Unlike many plants, trees generally take care of themselves after planting. There are some varieties that need more attention than others and there are some care tips that can help ensure their future health and value.
Trees should be watered thoroughly at planting time and once a week (adjusted for significant rain) through the first growing season. Water more often on sandy soils or during very hot, dry weather. The water must penetrate 6 to 12 inches to reach most of the tree's roots and to encourage deep rooting.
So, a light sprinkling is not enough, you must do more than simply wetting the soil surface. During times when irrigation water is limited due to drought, be sure to give adequate water to your trees or they may decline in health and die. Lawn that dies due to lack of water can be replaced fairly quickly; trees cannot.
It is recommended that you stake newly-planted trees that are over 2 to 4 feet tall, especially if they need to endure a lot of wind. When staking trees, do so loosely because some bending is needed for the trunk to develop naturally. Anything that wraps around the trunk, like wires or cords, should be well-padded to avoid damaging the tree's bark and outer growing layers. Stakes should be removed after 1 or 2 years. If the root system is not well-established by that time, it is unlikely that it ever will be.
Mulching newly-planted trees and established trees is a good way to ensure their health. Create a 4 foot (or larger) circle of wood chips, compost, or other coarse organic mulch around the tree. It should be 4 inches deep in order to help control weeds, keep roots moist, reduce soil compaction, and to provide a buffer between the tree’s trunk and mowing. If the lawn is already established around the tree, place the mulch directly on the turf. Any grass not shaded-out by the mulch can easily be pulled.
Fertilization is not necessary for most trees. It is generally not recommended to fertilize a tree at the time of planting and for at least a year or two after planting. If fertilization is to be done, wait until twig growth has returned to a normal rate. This indicates that the tree is no longer suffering from transplanting shock. Use a complete, granular fertilizer spread on the surface under the tree's crown and water it in well. Avoid using "weed-and-feed" fertilizer-herbicide combinations around trees since these are designed to avoid injuring grass but may damage trees.