Trees and shrubs add beauty and value to a home’s landscape. But as few as 50% of planted trees do not survive beyond one or two years. Why? Improper installation is the leading cause of failure of newly planted trees. You can grow trees successfully if you are aware of a few important planting guidelines.
Planting the biggest tree you can afford is not always the best option. Though it is true 2” to 4” caliper trees give an instantly-landscaped look to homes, these trees are more prone to transplant shock and water stress. Transplant shock occurs from the loss of root system when the tree is dug from the nursery. As much as 95% of the plant’s roots may be removed during the digging process. This means fewer roots are available to provide water to the many branches and leaves. Symptoms range from scorch on the edges of leaves, dieback in the crown, increased vulnerability to diseases, insects, and drought, or tree death. Transplant shock, more or less, continues until the tree canopy and tree roots come into balance. For comparison, a 1” caliper tree planted with 5% of its root mass, provided good care, can recover 100% of its roots by the end of one year. A 4” caliper tree planted with 5% of its root mass, will take five years to recover 100% of its root mass. During this time the smaller caliper tree may easily catch up in size to the larger tree.
Planting too deeply can kill trees. This problem may occur from three causes. First, overambitious hole diggers can easily dig the planting hole too deep for the root ball. Backfill placed in the bottom of the hole that is not recompacted will allow the root ball to sink as the soil settles. Avoid this situation by measuring the height of your root ball and leaving about 10% of the ball aboveground. Another common mistake is excessive mulching. Excessive mulch reduces the amount of oxygen reaching the roots, causing them to grow into the mulch. During a drought the mulch will dry out as will the roots, thus causing root loss. Never apply more than 2 to 3 inches of mulch. Finally, sometimes trees may be shipped from the nursery already at a disadvantage. Container stock that has been transplanted into larger pots could have its roots buried in the process. Balled and burlapped trees may have extra soil on the top of the ball due to cultivation and digging. As a result, the roots become too deep in the ball or container. Inspect trees at the time of purchase to see if the root flair (the place where the trunk becomes the roots) is near the surface. Ones that are 2 or more inches below the surface should be avoided or at the very least remove the soil until you can see the root flair when planting. Remember to use only the existing soil on site when filling in your planting hole, no amendments should be added.
It’s okay to loosen or even cut the roots. When planting container-grown trees be sure to remove the container and inspect for circling roots. You may be able to tease these roots loose from the media and spread them out in the planting hole. If a plant is severely pot-bound, use a knife or pruners to make vertical slices through the roots in several places to divide compacted roots. Leaving circling roots will eventually lead to girdling of other roots or the tree trunk itself. Girdling restricts the movement of water to the tree’s canopy and can lead to decline. Girdling can also occur on balled-and-burlapped trees. Natural burlap is bio-degradable and needs only to be removed from the top portion of the root ball, but synthetic burlap will not decompose and can girdle roots. If a wire basket is holding together natural burlap, remove it if possible, if not cut and fold down the top half of the basket. If your planting hole is too small, don’t break or bend roots to make them fit. Take the time and enlarge your planting hole. The hole should be 2 to 3 times as wide as the root ball at the top of the hole sloping inward to the width of the root ball at the base. Be sure to remove tags, wires, or ropes from the stems or trunk of plants.
Submitted by Kelly Jackson, Agent for Horticulture, Christian Co. Cooperative Extension Service