Reproductive capacity, germination and survivorship of Lithospermum caroliniense on Lake Huron sand dunes.

The flowering of pin (long-styled) and thrum (short-styled) plants in populations of Lithospermum caroliniense (Walt.) McMill. was synchronized and both morphs had an extended period of flowering. The plants produced a large number of flowers that did not set seeds - hence the seed production per plant was very low. The seeds showed strong dormancy. Even under natural conditions, only 19% of the seeds produced seedlings. However, seedling survival was relatively high probably due to rapid root growth to deeper layers where moisture was not limiting. The probability of survival of seedlings increased with age; survival of seedlings, juveniles and adults after 2 years was 39, 68 and 98%, respectively. The dry weight of roots increased from 10% in June to 42% in September whereas the proportion of biomass contained in leaves, stems and hypocotyls decreased with age.