Davidsonia, Vol 14 (4): 121-128, 137-144 Figures: 8-14, rear cover. Authors: Gary J. Lewis and Gary E. Bradfield (Department of Botany, UBC) Abstract: While distinct floristic and ecological patterns have been reported for ultramafic (serpentine) sites in California and Oregon, those of British Columbia are muted which is thought to be related to the moderating influence of increased precipitation, a short time since glaciation, and the presence of non-ultramafic glacial till over ultramafic sites. Despite these factors, we found clear floristic and ecological differences with respect to soil type at our study site on Grasshopper Mountain, part of the Tulameen ultramafic complex in southern British Columbia. Ultramafic soils support 28% of the local species richness and host more rare taxa than non-ultramafic soils. Many species show patterns of local restriction to or exclusion from ultramafic soil habitats. Patterns of plant family diversity also show differences between substrates.