A blackberry plant is an irritating garden invader if you did plan to, or do not wish to, grow the berries. It is a prickly, pushy, fast-growing plant that is not easily removed. Mowing it, burning it or bulldozing it all encourage new growth and cell production. Burning encourages the plant to re-sprout from rhizomes, while bulldozing spreads the plant by scattering the roots and stems around, which then re-sprout in new locations. The best way to get rid of a blackberry bush is to completely remove the plant, root systems and all fragments, then rot away the stump. Using herbicides, though not ideal, is another option.
Digging out plants is difficult and you should wear heavy-duty gardening gloves to protect your skin from the brambles. Use pruning shears to cut off the bushes near the ground, removing them as fast as possible so the roots won't start to spread.
Use a shovel to dig out the blackberry bush stump. Make sure that you locate each small root to rip it from the ground, digging deep to find them. Throw out everything you dig up; leaving it there can cause future growth.
Boil a gallon of water per blackberry bush, then pour it over the area you removed the bush from. Repeat this at least three times. This will help encourage the root system to rot out.
Till the ground repeatedly to eliminate the rhizomes and root pieces. It is important to do it multiple times because doing it once will just spread it around to grow in a larger area. Till it deeply, and dispose of the tilled dirt and blackberry pieces.
Keep an eye on the area where the blackberry bush was. If the bush begins to grow back, try using herbicides as an option. Good products include triclopyr and glyphosate, that can be found at a local gardening store. Make sure to follow the directions exactly to get the best benefits. Do not use it when the plants have fruit that may be eaten, or when the plant is dormant during the winter. Hit sprouts in the spring or summer with the herbicide.