Blackberry plants are popular for their sweet fruit and relatively easy care. Increasing their number through propagation is a straightforward process, but success depends heavily on timing the method to align with the plant’s natural growth cycle. Choosing the correct season for each method allows gardeners to efficiently increase their yield, replace older canes, or expand their planting area.
Dormant Season Propagation: Root Cuttings and Division
The period of winter dormancy, specifically late winter or very early spring before new leaf buds begin to swell, offers the ideal window for propagating blackberries using their root system. Working with the plant during this resting phase minimizes shock and increases the likelihood of successful establishment in a new location. This timing is particularly effective for many common erect and semi-erect blackberry varieties that naturally produce suckers from their roots.
Root cuttings are harvested from established plants while they are dormant, usually in late fall or winter. Sections of root, typically 2 to 6 inches long, are carefully collected. These pieces can be stored in cold conditions, such as a refrigerator, for several weeks to simulate the necessary chilling period. For planting, the root sections are laid horizontally or inserted vertically into a moist, well-draining medium.
Division involves physically separating older, established blackberry clumps that have grown dense into smaller, independent plants. This process reduces overcrowding and provides new, healthy plants for transplanting elsewhere. Establishing new plants using root material during dormancy significantly reduces transplant stress, as the plant is not simultaneously supporting above-ground growth.
Active Growth Propagation: Softwood Cuttings
Softwood cuttings are taken during the active growing season, typically from late spring to mid-summer (May to July). This period is chosen because the new canes are still tender and flexible but have begun to firm up slightly. The timing is crucial: the cane must be succulent enough to root easily but not so green that it wilts immediately upon cutting.
To create a new plant, a 4 to 6-inch section is taken from a non-fruiting cane that grew that season, making a clean cut. The lower leaves are removed, and the base of the cutting is often dipped in a rooting hormone to encourage root formation. The prepared cutting is then placed into a moist, porous potting mix.
Softwood cuttings require a high level of humidity to survive until new roots form. Cuttings must be misted frequently or placed in a propagation chamber or cold frame to prevent the foliage from drying out. New roots can begin to develop within three to four weeks, allowing the new plant to be potted up or transplanted later in the season or the following spring.
Late Summer Propagation: Tip Layering
Tip layering is especially effective for trailing varieties whose long canes naturally arch toward the ground. The optimal timing is mid to late summer (August or September), when the current season’s canes have achieved significant length. This technique capitalizes on the plant’s tendency to root where a cane tip touches the soil.
The process involves gently bending the tip of a long, healthy cane down and burying the last few inches into the soil. The buried section should be secured with a small rock or wire to ensure constant contact with the moist earth. Once buried, the tip will begin to form roots, often within a few weeks, while still attached to the mother plant.
The new plantlet should be left attached to the parent plant throughout the fall and winter to allow the root system to fully develop and strengthen. The following spring, while the plant is still dormant, the cane connecting the new plant to the mother plant is severed. This newly independent plant, now with a robust root system, can then be successfully transplanted to its permanent location.