David Susko
Showy tick-trefoil (Desmodium canadense) is a common, widespread, native leguminous species found in tallgrass prairies in Michigan and southern Ontario, whose requirements for germination were previously unknown. The aims of our study were: 1) to determine the extent to which seeds are dormant at maturity; 2) to evaluate several physical (manual scarification), thermal (chilling, moist and dry heat), and chemical methods (sulfuric and hydrochloric acid, ethyl alcohol) for breaking dormancy; and 3) to assess whether dormancy is broken following dry storage or burial in soil. Nearly all (97-100%) hand-scarified seeds germinated, whereas only < 10% of nonscarified seeds germinated, indicating that seeds of D. canadense possess physical seed dormancy at maturity. Dry storage, burial in soil, and exposure to ethyl alcohol, moist heat, and dry heat failed to promote germination regardless of duration. Dormancy breaking methods that increased germination percentages included chilling for 8 wk (12-18%), exposure to concentrated sulfuric acid for 5-30 min (64-99%) and exposure to concentrated hydrochloric acid for 60 min (12%). Hence, seeds may be released from dormancy by exposure to cold winter temperatures or via scarification of the seedcoat by particles of soil on the seed surface.
Keywords: SHOWY TICK-TREFOIL, DESMODIUM CANADENSE, GERMINATION, PHYSICAL DORMANCY, TALLGRASS PRAIRIES