Prolonged dormancy in the geophyte Allium amplectens on Vancouver Island

Prolonged dormancy occurs when a plant fails to appear above ground during the growing season. Although it may be an important life history trait of many geophytes, studies focusing on prolonged dormancy are infrequent and are concentrated on the Orchidaceae even though the phenomenon occurs in many taxonomic groups. We tracked individual plants of Allium amplectens (Amaryllidaceae) in permanent plots on Vancouver Island, which allowed us to determine rates of prolonged dormancy during a 4-year period. Dormancy rates per year averaged 38% and differed substantially among years. Over 70% of plants had a dormant period during the study. Dormancy periods of 2 years were almost as frequent as 1-year periods, and 8% of plants were dormant for 3 years. Plant density, which included small plants that we could not track in the plots, varied much more among years than did dormancy of tracked plants, suggesting that small plants may be especially prone to dormancy. High rates of prolonged dormancy and frequent multiyear dormancy indicate that this is an important life history feature of A. amplectens. We suggest that prolonged dormancy contributes to the ability of this species, and probably other species, to persist in dry habitats with fluctuating resources.