Stimulation of early height growth in longleaf pine with growth regulators

Longleaf pine (Pinuspalustris Mill.), although it has many excellent qualities, is not extensively planted because of its extended seedling "grass stage" accompanied by poor field survival. Treatments with cytokininlike substances in spring and early summer stimulated seedling height growth, and this effect was enhanced by gibberellic acid (GA3) and DPX 3778, an experimental triazinone derivative that is synergistic with gibberellins. The synthetic cytokinin benzyladenine and other active purine derivatives, although potent, tended to cause bud proliferation and death. A seaweed extract with cytokinin activity, Cytex, proved effective without the deleterious side effects. A promising technique is thus to apply combination sprays of Cytex, GA3, and DPX 3778 in the nursery to stimulate height growth during the 1st year in the field.