Influence of Light and Temperature on the Germination and Seedbed Ecology of Common Mullein(Verbascum thapsus)

Germination of common mullein(Verbascum thapsusL.) in relation to constant and alternating temperatures, and light quality and duration was studied. In the dark, optimum germination occurred with 8-h warm periods of 30 to 40 C alternating with 16-h cold periods of 15 to 35 C. In the dark, no germination occurred below 10 C. With light during the 8-h warm periods, germination occurred at temperatures from 2 to 40 C, alternating with 0 C cold periods. The range of optimum temperatures for germination was also greatly expanded with light. Exposures to 24-h periods of red light, followed by incubation in the dark, produced the same germination response as 8 h of white light daily. Common mullein seeds germinated on the surface of the soil even though the seeds did not have mucilage.