When planning the installation of trees in a residential or commercial setting, the first consideration should be their intended use. In home landscaping, this may include such concerns as the need for shade, for framing a house or providing ornamental color, for constructing a windbreak or privacy barrier, or for providing a center of interest in a
garden area. Commercial uses may include lining an entrance driveway thereby directing traffic flow, shading parking areas, concealing unsightly objects such as dumpsters, or for the production of fruit or lumber. In all cases, it is important to know the tree's growth rate and ultimate size before making selection decisions so that it will fit its location at maturity.
Once the functions of the trees have been determined, attention should be directed to their planting sites. Some trees have characteristics which may require special considerations. A large canopy tree, for example, should never be planted under overhead wires since the shape of the crown will ultimately be ruined by continuous pruning to keep the wires free of branches. Small trees which will become large at maturity should not be planted under the eaves of roofs, nor planted too close to walls. Similarly, the roots of a tree may be irreparably damaged if it is planted too close to underground utility lines which may one day need to be excavated for repair.
Deciduous trees which periodically drop most of their leaves, and those which produce large numbers of flowers and fruits, should not be planted where they will eventually overhang roof gutters or swimming pools. In these cases, the maintenance requirements of underlying areas may far outweigh the trees'shade or ornamental values. Avoid installing trees that are known to shatter or blow over in high winds. Trees which have sap or fruit with staining properties should not be planted adjacent to sidewalks or parking areas, and those having dense shade should be avoided in areas where underlying , sun-loving gardens are planned. The type and amount of shade provided by tree canopies must be compatible with underplantings.
Most trees have the majority of their roots in the top 12-18" of the soil where nutrients are most plentiful. In some species the surface roots may become quite large as they mature and cause damage to sidewalks, driveways, and even building foundations. The roots of some trees are known to seek out water agressively and may grow into and clog water and sewer lines. These varieties should be planted in open areas where their roots can spread and not interfere with other plantings or structures. As can be seen, the rooting habits of trees are also important considerations when planting decisions are made.
Trees which have thorns or spines, irritating sap, or poisonous leaves, seeds, or fruits should be planted only where
they do not interfere with pedestrian traffic or children's play areas. Often these trees have desirable attributes such as unique growth habits or flowering characteristics, but they must be planted with care and with the knowledge of their potential hazards.
Fortunately, there are trees for all situations. Before deciding what to plant and where, observe as many trees as possible in your surrounding community where similarities of soil and exposure exist. This is especially important in areas with high caliche content. Know what the trees are, how large they grow, how long they have been there, do they appear healthy or under constant stress, are they appropriate for the site and use you have in mind? Finally, visit your local botanical garden and nurseries for advice. With a little foresight and thought, your arboreal investments will yield long-term dividends.
After determining that there are no utility or water lines underlying the planting site, a test should be conducted to evaluate the drainage potential of the soil. This is extremely important since poor drainage can cause root-rot, stunting of growth, or even death of the tree. To test the porosity, a hole should be dug approximately 12-18" in diameter and 18" in depth, then filled with water. If the water seeps out in an hour or less, the soil has very good drainage. If it is dry within a day, the drainage is considered moderately good. If the water is still present after a couple of days, the drainage is poor and another planting site should be selected.
When a location with adequate porosity is found, a planting hole should be dug 2-3 times the width of the tree's current root mass and only as deep as the root ball. Eighty per-cent of tree problems arise from their being planted too deeply, a practice which increases the incidence of stem and root disorders. The sides and bottom of the pit should be slightly broken to allow developing roots to penetrate more easily into the field soil. If container grown, the trees should be carefully removed from the pot so as not to disturb the existing roots or soil mass. If roots are encircling the soil, they should be teased apart so they may be spread in the planting hole. If this is not done, they may continue their spiral growth pattern and cause lethal problems for the tree as it matures.
After placing the tree in the hole and spreading any circling roots, soil may be back-filled into the pit. This back-fill should be mixture of the field soil removed from the hole and either wet peat moss or compost. It should be rich enough to encourage lateral root growth into it from the original root mass, but not so different from the surrounding soil that it becomes an artificial container which restricts further root development. The back-fill should
then be packed firmly around the tree to remove any air pockets.
After the fill has been added, a berm or ridge of soil 5-6" high should be constructed surrounding the tree. This will form a basin to help catch rainfall and make watering more efficient. To be most effective, it should encircle the tree a couple of inches outside the perimeter of the pit to encourage roots to grow into the surrounding soil. The basin
should then be filled with mulch which acts to reduce water loss from the soil, keeps the temperature around the new roots more stable, and discourages the growth of weeds which compete with the new tree for water and nutrients.
During or immediately after planting, the tree should be watered thoroughly. It is recommended that one year of establishment watering be given for each 1" of trunk diameter. This involves watering twice a week for the first 3 months, then once a week for the remainder of the year. For a tree with a 2" trunk diameter, this schedule would be
carried on through the second year. Since most native trees are moderately to highly drought tolerant, they will need little or no further watering after this initial period of establishment. However, in highly windy areas or on very poor soils, a weekly soaking would be beneficial.
Staking of trees for initial support or protection may be necessary in open, windy situations. For small plants, a single supportive stake on the windward side is usually sufficient; for larger trees, 3 stakes with wire supports placed equidistantly around the trunk may be necessary. In either case, care must be taken that the support wires do not injure
the bark either during or after installation. Stakes and supports should be removed after one year since flexing of the tree caused by air movements is necessary
for building girth, strength, and proper tapering of the trunk.
Small container-grown trees generally require no pruning at the time of planting other than the removal of dead or injured branches. Plants removed from the wild may require 25-40% of their functional leaves removed by pruning of branches so as to reduce water consumption while the root system re-establishes itself. It is recommended that nursery professionals be consulted on pruning techniques for the particular type of tree that has been selected.
It is not recomme
nded that fertilizers be applied at the time of installation, though transplant shock regulators and root stimulating hormones are beneficial. Once new growth is obvious, the application of an all-purpose, time-released fertilizer such as Osmocote would be advantageous. Once applied, such fertilizers are slowly released with each watering and reduce the possibility of injury due to over-fertilization. Most native trees will subsequently require semi-annual applications of fertilizer to look their best, especially on thin or rocky soils.
During the first year of establishment maintenance, insect pests may be a problem in periods of stress caused by drought, or following heavy rains. The insects most commonly encountered are scales, mealybugs, aphids, and mites. All can be controlled easily through the foliar application of readily available insecticidal sprays such as Malathion, Diazinon, and Orthene. Once established, native trees will be resistant to most of these pests and insect control should not be a problem.