basic types or forms: bare-root, balled-and-burlapped, container-grown plants, and tree-spaded. Each type has its own advantages and disadvantages and none is ideal for all situations. With all four types be sure that you have an adequate root system - a good rule-of-thumb is that the root system, root ball, or container diameter or spread should be 10 inches to 12 inches for every inch of stem caliper (diameter at ground-line just above any basal swell). Therefore, a 3 inch caliper tree should have a 30 inch to 36 inch wide root ball as a minimum. Root ball depth is not as critical as width, but should be larger for larger trees.
- Bare-Root - Bare-root plants are dug from a nursery with no soil around the roots. Though bare-root seedlings may have a fairly complete root system, larger landscape-sized plants usually only have a few coarse, woody roots attached. These plants have the advantages of being inexpensive and light weight. However, extra care must be taken to keep their exposed roots moist. They also may be very difficult to find and generally are only available in the spring before bud burst. Bare-root deciduous trees should have a caliper smaller than 2 inches and bare-root evergreens should be very small (less than 2 feet tall). Bare-root trees should be planted only when they are dormant and spring planting is best.
- Balled and Burlapped - Balled and burlapped (B&B) plants are dug from the nursery with a ball of soil intact around their roots. The root ball is tightly wrapped with burlap held in place with twine, nails, and possibly a wire basket. Both fine and coarse roots are contained in the root ball so transplant shock is reduced. Rough handling, though, breaks roots and makes them lose soil contact, so handle these trees with care. B&B plants are much more expensive than bare-root trees and are much heavier but generally have a better chance of survival. Tilling the soil just outside the root ball 8 to 12 inches deep and several feet wide right after planting is one way to ensure good root growth.
- Container Plants - Trees are sometimes grown and sold in pots for convenience and to avoid root loss during transplanting. Containers are made in a variety of materials (plastic, compressed peat, etc.) and sizes. Container-grown trees are normally more expensive and heavier than bare-root but less than B&B. Round pots can cause roots to circle which may cause girdling roots later in a tree's life. Such roots should be cut or straightened at planting time. Container trees should be well-rooted without being root-bound - avoid buying bare-root trees that have recently been potted and are not well-rooted. Such trees may transplant well, but are more expensive than they are worth.
- Tree-Spaded - A tree spade, a large machine that cuts roots and soil so the root ball can be wrapped, is often used to dig B&B trees in the nursery. Some landscape contractors also move trees to the site and transplant them into a previously dug hole with the tree spade. These trees can be treated similarly to a B&B tree, but be sure that the gap between the root ball and the hole is closed so roots can grow out. Tilling around the root ball, as mentioned under B&B trees, is a good way to ensure good contact between the root ball and soil.
Trees can be obtained from nurseries and garden centers as bare-root stock, balled-and-burlapped stock, container-grown, or tree-spaded (not shown).
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