Propagation techniques for blackberries:
Tip layering is used on most brambles (blackberries, black and purple raspberries). In mid to late summer the cane tips arch over and leaves at the end become small and curled. This is the proper time for tip layering. Cut a slit in the soil 2 to 4 inches deep using a trowel or spade. Insert the tip of the cane about 2 inches into the soil and close the soil around the tip by stepping on the soil. The tip will root and form a new plant by fall. New plants can be cut from the parent, dug and replanted in fall or early the next spring. Suckers from around the base of the plant can be dug and replanted to propagate thorny blackberries in the spring. Root cuttings can be dug from the base of thorny blackberries. Cuttings that are pencil thickness in diameter and 3 inches long can be planted two inches deep in the spring and will produce new plants. However, this technique requires patience and persistent weed control, since it often takes 2 months for the new shoots to push out of the ground. Vigorously growing blackberry primocane shoot cuttings from any of the blackberry types may be rooted under a mist system to propagate plants. However, this technique is a little more difficult for most home growers.