Blackberry bushes can either be a blessing or a burden in the garden or landscape. If undesired, they are very difficult to get rid of, because simple things such as a mowing it only encourages growth. One of the best and least expensive ways to remove one of the plants is to completely remove every part of it, then dissolve the stump in boiling water.
Wear heavy-duty gardening gloves to make sure your hands don't get harmed by the sharp branches and brambles. Use pruning shears to cleanly cut the stump off near the ground, cutting off the entire top part of the blackberry bush.
Insert the sharp tip of a shovel down into the ground, about 2 feet to the side of the stump of the blackberry bush. Push it upwards, doing your best to uproot the plant. Remove as much of the stump as possible. Hand-pick the root fragments out where ever you can find them in the soil. Discard everything that is dug up.
Boil 2-3 gallons of water and pour it into something that you can transport to the blackberry bush location. Carefully pour it over the entire area where you removed the plant from. Repeat this procedure throughout the day, four to six times in order to ensure that the roots don't and can't spread. Doing this helps waterlog any parts of the plant left, which will make it start to rot.
Use a rake over the area after you have boiled up the rest of the plant. This will get rid of any root fragments and rhizomes by unearthing them for you to discard of. Repeat this procedure multiple times over the course of a couple days.