The Effect of Living Grass on the Growth of Longleaf Pine Seedlings in Pots

Abstract

The early stunted growth of longleaf pine (Pinus palustris Mill.) seedlings has been attributed by various writers to a number of causes. Mohr ('96) regarded their slow growth as a natural phenomenon and divided the growth of longleaf pine seedlings into two major periods-the first period of slow growth lasting six years and the period of rapid growth beginning with the seventh year. Siggers ('32) attributed the slow growth largely to the action of the brown-spot disease, Septoria acicola (Thtim.) Sacc. (now classified as Scirrhia acicola [Dearn.] Siggers). Pessin ('38, '39) has presented evidence that the competition of the native vegetation accounts for considerable retardation of the growth of the pines; he found that when longleaf pine seedlings, protected from brown-spot by spraying, were freed from competition with the native grasses, their growth increased substantially within two years after treatment, over that of similarly sprayed seedlings surrounded by grasses. The stunted condition of many longleaf pine seedlings under natural conditions may well be due to the above factors operating together, with one or another exercising the greatest effect at various times. In view of the marked response of pine seedlings to release from competing vegetation, however, it may be assumed that the native vegetation plays an important role in prolonging the period of dwarfness in the pine seedlings. To determine more precisely the nature of the competition, an experiment was designed to study the behavior of longleaf pine seedlings when grown in containers under known conditions of moisture, both with and without grasses, and with varying quantities of mineral nutrients in the containers occupied by both seedlings and grasses.