Seed Dormancy and Germination Ecology of Calycanthus floridus L., a Species with Threatened Status in Kentucky

The seed germination ecology of Calycanthus floridus (Eastern Sweetshrub) has not been formally investigated. The purposes of this study were to determine the type of seed dormancy found in the species, the most effective method of breaking this dormancy, and the environmental conditions producing maximum germination. We employed a variety of standard treatments to determine the specific type(s) of dormancy present, as well as treatments to determine effective dormancy-breaking mechanisms. We determined that seeds possessed physical dormancy (PY) imposed by a water-impermeable seed coat. Mechanical scarification was the most effective method of breaking PY; submersion in acid was also moderately effective. Seed germination following scarification can occur over a wide range of temperatures. There is no light requirement for seed germination. This study represents the first case of physical dormancy reported for the genus and only the second for the family.