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 2004, https://www.anla.org/publications/index.cfm)
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.
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”).
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”)
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.
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.
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.
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.
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.
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.
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.
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.
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
