Effects of Some Plant Growth Substances on Root Growth of Douglas-Fir Seedlings

Climate and soil factors, condition of seedlings, degree of competition, or any of a host of other variables may cause unacceptably poor survival of trees in forest plantations. Thus the possibility of planting failure often deters forestation attempts. In fiscal 1965, about 1,320,000 acres (Anonymous 1966) were planted to forest trees in the United States. It is estimated that 80 percent of these acres will support acceptable stands. However, many Western States have very acute survival problems. For example, during a 5-year period, 12 million forest seedlings were planted in California (Stone 1955). Less than half survived. The survival of many plantings in Idaho is less than 10 percent after a single growing season (Loewenstein and Pitkin 1961). Seedlings that succumb during the first year or two very often have been supported by root systems failing to develop appreciably after outplanting. If it were possible to induce early and vigorous root growth in planting stock, survival might be improved. The use of synthetic growth substances to regulate seedling development (Audus 1959, Koslowski 1962, and Osborn 1960) may be economically feasible. Such substances have already proved beneficial in various facets of forestry and allied fields (Snow 1959), and still further uses are likely to be found. These substances are now used rou tinely as selective herbicides for stimulating vegetative propagation, preventing fruit drop, fruit thinning, producing parthenocarpic fruit, flowering control, and in many other ways.

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Author(s): Howard Loewenstein, Harold R. McEwen, Franklin H. Pitkin

Publication: Tree Planters' Notes - Volume 19, Number 3 (1968)

Volume: 19

Number: 3