Oregon grape (Mahonia aquifolium) grows wild in several areas of North America. It also is frequently planted as an ornamental, for it's dark blue berries, holly-like leaves and small yellow flower clusters. When poorly managed or growing wild, the Oregon grape can grow spindly or spread wide, preventing the growth of more desirable plants. Its dense foliage attracts grazers and harbors insects and vermin. Although widespread in certain areas, Oregon grape is fairly easy to kill. To prevent wild Oregon grape from re-establishing itself, replant the area with another more desirable plant that grows well in your area.
Cut the Oregon grape back to ground level, using lopping shears for vines that are less 2 inches thick and a pruning saw for larger vines.
Paint the cut stump with a small brush dipped in a 2, 4-D, dicamba, glyphosate or triclopyr herbicide. Paint the stump immediately after it has been cut. The sooner the herbicide is applied, the more effective it will be. If more than three minutes pass, cut the stump 1/4-inch lower before painting. Coat the stump well, but avoid runoff. Any of the above herbicides will kill all vegetation they come into contact with.
Discard the cut foliage in a garbage can or compost pile.
Monitor the former patch for regrowth. Cut and paint it as necessary.
Dig up the roots when the Oregon grape produces no more growth, if you intend to replant the area.