A properly planted tree or shrub will be more tolerant of adverse conditions and require much less management than one planted incorrectly. Proper planting technique has an impact on water quality, because it minimizes water, fertilizer and pesticide use. Factors to consider when making decisions on planting techniques include the plant's nursery history (container, field, or greenhouse), drainage requirements, the soil type and drainage characteristics, and the availability of irrigation water. The plant should be specifically appropriate to the site, or the site should be amended to specifically fit the plant.
Horticulture researchers have estimated that 75 percent of the roots may be lost when digging field-grown nursery stock. Cultural practices performed by nurserymen, such as root pruning, irrigation, fertilization, root-ball configuration, and digging techniques, influence the percentage of harvested roots.
Water stress, caused by the removal of most of the water-absorbing roots, is the primary cause of transplant failure. Most water-absorption capability within a transplanted root-ball results from very small roots. These fragile roots are the first to suffer from excess water loss in newly transplanted landscape plants. Before planting woody ornamentals, steps should be taken to make certain that the soil is well-drained and well-prepared. This encourages rapid plant establishment and optimum growth.
Nursery Stock Options
North Carolina nurseries can provide plants grown and packaged in a variety of ways: bare-root, balled-and-burlapped, fabric container and plastic container. Some large landscape trees are mechanically dug with a tree-spade and placed in wire baskets. Each of these harvesting and growing techniques is acceptable but requires a specific planting and management technique.
Container-grown ornamentals can be transplanted successfully throughout the year with little transplant shock. However, balled-and-burlapped ornamentals are more likely to undergo more transplant shock because a large portion of their root system has been destroyed in the digging process. The best time to transplant container-grown ornamentals is from mid to late fall to early spring. Plants will require extra care when transplanted during the hot summer months. Many ornamental trees and shrubs are now being produced in fabric bags in the field. Current Extension Service recommendations for plants produced in fabric bags is to handle them much like balled-and-burlapped plants, but remove the fabric from the root ball when transplanting. Bare-rooted ornamentals such as packaged roses are dug and transplanted during the dormant winter season. When transplanting ornamentals from one location to another in the landscape, it is best to wait until the plants are dormant to transplant them for best results.
Bare Root Plants
Advantages of planting bare-root plants are mostly economic. Plants are less expensive to produce because of the ease of harvesting, storing and shipping. Many species respond well to bare-root harvesting. A greater portion and longer roots are retained after harvesting and roots are easily inspected at planting time. Damaged roots can be trimmed and girdling roots can be removed before planting. Bare-root plants should be planted while they are completely dormant. Landscape-sized bare-root trees usually require staking.
Balled-and-Burlapped Plants
Larger landscape plants are traditionally harvested as "balled- and-burlapped"(B&B). A major advantage of B&B plants is that soil types can be matched, thereby reducing any interface problems that might inhibit water movement between the root ball and surrounding soil of the landscape site. There is an acceptable, standardized formula for sizing root balls known as the American Standard for Nursery Stock.
B&B material often has a large portion of the roots severed at harvest time. The number of roots harvested depends upon soil type, irrigation practices and root pruning during the production period. Plants moved B&B are subject to seasonal constraints. The most favorable seasons are when transpiration demand is low and root generation potential is high, such as in fall, winter and early spring. With the much-reduced root system, water is a critical element in the successful transplanting of B&B material.
Container-Grown Plants
The advantage of using plants grown in containers is that 100 percent of the roots are in the container. Thus, if given adequate follow-up care, the plant goes through limited transplant shock. Container-grown plants can be planted into the landscape year-round. Plants produced in containers in a soilless medium (usually bark and sand) are much lighter than B&B material.
The main disadvantage of container-grown plants is the possibility of deformed roots. "Rootbound" plants have roots circling inside the container. The entangled roots are a physical barrier to future root growth and development. If this condition is not corrected at planting time, the plant may experience slow growth and establishment because of the girdled roots. Some form of root mass disturbance is recommended before planting.
A relatively new production system is the use of fabric containers or bags. Plants are grown in the bags and placed in the ground with a soil backfill. The advantage to this production technique is purported to be a means of harvesting a greater number of roots while using field production practices. The fabric must be removed at transplanting time. This can be somewhat difficult when the roots have become attached to the walls of the bag or if roots have escaped through the fabric.
Smaller plants survive better and establish faster than large plants and are more economical. However, demand for large, landscape-size trees has certainly increased over the last decade, due to the desire for instant landscapes. With large mechanical digging equipment, 6-to 8-inch diameter trees can be moved. Large diameter trees are often transplanted for instantaneous effect, but post-transplant stress and costs increase with the size of the tree.
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