The proper installation of plants in the landscape involves much more than just digging holes and setting plants in them. The existing soil is often compacted and poorly drained. Tilling or digging to improve aeration and drainage is essential for satisfactory plant growth.

The current trend is to plant trees and shrubs in large beds. Preparation of an entire bed is preferred over preparing individual holes since the roots will have a larger area to grow before they encounter native soil that might be compacted and poorly aerated. To achieve a 25 percent increase in organic matter, incorporate 3 inches of organic matter, such as pine bark mulch or compost, into the top 12 inches of soil. The organic matter used should be composted or aged. Incorporating uncomposted organic matter can create nutrient deficiency problems. Adding organic matter when preparing individual holes is not recommended.

Plants can be purchased as bare-root, ball and burlapped (B&B), or as container-grown plants. Planting procedure varies somewhat with each type.

Planting container-grown plants
Container-grown plants have become the most popular method of growing plants for sale by the nursery industry. In theory, container-grown plants can be transplanted year round, however, extra attention to watering must be made when transplanting in late spring or summer. Late fall and early spring are considered ideal planting times because roots will have more time to grow into the surrounding soil before the stress due to new foliage growth and high temperatures occurs.

The planting depth should be such that the plant is exactly the same depth after transplanting as it was in the container. Ideally, the hole should not be dug any deeper than the root ball. The loosened soil below the root ball can settle resulting in the plant being planted too deep. If you dig too deep, firm the bottom of the hole to reduce settling. Since most new roots will grow horizontally from the side of the root ball, soil firmed at the bottom of the hole will not substantially affect root growth. In most compacted urban soils, root growth from the bottom of the root ball will be limited by inadequate aeration and possibly excessive moisture. In some cases the roots in the lower portion of the root ball die after transplanting. Efforts to improve the soil should be directed near the soil surface by preparing the entire bed or digging wide individual holes.

Widening the planting hole is an ideal way to enhance plant growth. A planting hole that is three times the width of the root ball with the sides of the hole sloping towards the bottom is ideal in most situations. When digging in heavy soil the sides can become slick especially if the soil is somewhat wet. Slick sides can act as a physical barrier to root growth and moisture movement. Use a shovel to make the sides of the hole rough and irregular.

Always water plants thoroughly before transplanting. Remove the plant from the container by turning the plant upside down and giving the top edge of the container a sharp rap. Catch the root ball in your hands as it slips from the container. If plants have become overgrown in the container and the root mass is growing in a tight, compact circle the roots should be loosened before planting. If the roots are only slightly encircled you can loosen and spread them out by hand. Many gardeners cut the outer roots with a sharp knife by making vertical cuts approximately 2 inches into the root ball on two to four sides of the root ball. Some gardeners split the lower half of the root ball and spread the roots horizontally. This practice raises the lower roots closer to the soil surface. Plants such as azaleas, rhododendrons, and daphne that are especially prove to developing root rot in poorly drained sites could benefit from this butterflying practice. After the roots have been loosened or cut, carefully place the plant in the hole. Always pick the plant up by the root ball never by the trunk or stem (can cause damage to fine root hairs).

Soil that was removed from the hole should be used to refill the hole. Traditionally, the recommendation was to incorporate organic matter into the backfill (soil used to fill a planting hole). Some gardeners took the practice further and completely replaced the removed soil with purchased topsoil. Research has shown neither practice helps plants grow and in some cases can be detrimental. When water enters soil with one type of texture and later comes in contact with soil that has a very different texture water movement (drainage) is impeded. Excessive water can accumulate in the bottom of the hole which can lead to root suffocation or root rot development. Some researchers report that amended backfill can cause roots to remain in the planting hole instead of growing into the surrounding soil (roots will grow in the area of least resistance and greatest soil aeration). The primary reason for digging a wide hole is to improve soil aeration and to reduce compaction.

Lime should be mixed with the backfill, if needed, based on a soil test. Fertilizer should not be added at planting since it can burn the roots. An exception would be the application of phosphorus which moves very slowly, or not at all, in the soil and plays a key role in root formation. It will not burn the roots. Liquid fertilizers are some times applied after planting, but their benefit has not been proven.

Fill in around the plant with soil until the hole is one-third full. Firm the soil around the root ball, however, be sure not to use excessive force since soil compaction should be avoided. Loosen and break up any clods of soil before backfilling. Clods can create air pockets around the root ball. Before finishing the filling process, make certain the plant is straight and at the proper planting depth. It is important when planting (particularly container-grown material) to avoid covering the top of the root ball with more than 1/2 to 1 inch of fine soil. Ideally it should be level with the soil surface. Otherwise, water can be diverted sideways through the native soil and not soak down into the root ball where it is needed.

After a tree or shrub has been planted, construct a ring of soil 2 to 3 inches high to form a water basin at the outside edge of the hole (plants in beds probably will not require a water basin). This permits water to go into the root zone rather than running off the surface. Water the plant to eliminate air pockets around roots. The water basin does not need to be a permanent fixture and can be removed after the plants become established. Apply a 3-inch layer of mulch over the planting hole. The mulch will help maintain moisture and reduce fluctuations in soil temperature. The mulched area should be expanded as the plant grows.

Planting bare-root plants
Bare-root plants are usually the most economical form of plants but require more care after planting. These plants were grown in a field nursery and dug during the dormant season. Soil was removed from their roots before they were put into cold, moist storage. At shipping, the roots are covered with damp peat moss or sawdust, wrapped with plastic, and placed in the mail. Few evergreen plants are sold bare-root; most are deciduous trees or shrubs. Plants with a long tap root, such as nut trees and some fruit and shade trees, are often sold bare-root because they are not adapted to balling and burlapping or container production. Mail-order companies often sell bare-root plants because it is more economical to ship plants without soil. Some retailers carry bare-root plants packaged in cardboard containers with roots wrapped in damp sphagnum. Occasionally bare-root plants are potted into containers and misleadingly offered as container-grown plants.

Bare-root plants should be planted while they are dormant. Fall planting is well-suited for these plants. However, many mail-order companies do not ship until spring.

When plants arrive in the mail check them for moisture. Never let the roots dry out. Keep the roots wrapped in wet paper or sphagnum moss and covered with plastic until you are ready to plant. Keep the plants in a location with cool but above freezing temperatures; roots can be easily damaged by freezing temperatures.

Before planting the roots should be soaked in water for at least an hour but not more than 24 hours. Longer soaking can drown the roots from lack of adequate oxygen. Prune off any broken or damaged roots before planting. Never leave the root exposed to wind and sun even during the planting process; keep the roots protected by wrapping in moist burlap or place them in a bucket of water. Build a mound of soil in the center of the planting hole and spread the roots around it. With bare-root plants, the soil should be worked gently in and around the roots while the plant is being supported to ensure good soil-root contact. Water to eliminate air pockets. Bare-root plants may need some light pruning after planting.

Planting balled and burlapped plants
Balled and burlapped plants have been grown in field nursery rows, dug with soil intact, wrapped with burlap, and tied with twine. The size of the root ball will vary with plant size. The diameter of the root ball should be 10 to 12 times the diameter of the tree trunk measured 6 inches off the ground. Most of the plants sold as balled and burlapped (B&B) plants are large, evergreen plants and deciduous trees. They transplant best during late fall and early winter but can be successfully done in the spring. Some field-grown plants are being produced in fabric bags. They are handled essentially the same as B&B plants except the fabric bag should be removed at planting.

Many B&B plants are root pruned in the nursery so the root system will be more compact and fibrous. Even with the best nursery efforts, many (up to 95 percent) of the roots are lost in the digging process. The remaining small portion of the plant’s former root system can have difficulty absorbing enough water to meet the plants needs.

When selecting a B&B plant, be sure the ball is sound and hasn’t been broken. Avoid plants that feel loose in the soil ball. B&B material must be handled carefully. On most species if the soil ball is broken, many of the small roots will be severed from the trunk and the plant will die. Always pick the plant up by the soil ball --- never by the trunk or stem. Be sure the soil ball does not dry out or is exposed to hot summer or freezing winter temperatures for an extended period of time before planting.

The planting procedure is essentially the same as for container-grown plants. The burlap should be left on the root ball unless it was made from a synthetic material or has been treated with a chemical preservative. To determine the difference between natural and synthetic material hold a match to a small portion of the burlap. Natural material will burn while synthetic will melt. Untreated natural burlap has a tan color and is biodegradable. The burlap on top of the root ball should be cut, rolled back, and covered with soil. If part of the burlap is exposed above the soil line it can act as a wick that will remove moisture from the root ball.

After positioning the plant in the hole, remove any straps, ties, strings, or wires secured aroun the root ball. Wire baskets are often used to reinforce the root ball during shipping. Experts disagree on possible harm that the wires might cause if left in the planting hole. It might be safer to cut and remove the top portion of the basket. Removing the entire wire basket can cause the root ball to be damaged. B&B plants usually need little pruning at planting but may need careful watering during the summer.

Prepared by: Erv Evans, Consumer Horticulturist, NC State University

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