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Guidelines for Growing, Installing and Maintaining Healthy Trees

Prepared by the Illinois Tree Specification Review Committee

Nursery Propagation, Growing, Harvesting & Handling:

Installation of the "Package"
(click thumbnails for full image)

It takes only a short time to plant a tree, but how it is done can have a lasting influence. Mistakes made when planting tress are usually impossible to correct later. Shortcutting the planting process can cause the tree to fail after a short time, or to struggle for many years and never reach its full potential as a healthy vigorous addition to the landscape. Attention to detail taken at planting time will pay dividends for years.

Checking Structural Root Location
Removing Non-Biodegradable Materials
Pruning
Planting Pit Depth and Width
Placement of Structural Roots in Relation to Grade
Backfilling the Planting Hole
Watering
Trunk Protection
Staking
Mulching
Fertilization

Checking Structural Root Location
As a general rule for young nursery-grown trees, there should be two or more structural roots within 1-3 inches of the soil surface, when measured 3-4 inches away from the trunk. The structural roots should be distributed radially in all directions. The size and number will vary with species. If the roots are deeper than this, consider rejecting the stock, as the root ball may be undersized. (See American Standard for Nursery Stock)

 234rulenoback

The best time to determine root depth is while tagging trees, before they are dug. It can also be done after the trees are dug. Checking both in the nursery, and rechecking just before planting, may be the best way to be absolutely sure that the roots are not too deep in the root ball. Checking for root depth can be done several ways. A gap around the base of the trunk is a sign that the roots are too deep. An inexpensive surveyor's chaining pin, or a stiff piece of wire, can be used to probe for roots in the field, or in the root ball. The severed ends of the structural roots can sometimes be detected through the burlap on the sides of the root ball. Carefully removing soil from around the base of the trunk with a hand trowel is also acceptable, but difficult to do after the root ball has been wrapped.

gap

excavation

Removing Non-Biodegradable Materials
Materials used to cover and support the root ball during transport and storage can injure trees if left in place after planting. If root ball has been reburlapped, burlap on the outside of basket should be removed after the root ball is placed in planting hole. Remove all basket wires down to 4-6 inches below the root ball shoulder to eliminate the wires most likely to make contact with the structural roots (High profile package). After removal of basket top horizontal ring(s) and loops, twine can be retied over top of root ball to stabilize trunk through first year (high profile package – Removal of top ring(s), loops and retying).

 high profile wire

Low-profile baskets are designed so that there is no wire that needs to be removed. It is not necessary to remove the loops, even if they are less than 4-6 inches below the root ball shoulder. Chances of roots growing through them are low. (Low profile package)

 low no wire

If all burlap and twine are not removed from the top of the root ball,and down the side to 4-6 inches below the shoulder at the time of planting, each root ball should be inspected within a year to confirm that the burlap and twine have rotted away and are not damaging the tree s root system.

Pruning
If pruning was done correctly during production in the nursery, the tree should require very little pruning when planting, except for removing broken twigs. It is best to not make large pruning wounds on the stem. Proper pruning cuts just outside the branch collar are imperative.

 branch collar

Planting Pit Depth and Width
The planting hole volume should be large enough for rapid initial root development during the first year and to encourage root spread beyond the planting hole. The planting hole should be slightly shallower than the root ball to anticipate pancaking of the root ball. Two inches high is adequate for a 2-3 inch caliper tree. Up to 4 inches high may be needed for larger root balls. The root ball should be placed on stable subgrade to minimize settling.

 2 inches above grade

On sites with poor quality (compacted, clayey or poorly drained) soil, the planting hole should be at least two times the width of the root ball diameter. If the roots are unable to grow into the compacted subsoil, a hole with sloped sides will allow them to gradually grow back up toward the better quality surrounding surface soils and continue to spread beyond the planting hole. On sites with high quality soil, the planting hole needs to be only wide enough to facilitate planting.

 two times

If the sides of the hole are glazed or dried, use a hand tool to break up surfaces before planting It is not possible to dig a wide hole when installing trees with a tree spade. After planting, the soil around the root ball can be deeply cultivated to eliminate air pockets and provide a favorable environment for new root growth, similar to a wide planting hole

Placement of Structural Roots in Relation to Grade
If structural roots are found at the correct depth, plant with the top of the root ball slightly above grade (Planting pit depth and width). If the structural roots are slightly deep in the root ball, the planting hole should be shallower to account for it. It is most important to get the structural roots at the correct depth. Leave the extra soil intact, at least until it is placed in the planting hole and backfilled.

 plant high

In some situations it may be preferable to leave the extra soil above grade rather than remove it, and risk cold or sunscald damage. If the extra soil over the structural roots is filled with fibrous roots, removing them suddenly could cause extra stress. The extra soil should gradually erode away. Mulch can be used to cover the protruding root ball and make a more gradual slope.

 plant too high

Backfilling the Planting Hole
Compact some of the excavated soil around the base of root ball to stabilize it. The rest of the soil should be tamped only lightly, or left to settle on its own. Watering will assist in settling the soil naturally. Excessive tamping can compact soil and slow water penetration and root growth.

 planting mix

Backfill soil amendments may be desired on sites with poor quality soil to improve soil structure, water-holding capacity, or drainage. On sites with high quality soil, the backfill does not require amending.

Watering
In the first year or two, it is important to keep the root ball moist, but not over-watered. The root ball soil is the major source of water for the tree until the root system redevelops. During this time, monitor the moisture in the root ball. Surrounding soils where there are few roots absorbing moisture often stay moist, as the root ball is quickly drying out.

 waterroot

Use of tree watering bags is gaining popularity. They deliver water to the right place. We know very little about heat buildup on the trunk under the empty bag. An empty bag may also deflect rainwater away from the base of the tree.

 water bag

Throughout the warm, summer weather, the tree will probably need water about twice each week. Approximately 5-10 gallons of water is sufficient to moisten a 20-inch diameter root ball. A 40-inch diameter root ball has more than twice the volume and would require 35-45 gallons For complete planting diagrams see

Trunk Protection
Plastic guards can help to protect trunks from mowers, weed whips and other mechanical injuries. If used, they must be removed before the trunk grows large enough to be damaged. Where sunscald or frost cracks are common, trunks of thin- and/or smooth-barked trees are sometimes wrapped to prevent injury from winter sun. However, the preferred wraps are light in color, porous to water and biodegradable, and should be removed in the spring, no later than May 15 in the Chicago area.

 protect base

Staking
Staking, guying, or bracing refer to mechanically supporting the trunk of a planted tree to keep it in an upright position. Staking is not usually necessary for properly handled and planted B&B stock. If the root ball is in good condition, and has been stabilized by compacting soil around the base, the tree is not likely to lean or shift. Many contractors feel that leaving the burlap and twine over the root ball for the first year helps to hold the root ball together and keep the tree straight. There may be a few exceptions where staking is needed, such as very windy sites, or sandy root balls.

 no stakes

If a tree must be staked, be sure stakes and guys do not create a hazard for people. Guying material should be wide, smooth, nonabrasive, flexible, and if possible, photodegradable. To prevent injury to the bark, the guying should be examined at least once during the growing season and adjusted if necessary. Supports should be removed after one year to avoid trunk girdling.

Mulching
Apply mulch over the entire planting hole to conserve soil moisture. The mulch layer should be 1-3 inches deep after settling, depending on the size of the tree. Mulch should not be allowed to cover the base of the trunk.

 mulch

Mulch is often incorrectly piled up to 1 ft deep in a small circle only about 3 ft wide around the tree. This is of little benefit to the roots, sheds water, can be potentially damaging to the trunk. It is aesthetically unpleasing, and sometimes called “volcano mulch”.

 incorrect mulch

Sometimes the ‘volcano mulch' can be covering up a bad planting job. It can be hiding excess soil from the planting hole that was piled around the base of the tree rather than being hauled away.

 volcano mulch

Fertilization
Drought stress limits the growth of newly planted trees more than any other factor. Until the root system can grow and absorb more water, adding fertilizer to the soil is likely to be ineffective.