The success of the growth of a tree depends highly on the soil in which it is planted. The first critical element is soil drainage. To test for drainage, dig a hole 18 inches in diameter, 12 inches in depth. Fill the hole with water and let it drain. After it has drained, fill it again and time how long the hole takes to empty. 1/2 to 4 hours is good, 5-12 hours in moderate. If over 12 hours, there is a problem. If drainage time is greater than 12 hours and the site will still be used, a raised bed of appropriate size may be the only way the tree can be grown successfully.
Tree roots can extend to three times the height of the tree. Most roots live with the first 6 to 12 inches of the soil. Because of the anticipated size of the tree, it may not be desirable to fully control all the quality and type of soil in which the tree is planted. Surface mulch, however, will add to the nutrients just above the roots as well as help conserve water. Eventually the mulch will break down to be come part of the soil. When mulching, keep the mulch away from the base of the trunk.
In addition to the quality of the soil, nutrients in the soil can effect the tree health. Fertilizing of ornamental trees is not usually necessary, but nutrient deficiencies as evidenced by abnormal leaf conditions or poor growth can be corrected by adding fertilizer. Methods for diagnosing nutrient deficiencies include visual symptoms, soil analysis, and leaf analysis. Fertilizing Landscape Trees, Publication 8045, from the University of California Agriculture and Natural Resources Department describes how to identify deficiencies and how to correct them.
One of the methods described for diagnosing deficiencies is the soil test. However, unlike vegetable crops where nutrients needs have been thoroughly researched "... there are no research-based guidelines available to compare soil nutrient levels with landscape tree growth and needs. Soil tests are more useful for determining pH, texture, total salts, and toxic levels of boron, chloride, and sodium" (Fertilizing Landscape Trees). If a soil test is desired, there are relatively inexpensive soil test kits available at nurseries and nursery departments of larger stores. More reliable soil analysis at a significantly greater cost can be obtained from analytical laboratories listed in the phone directory. Whether using a test kit or an analytical laboratory, the method in which the soil is sampled is critical. Detailed directions can be found in Fertilizing Landscape Trees.