Prune pyracantha during the spring after it finishes blooming. Remove any dead or diseased wood at its point of origin. To maintain shape, select wayward or leggy side shoots and cut them back to the first three leaves or cluster of berries. Remove lower branches for a treelike form or leave them in place for a more natural shape. Dispose of the plant tissue, either in the trash or in compost. Pyracantha has sharp thorns, so wear thick gloves while pruning to avoid injuries. Disinfect your pruning shears before making any cuts in a container filled with 1 part bleach and 9 parts water. Let the shears soak for 5 minutes. Rinse them with water and allow them to air dry.