There is a close relationship between root system characteristics and the relative fire resistance of Douglas fir forest zone species in southern interior British Columbia. Susceptible species are usually those that have fibrous root systems or produce stolons or rhizomes which grow above mineral soil. Moderately resistant species usually have fibrous roots with rhizomes which grow less than 5 cm below the mineral soil surface. Resistant species are those that have rhizomes which grow between 5 and 13 cm below the mineral soil surface and those species with taproots which are able to regenerate from below their crowns. Both timber milkvetch and lupine are undesirable range plants and yet both may increase after a fire.