Thornless blackberries (a type of Rubus species) are a favored choice for home gardeners because they offer large, sweet fruit without the painful harvesting experience of their thorny relatives. These varieties, bred specifically for easier management, still require careful planning to ensure optimal growth and maximum fruit production. Establishing the correct distance between plants is the first step in creating a productive, low-maintenance berry patch. Proper spacing directly influences air circulation and light exposure, which are the main factors in preventing common fungal diseases and maximizing yield.
Preparing the Planting Site
Blackberries thrive in locations that receive a minimum of six to eight hours of direct sunlight each day. Insufficient light will lead to weak canes and significantly reduced fruit quality and quantity. Before planting, conduct a soil test to determine its composition and pH level. Blackberries perform best in slightly acidic soil, ideally with a pH range between 5.5 and 6.5.
If the soil test indicates a pH outside this optimal range, amendments such as agricultural lime can be incorporated to raise the pH, or soil sulfur can be used to lower it. The soil must offer excellent drainage, as blackberries are susceptible to root rot in waterlogged conditions. If the existing soil is heavy clay, planting in raised beds (10 to 12 inches high) enriched with organic matter will significantly improve drainage and root health. Clearing the planting area of any perennial weeds or grasses should be completed well in advance. These competitors steal moisture and nutrients from the newly planted roots, hindering establishment.
Spacing Requirements for Optimal Growth
Spacing depends heavily on the growth habit of the specific thornless variety chosen. Thornless blackberries fall into two main categories: erect/semi-erect and trailing. Erect varieties, such as ‘Navaho’ or ‘Arapaho’, have stiff canes that stand relatively upright, though they still benefit from support. These plants require a spacing of approximately three to five feet between plants within the row.
Trailing varieties, including ‘Black Satin’ or ‘Marion’, produce long, pliable canes that must be trained onto a trellis system. Because these varieties are more vigorous and spread out horizontally, they need significantly wider spacing, typically five to eight feet between plants in the row. Planting too closely restricts air movement around the leaves and canes, which creates a humid microclimate that encourages the development of fungal diseases like cane blight. Conversely, planting too far apart wastes garden space and reduces the overall yield per linear foot of row.
Row spacing is as important as in-row spacing and should be determined by the type of equipment or walkway needed. For home gardens, rows should be spaced six to eight feet apart to ensure adequate room for harvesting, pruning, and air circulation. Commercial operations often increase this distance to 10 or 12 feet to accommodate machinery. This space allows sunlight to reach the lower portions of the canes, promoting fruit development across the entire plant canopy.
Designing and Installing Support Systems
Nearly all thornless blackberry varieties require trellising to manage long canes and support a heavy fruit load. Erect and semi-erect types benefit from trellising to prevent flopping, while trailing types absolutely require it. Trellis systems keep the fruit off the ground, improving cleanliness and accessibility for harvest, and optimizing light exposure.
The T-trellis is a popular system, consisting of sturdy posts placed along the row with horizontal cross-arms attached near the top. For a standard T-trellis, posts are set 15 to 25 feet apart, with the cross-arms often being 30 to 36 inches wide. Two or more parallel wires are then strung between the cross-arms, creating a wide support structure where the canes can be tied or woven. This design is highly effective for containing the growth of semi-erect varieties.
A more advanced system is the V-trellis, which uses pairs of angled posts or wires that open up the canopy into a “V” shape. This design physically separates the fruiting canes from the new vegetative growth. By keeping the fruiting canes on the outer wires and the new growth up the center, the V-trellis maximizes light penetration and significantly improves air circulation, reducing disease risk. The posts for a V-trellis are generally set 25 to 35 feet apart down the row, keeping the canes within the planned row width.
Managing Canes Through Pruning
Pruning is an annual practice that ensures the blackberry patch remains productive and contained within the established spacing and trellis system. Blackberries have a biennial cane structure, meaning that individual canes live for two seasons. Primocanes emerge in the first year and produce no fruit, while floricanes are second-year canes that bear fruit and then die shortly after harvest.
Tipping Primocanes
The initial pruning technique involves tipping or heading back the new primocanes when they reach a height of three to four feet, depending on the variety. This action removes the cane’s growing tip, which encourages the development of lateral branches that spread horizontally to fill the trellis space. This horizontal branching increases the overall fruiting surface area for the following year’s harvest.
Removing Floricanes
The second primary pruning task involves removing the dead floricanes immediately after harvest concludes. Cutting these old, spent canes back to the ground prevents them from becoming a source of disease for the new primocanes.
Thinning New Canes
Thinning the new primocanes during the dormant season is necessary to maintain productivity and health. Growers should select only the strongest, healthiest new canes, leaving three to five canes per linear foot of row. This thinning process prevents overcrowding, ensuring that the remaining canes receive sufficient light and air for robust fruit production.