Habitat requirements of the yellow glacier lily, Erythronium grandiflorum Pursh, were studied at 38 sites in southern British Columbia and southwestern Alberta. At each site we recorded densities of E. grandiflorum growth stages from seedling to flowering, environmental characteristics of the site, and percent cover of associated plant species. We carried out detrended correspondence analysis (DCA) of the sites based on cover of associated species, and examined rank correlations between site environmental variables and site ordination scores. Variation among sites was related primarily to elevation and the presence of deciduous vs. coniferous trees. All growth stages of E. grandiflorum were less abundant in coniferous forests than in open areas or sites with deciduous trees, suggesting that evergreen canopies restrict the species on many sites where it could otherwise grow. Although E. grandiflorum populations were most commonly found in subalpine meadows, they flowered more abundantly in low-elevation populations. Recruitment was frequent, with seedlings occurring at many sites; we also showed that detached bulb segments can give rise to new ramets. The present widespread distribution of E. grandiflorum may derive from a post-glacial period with extensive meadow habitat that was favourable for rapid spread.Key words: canopy cover, elevation, yellow glacier lily, post-glacial migration, subalpine meadows.
