The Influence of Growth Stage on the Response of Red Clover (Trifolium Pratense L.) to Gibberellic Acid

The response of seedling and first harvest year plants of red clover (Trifolium pratense L.) to treatment with gibberellic acid (GA) at various growth stages is described. Seedlings sprayed before the seventh leaf stage developed into single‐stemmed plants; treatment with GA at the third‐ or fourth‐tiller stage resulted in final stem numbers similar to those of controls. Emergence was earliest, and the number of heads per plant greatest where sprayings were delayed until the third‐ or fourth‐tiller stage. In first harvest year plants significant increases in the number of heads per stem were obtained with certain treatments, especially those which had two applications of 0.5 mg. GA per plant during the elongation of the first four internodes. This was related in all treatment groups to modifications of the branching pattern, and also to the increased incidence of multiple heading. Earlier emergence resulted from treatment at all growth stages, the effect being maximal where three well‐spaced sprayings were applied during active stem extension.