Propagating your blackberries ensures healthier plants and more berries for the next seasons. Blackberries are most commonly propagated by a process called tip layering. Blackberry bushes naturally take root whenever their stems touch soil, and tip layering takes advantage of this natural characteristic. This is the easiest and safest manner of propagation for home gardeners. The new plant grows easily and quickly, still attached to the parent plant until it finally establishes itself. Once the new plant is established, the attachment is severed, leaving the gardener with two healthy bushes.
Look over your blackberry bush, and find a stem that is in the best condition. It must have no blemishes or dead material growing from it. Typically, your tallest or longest stem with the best production is the right one to choose.
Stretch the stem towards the ground. The stem should be in a relaxed stretch. It does not matter how far away the stem is from the plant because the new plant that will be produced will be re-planted in a different area.
Dig a small, 6-inch hole, and bury the tip of stretched stem in the hole. The weight of the soil should hold the stem down; however, attaching the stem to the ground with twine will ensure the stem does not spring back up.
Water the area until the ground is moist, and add a small layer of mulch to help retain moisture. Make sure the area is always moist, watering when needed for 2 to 3 months.
Sever the parent stem from the new plant after 2 to 3 months when a new plant has emerged from the soil. Cut the parent stem so that 12 inches of the original stem is left to the new plant.
Dig up the new plant at the roots, and move it to its permanent location. Blackberries thrive best in full sun.