Plant Care During the Establishment Period
A tree is considered established once its shoots and trunk(s) are again growing at the rate they previously grew at the nursery. The time required for a tree to establish itself varies primarily based on the diameter of the trunk and the growing zone in which it is planted though other factors such as soil structure can also affect the time required. In general, container-grown trees require more time than field grown and hardened off trees.
After planting, the growth of a tree’s shoots and trunks slows somewhat while the plant redirects resources to generating new roots. They require frequent irrigation at this point. As roots begin to grow into the surrounding soil, irrigation will be required less and less frequent. Once the tree returns to its normal growth rate, it will have developed a substantial enough root system that it no longer requires supplemental irrigation.
Other considerations during the establishment period include mulching to help hold in moisture and regulate temperature of the soil. Some planting sites with frequently strong winds may require that the tree be staked until it is established. You may also need to fertilize and prune differently during the establishment period.
Watering Plants During the Establishment Period
The period between when a tree is planted and when it is fully established is a vulnerable period for the tree and sometimes results in its death. Frequently, those deaths are due to improper watering during the first few months following planting. Often, trees in well-drained soil are underwatered, while those in poorly drained soil are overwatered. If a tree develops tip dieback as a result of being underwatered during dry weather and then wet weather returns, the tree sometimes develops new shoots from the living tissue behind the dead tip that become dominant and compete with the trunk. This can result in a poorly structured tree with several trunks.
To avoid such problems, you should become familiar with the properties of the planting bed. The goal should be to keep the root ball at a constant moisture level while not saturating it or the soil around and beneath it.
If a tree is planted in well-drained soil, its root ball where all the roots are located initially should be irrigated daily for at least a month. This will keep the root ball at a relatively constant moisture level promoting faster and more extensive root growth. If the surrounding soil is dry, then it can be watered as well. The faster that you can get the tree’s root system to grow, the faster it will become established and resistant to drought.
While attempting to keep the root ball of newly planted trees moist, an existing irrigation system designed for your lawn or existing flower beds containing established plants will typically overwater the surrounding landscape before the root ball gets enough moisture. For this reason, you may need to water the newly planted trees by hand or come up with a temporary irrigation solution such as soaker lines, driplines with multiple emitters, or drip irrigation bags around the trunk to direct the water to root ball, not the surrounding soil where the roots have not yet grown.
You should continue to irrigate the tree regularly for the next several months, gradually expanding the irrigation area beyond the root ball to account for the expanding root system. If it rains, you should usually continue to irrigate as scheduled unless you receive more than an inch of rainfall in a week.
Trees planted in poorly drained soils should be planted with the top of their root ball two to four inches above the soil surface as previously mentioned which will keep the top of the root ball out of any standing water the might accumulate in the planting soil. Water from an irrigation system designed for turf or established plants can collect in the looser backfill soil around a newly planted tree’s root ball and drown its roots. For this reason, you may consider redirecting the existing sprinkler and sprayer heads around the tree so that they do not water the tree and install a temporary irrigation solution like those mentioned for trees planted in well-drained soil. Of course, this might mean some of the turf may get under-watered. Once established, the tree should be able to survive on moisture from normal rainfall.
Staking Trees During the Establishment Period
If possible, you should avoid staking newly planted trees. But if your tree requires staking, it should only remain staked for a short period of time until it becomes established. There are a few important tips to follow when staking a tree or shrub to reduce the chances of damaging it.
Trees that are more than 4 feet tall will frequently need to be staked when they are first planted to hold them in place until the roots can establish themselves. The stakes can be metal or wooden and should be placed around the perimeter of the root ball taking care not to drive them “through” the root ball. The tree should be secured to the stakes with heavy wire run around the trunk just above the lowest scaffold branch if possible. Cut a section of garden hose and run the wire through it where the wire loops around the tree trunk to protect the tree. The guy wires should be taut enough to keep the tree from tipping over but still allow the tree some movement as slight movement in the wind promotes a better root system and stronger trunk.
Once the tree is established, the stakes and guy wires should be removed. If you plant a tree in the fall or winter, you should be able to remove them the following spring. If you plant a tree in spring or summer, then you should be able to remove them in two to three months.
Mulching During Establishment
Mulching newly planted trees can help keep the soil in and around the root ball moist and promote root growth until the tree is fully established. Before mulching you should remove all excess soil from the top of the root ball as this could prevent water from reaching it. A two- to three-inch layer of mulch should be applied in a circle around the trunk at least to the dripline or outermost tips of the branches. Make sure that you keep the mulch a few inches away from the trunk to prevent bark decay. As the tree grows, you may need to continue to expand the diameter of the mulch until the tree is fully established.
Fertilizing During the Establishment Period
While there are many products on the market sold as “transplant aids” to be applied at the time of planting to assist with growth, proper irrigation is the best way to promote growth and establishment of your plant. Amending the soil with minerals like phosphorus and potassium will only help if soil tests show there is a deficiency of those minerals. Nitrogen has been shown to slightly help trees with growth during the establishment period, but concentrating on proper irrigation will pay the largest dividends in the end.
There is no need to fertilize field-grown trees at the time you transplant them as research has shown they receive little if any benefit from fertilization until 4 to 6 weeks after planting. If you will be unavailable in 4 to 6 weeks to fertilize, you can mix a small amount of slow release fertilize into the backfill at time of planting. Otherwise, in 4 to 6 weeks the same type of slow release fertilizer should be broadcast over the root ball and backfill soil based on the manufacturer’s instructions.
Pruning During and After Establishment
There is little or no evidence that pruning at or near the time a tree is planted has any positive impact on its growth or survival. If you selected a well-structured tree, then you should not need to prune it for several years after it is planted. You could prune your tree during the second growing season if you selected a tree with minor structural defects. If your tree will reach a height of 40 or more feet at maturity, then you will need to prune it regularly during the first 25 years to maintain its structure.