Hairy nightshade is the most widespread nightshade species in North America. Increased knowledge of hairy nightshade germination biology would facilitate development of an optimum control program. Germination of hairy nightshade seeds as affected by environmental and chemical factors was studied under greenhouse and controlled-environment growth chamber conditions. Hairy nightshade seeds were in an innate dormant state when initially separated from the berries. Moist compared with dry storage was more effective for breaking dormancy at 4 C, but dry storage was more effective at 17 C. Hairy nightshade seeds germinated equally well under both a 14-h photoperiod and continuous darkness. These germinated at constant temperatures ranging from 19 to 39 C, with optimum germination attained between 27 and 33 C. Germination markedly declined as osmotic potential of the germination medium decreased. The optimum pH range for germination of hairy nightshade seeds was between 6 and 8, although some seeds germinated at pH 4 and 9. Maximum hairy nightshade emergence occurred with seeding depths of 2 cm or less. No emergence occurred when seeding depth reached 8 cm.

Nomenclature: Hairy nightshade, Solanum sarrachoides Sendtner SOLSA.