Population dynamics of moonworts has been studied extensively through annual monitoring, however relatively little is known about the phenology of Botrychium populations. The phenology of Botrychium gallicomontanum, a prairie species, and Botrychium mormo, an old-growth woodland species were monitored from June through September 1996 and 1997. A total of 240 B. gallicomontanum plants were monitored at the only known site of this species in northern Minnesota. A total of 284 B. mormo plants were monitored at two sites in the Chippewa National Forest in Northern Minnesota. Events during growth were divided into four stages including emergence, leaf separation, spore release and senescence. The number of above-ground plants of B. gallicomontanum peaked the first week in June and senesced rapidly following this peak. Though the population size declined in late June, the largest plants were found in early July with an average size of 4.8 cm. Similar results were found for B. mormo. B. mormo plants emerged in June and the population size peaked in early July, considerably earlier than previously thought. The largest plants occurred late in August with an average size of 2.7 cm. For both species, plants emerging early in the season completed development over a prolonged "seasonspan", or period of existence above-ground, whereas plants emerging later did so over a relatively short "seasonspan". The average "seasonspan" for B. gallicomontanum and B. mormo respectively was 5.5 weeks and 8.5 weeks. The juvenile stage is prolonged in B. gallicomonantum plants, whereas B. mormo plants have a much longer separation stage. Understanding the phenology will help us to more accurately predict the impact of management practices such as fire or timber harvest on these rare species.

Key words: Botrychium, management, moonworts, phenology, population demographics