Effects of environmental factors, especially light, on eastern black nightshade seed germination were studied under growth chamber conditions. Germination occurred only when temperatures were 20 C or higher for 12 to 24 h d⁻¹. Optimum germination occurred within the constant temperature range of 28 to 33 C or with alternating temperatures of 30/25 and 35/30 C. In the dark, eastern black nightshade germination was poor except at high alternating temperatures of 30/25 and 35/30 C. Seed germination was enhanced by light when temperatures were suboptimal. Imbibition was a prerequisite for response of eastern black nightshade seed to light. The light requirement for eastern black nightshade germination was partially overcome by cold stratification, gibberellic acid (GA₃), and high or alternating temperatures. Germination of eastern black nightshade seed was promoted by short exposure to sunlight but was inhibited by prolonged exposure, especially when irradiance was high.

Nomenclature: Eastern black nightshade, Solanum ptycanthum Dun. SOLPT.