Published online by Cambridge University Press: 19 September 2008
Seeds of the narrow-endemic Solidago shortii and of the geographically-widespread S. altissima and S. nemoralis buried in December 1993 were exhumed in June 1995 and given 10 cycles of 1 day wet/5 days dry, 9 of 2/5, 8 of 3/5, 7 of 4/5 and 6 of 5/5 in light at 30/15°C; the control was kept continuously wet during the experiment. Seeds of the three species incubated on wet substrate for 3, 4 or 5 days germinated to ≥47% during the first cycle. On the other hand, seeds kept moist 2 days germinated to only 4–26% in the first cycle, and none kept moist for 1 day germinated. Cumulative germination percentages of seeds of all three species at the end of the final cycle of the 1/5 treatment were 0–4%. In the 2/5 treatment, cumulative germination percentages of S. altissima and S. shortii seeds at the end of the final cycle were 50 and 41%, respectively, but that of S. nemoralis was only 4%. For all three species, cumulative germination percentages were ≥55% at the end of the final cycle of the 3/5, 4/5 and 5/5 treatments. Control seeds of the three species germinated to 85–99% after 2 weeks, and no additional seeds germinated during the remainder of the experiment. High percentages of seeds were viable in the treatments and control at the end of the experiment; however, some seeds of S. nemoralis and S. shortii given 1/5, 2/5 and 3/5 treatments became dormant. The ecological implication of this study is that seeds of the three species will not germinate on the soil surface after brief rainfall events in summer. The germination response of the narrow endemic is similar to that of its two geographically-widespread congeners.