FACTORS AFFECTING GERMINATION OF DOGFENNEL (EUPATORIUM-CAPILLIFOLIUM) AND YANKEEWEED (EUPATORIUM-COMPOSITIFOLIUM)

Laboratory studies were conducted to determine the effect of various factors on germination of dogfennel and yankeeweed. Dogfennel seed were found to be strongly photoblastic with no germination in the dark. Yankeeweed seed were moderately photoblastic, with 12% germination occurring in the absence of light. Germination for both species increased in response to red light (650 nm), indicating phytochrome regulation. At the soil surface, dogfennel and yankeeweed emergence was 40 and 48%, respectively, but declined rapidly with increasing soil depths where dogfennel germination was lower than that of yankeeweed. Yankeeweed germination was 60 to 75% from 10 to 30 C while dogfennel germination was 45 to 70% between 15 to 30 C. Both species germinated over a broad range of pH (6 to 10) with the highest germination occurring at pH 8. Yankeeweed and dogfennel were moderately tolerant to water stress, but yankeeweed tolerated higher water stress than dogfennel. Both species germinated over a wide range of conditions, possibly enhancing adaptation to many diverse environments.