Trees are the most important and valuable element of the home yard and landscape. Forming the superstructure of the garden or landscape, trees provide a stage upon which the shrubs, groundcovers, vines, and color plants play out their various, supporting roles. Trees also enhance the environment, provide numerous amenities, convey a sense of warmth, hospitality, and serenity, and add significantly to the dollar value of the property. However, to fully realize the potential amenities and benefits trees can provide, one must select, plant, and maintain them with the utmost care.
It is most important to select the right tree for the right place in the home yard or landscape. When selecting a tree, know its ultimate size, growth form and characteristics, as well as its adaptability to a particular environment, and be sure it is compatible with the intended site and use. Give trees enough space so that when they reach full size, branches and roots are not clashing with adjacent structures, trees, pavement, utility lines or other plants. Select a tree with growth characteristics desired to fit the intended use, whether it is for shade, parkway, screen, windbreak, or landscape accent. Although most trees are tolerant of a wide variety of environmental conditions, such as temperature, wind, soil, humidity, water, pests and fire, some have unusually limited conditions in which they will grow well.
When selecting trees in the nursery, look for healthy, not overly vigorous, individuals with a well-formed crown in proportion to the size of trunk and container — not too large, not too small. Future main branches should be well spaced up and down the trunk and attached at wide angles. The trunk should be widest at the base and gradually taper toward the top. Ask the nursery professional to remove the container so you can inspect the roots. The root system should fill most or the entire container without being root bound. Avoid selecting tress with diseased, damaged, or severely kinked, circling, or girdling roots.
Dig the hole to a depth about two inches less than that of the soil in the container or root ball but at least twice as wide. Carefully remove the plant from the container and place it in the hole. Use the same soil from the hole to backfill around the root ball without any added amendments. Then water thoroughly to firm the backfill and remove large air pockets (avoid compacting the soil). Mound the excess soil to form a water basin three inches high and at least as wide as the hole. Place a two-inch layer of mulch in the basin and water thoroughly. Keep the root ball and surrounding soil moist, but not wet, for 6 to 12 months. Keep grass and weeds away from the stem and root ball.
Remove the nursery stake at planting. If the tree stands without support, do not re-stake. If it tends to lean, try thinning out the crown to reduce weight and wind resistance. If it still leans after thinning the crown, it must be staked. Use two, sturdy stakes — one each on opposite sides of the trunk — positioned so that a line drawn between them would be at right angles to the prevailing wind. Make the stakes as short as possible, barely high enough to hold the tree upright under calm conditions. The tree should return to vertical after the wind has bent the top. Loosely tie the trunk to each stake so that it is allowed to move a little.
To determine the proper point at which to tie a tree, hold the trunk in one hand, pull the top to one side, and release. The height at which the trunk will just return to upright when the top is released is the point at which to attach the ties. Ties should have a broad surface to minimize rubbing or girdling and have some elasticity to provide greater flexibility and support. As the tree grows and becomes better established, remove or lower ties and shorten the stakes so they do not rub against the trunk and cause rubbing or girdling injury. Remove stakes as soon as possible, probably by the end of the second growing season.
Heat-loving subtropicals should be planted in late spring so that they can take advantage of the long summer growing season. A variety of deciduous trees is usually readily available as bare-root plants. They are normally less expensive than containerized trees and grow just as well if handled and planted properly. For bare root trees, make the hole large enough to spread the roots out evenly without bending or crowding, and plant as you would for container-grown trees.
When to water and how long to water depends on the weather and type of tree and soil. Trees vary from species to species in their water needs. Also, they generally need more water during the warmer months when growth is most active and water loss is greatest. However, even in the cooler months it might be necessary to water if rains are insufficient. A tree will require about the same amount of water regardless of the type of soil in which it grows. However, lighter, more frequent applications are necessary on sandy soils, while heavier but less frequent applications are called for on a clay soil. The general rule of thumb is to water established trees as deeply but as infrequently possible, usually when the soil one to two inches deep dries out. Apply enough water each time to wet the soil at least 12 inches deep. Use a shovel or probe to check water infiltration if necessary. Once established, trees in lawns or flower and shrub beds usually survive adequately on the water given to the surrounding grass and other plants.
Most healthy, mature, well-established trees need little fertilizer. However, fertilizer is usually beneficial to promote more rapid growth and faster establishment in newly planted trees or if older trees are showing deficiency symptoms.
Evenly broadcast a high-nitrogen, but complete, fertilizer (15-5-15, 11-4-8, etc.) at the recommended label rate over the soil surface at least out to the drip line of the tree. Follow label rates, or 1/3 to 1/2 pound of nitrogen per inch diameter of the trunk. Fertilize newly planted trees after planting. Fertilize older, established trees with one-half the total amount desired in spring prior to most rapid growth and then again with the remaining one-half in mid summer. Irrigate thoroughly after fertilizing to move the nutrients into the soil.
Mulch is beneficial to trees and most other plants. Fallen leaves from trees and other plants can remain on the ground to form a natural mulch where possible and practical, or apply an organic, commercially available mulch.
Donald R. Hodel is an environmental horticulturist for the University of California Cooperative Extension, Los Angeles County. His research focuses on selection, planting and management of woody plants in the landscape with a special emphasis on plant water use, trees and palms. He is considered a world leader in palm taxonomy and horticulture. Hodel has authored/co-authored more than 50 peer-reviewed journal articles and more than 250 trade or popular articles about selection, planting and management of woody landscape plants. In addition, he has authored six books. He has conducted more than 250 presentations to industry groups, professional and honor societies, university and other governmental agencies, and consumers about various aspects of landscape plant selection and management. He is a member of the American Society for Horticultural Science, International Society of Arboriculture, International Palm Society, California Association of Nurserymen, California Landscape Contractors’ Association, Southern California Horticulture Association and Alpha Xi (the collegiate honor society of horticulture). Hodel has been an invited presenter at numerous international and national meetings, conferences and symposia. He can be reached via e-mail at firstname.lastname@example.org