Blackberry bushes root so well that the tip of a blackberry plant that touches the ground will sprout new roots and form a new plant. Blackberries will also reproduce through nodes--underground runners that produce new plants. The roots can reproduce so vigorously that they can become invasive. Controlling blackberry vines and canes can be a challenging task.
Kill existing blackberry plants by spraying the canes and leaves with an application of a systemic herbicide containing glysophate.
Wait until the plants have died. Dead blackberry canes will turn brown, and the leaves will become brittle.
Mow down blackberry plants to ground level using a tractor with a mowing attachment and dispose of the canes. Do not compost canes, because they still have herbicide residue on them.
Paint the exposed stems with glysophate.
Observe the area where you have cut back the canes for new plants to emerge. Dig up these plants to remove the roots and nodes from the ground. This process is known as grubbing.