Blackberry bushes are often grown by backyard gardeners for the bounty of tart fruit they produce, but the plants can quickly turn rogue and become a nuisance weed. Remove the plants manually for quick elimination. If this isn't possible, resort to chemical controls. For the best results, begin chemical treatments of the blackberries during the spring growing season, though eradication of the shrub can be done at any time. Regardless of your approach, a quick response is necessary to keep the shrub from growing even more out of control.
Put on closed-toe shoes, jeans, long pants and gloves. Blackberry bushes are notoriously prickly and you can be seriously scratched if you're not wearing adequate protection.
Uproot the blackberry bushes using a spade. Work the tool in a circle around the center of the bush to loosen the roots and soil.
Treat the blackberry bush with glyphosate-based herbicide if manual removal is not feasible. Mix the herbicide with water according to its labeled guidelines and pour the solution into a standard garden sprayer.
Spray the center of the blackberry bush first, ensuring an even mist on all exposed surfaces of the plant.
Mist the herbicide onto the outside edges of the bush, ensuring you get the trailing branches that may be creeping along the ground. The blackberry bush will die within 10 to 14 days.