Agronomy and Horticulture Department


Date of this Version





Copyright 2009 American Society for Horticultural Science. Used by Permission.


Penstemon seed often shows an inconsistent or a low germination percentage. Although most select cultivars are propagated by cuttings, for export to other countries, seed is preferred. Three experiments were conducted to determine if soaking seed in gibberellic acid (GA3) would increase seed germination of Penstemon digitalis cv. Husker Red. GA3 concentrations used were 0, 10, 50, 100, 200, and 500 mg∙L–1 (first experiment); 0, 500, 1000, and 1500 mg∙L–1 (second experiment); and 0, 500, and 1000 mg∙L–1 (third experiment). The first and second experiments were conducted in a growth chamber, whereas the third experiment was conducted in both a growth chamber and greenhouse with seeds either covered or not covered by the mix. In all experiments,GA3 increased the percentage and rate of seed germination. The 1000 mg∙L–1 GA3 was the best treatment. In the third experiment, percentage and rate of seed germination were the highest for seeds grown inside of the growth chamber, probably as a result of the consistency of temperatures and darkness. In the greenhouse, the percentage of seeds that germinated and the rate of germination were similar whether or not the seeds were covered with mix and whether they received either the 500 or 1000 mg∙L–1 GA3 treatment.