Blackberry plants are a fruiting vine that grows in the wild and in domestic settings. In a wild state, blackberries self-propagate from underground roots, running suckers, and canes that drape to the ground and put out new roots. Domestic blackberries propagate willingly with low failure rates. When severed from the plant, cuttings from the stem and root will rapidly develop new plants. Take and plant root and stem cuttings in the late fall after the harvest season.
Propagation from Stem Cuttings
Cut a firm, green, leafy cane from the mother plant. Using a sharp pair of shears, cut the cane into 4 to 6 inch sections. Each section should have at least one set of leaves on it.
Fill a pot with a damp mixture of equal parts perlite and peat moss. Roll the ends of the cuttings in hormone rooting powder to stimulate root growth. Stick the bottom 2 inches of each cutting into the damp peat mixture.
Place the cuttings in a humid greenhouse or a warm, protected area. Mist the leaves and soil with water every day to keep the cuttings damp. Keep the soil in the pot damp but not saturated. Transplant the cuttings into the field after six weeks.
Propagating from Root Cuttings
Dig up the roots of a mature blackberry plant that you want to propagate. Brush the soil away from the roots until they are exposed.
Using a sharp pair of pruning shears, remove roots that are 1/4 to 1/2 inch round from the root ball. Cut these pieces of root into 6-inch long sections and set aside.
Plant the root sections 2 to 4 inches deep in the field or in a pot filled with potting soil. When planting in the field, space the root cuttings 2 to 5 feet apart.
Keep potted roots damp with light, weekly watering. When planting roots directly outside, winter precipitation should keep the area sufficiently moist. Water only if the weather is particularly dry.