Influence of temperature gradients on pale and purple coneflower, feverfew and valerian germination

Abstract

Seeds of pale coneflower (Echinacea pallida), purple coneflower (Echinacea purpurea), feverfew (Tanacetum parthenium), and valerian (Valeriana officinalis), classified as "old" (1-year-old seed) or "fresh" (seed crop produced in the current year), were germinated at 62, 65, 69, 72, 75, 78, 82, 85, 89, and 92°F, (16.7, 18.3, 20.6, 22.2, 23.9, 25.6, 27.8, 29.4, 31.6, and 33.3°C). The optimum germination temperature, defined in this study as the temperature range within which the percent germination is greatest in the shortest period of time, was determined. Old and fresh pale coneflower seed germinated optimally after 5 days at 69°F. Old purple coneflower seed required 5 d at 78 to 82°F, but fresh seed germinated optimally after 3 days at 75°F. Old feverfew germinated optimally after 5 days at 65°F, but fresh seed germinated to its optimum after 5 days at 69°F. Old and fresh valerian seed germinated to its optimum after 3 days at 75°F.