When you think of blackberries, you may think of blackberry cobbler and blackberry pie, but for some people, blackberries are synonymous with a bush that moves in, reproduces quickly and is difficult to get rid of. Blackberry brambles grow from the roots, and create new plants wherever old canes touch the ground. To kill blackberries without pesticides, you have to get rid of the roots.
Put on protective clothing when dealing with blackberry canes. Blackberries have sharp thorns and can scratch or cut you if you do not wear protective clothing.
Cut canes back to ground level in the spring when plants are at their most active. The easiest way to do this is to mow them down to the ground level. This will prevent new canes from rooting.
Dig up roots using a shovel, garden cultivator and rake.
Continue to observe the areas where you have removed your blackberries. Dig up any emerging canes from roots that you may have missed.