I sampled the plant communities associated with Garry oak (Quercus garryana) in British Columbia in order to develop a classification for use in resource management. Garry oak ecosystems have been designated as critically imperiled in British Columbia. My methods employed some quantitative aspects, but were largely subjective in order to assemble a numerically-adequate data base, apply a landscape approach and include a wide geographic coverage. Although some facets of my study were influenced by European phytosociology, both methodological affinities and the results of objective comparisons place the classification in a scientific context with other studies from the Pacific Northwest oak woodlands. Forty-three (43) plant communities were identified and are described in detail. They consist of 27 communities in a category named for native plant species and 17 communities named for introduced species, organized in two categories of previous disturbance. Similar plant communities are recognized from the literature on other oak woodlands in the Pacific Northwest. The ecosystem relations of the plant communities are depicted on a subjective basis from the collected field data, supplemented with objective results at a broad level. Ecological hypotheses are suggested, along with management interpretations for each of the plant communities. Preservation and active management are emphasized in a management strategy presented for the Garry oak habitat as a whole.