Raspberry canes are naturally long and arching, benefiting significantly from trellising, which provides vertical support to manage vigorous growth. This technique maximizes fruit production by ensuring better light penetration and air circulation throughout the canopy. Trellising prevents fruit-laden canes from breaking and keeps berries clean, protecting them from pests and diseases found on the soil. Organizing the canes also makes annual maintenance tasks like pruning and harvesting simpler and more efficient for the home gardener.
Selecting the Right Support System
Choosing a trellis design depends on the specific raspberry variety being cultivated. Raspberries are categorized into summer-bearing varieties (floricane-fruiting) and fall-bearing varieties (primocane-fruiting). Floricane types produce fruit on second-year canes (floricanes) and require a robust, permanent system because both the fruiting floricanes and new primocanes need simultaneous support.
A simple post-and-wire system, often called a single-wire trellis, is suitable for most types, especially in smaller gardens, using one or two parallel wires. For dense, higher-yielding floricane varieties, the V-trellis is a better option. This design uses posts angled outward to form a V-shape, allowing fruiting canes to be tied to the outer wires while new primocanes grow in the center. Primocane varieties, often cut down each winter for a single fall crop, can use a less complex T-trellis or a simple removable two-wire system to prevent canes from flopping over during harvest.
Installing the Trellis Structure
The standard post-and-wire system starts by setting sturdy end posts to anchor the structure. Use posts six to eight feet long, setting them two to three feet deep into the soil, often with concrete, to resist the tension of the wire and the weight of mature canes. End posts should be fifteen to twenty feet apart, with line posts placed every twenty to thirty feet to prevent wire sagging in longer rows.
Once posts are secured, support wires are attached at strategic heights using hardware like eye bolts or wire vice anchors. For a two-wire system, the lower wire is strung about eighteen inches from the ground, and the upper wire is placed near the top, approximately five feet high. Use 11- or 12-gauge galvanized or high-tensile wire for strength and rust resistance. The wire must be properly tensioned using turnbuckles or specialized anchors to ensure it remains taut, providing firm support against wind and the heavy fruit load.
Training and Initial Cane Management
The process of training canes onto the new trellis begins once the new primocanes have reached a height of about thirty to thirty-six inches. For a simple post-and-wire system, the goal is to keep the canes confined within the boundaries established by the wires, often referred to as a hedgerow. As the canes grow taller, they are gently tucked between the parallel wires or tied individually to the wire using soft garden twine or cloth strips, preventing them from sprawling into the pathways.
Thinning new cane growth is an important and continuous management task performed alongside training to ensure optimal plant health. Early in the season, remove all but the strongest canes, aiming for a final density of three to five canes per linear foot of row, or spacing them about six inches apart. This aggressive thinning prevents overcrowding, which contributes to poor air circulation and fungal diseases like powdery mildew. Proper training and thinning ensures remaining canes receive ample sunlight, necessary for high-quality fruit production and strong overwintering buds.
Seasonal Pruning and Renewal
Trellising clarifies the annual pruning regimen by visually separating canes based on their age and fruiting status. For summer-bearing (floricane) raspberries, the canes that have finished fruiting must be removed entirely to ground level immediately after the summer harvest. These spent canes are easy to identify because they are woody and often have dried fruit clusters. Removing them promptly redirects the plant’s energy toward strengthening the new primocanes that will bear fruit the following year.
The remaining first-year primocanes, supported by the trellis, are then thinned and left to overwinter. For fall-bearing (primocane) raspberries, pruning depends on whether the grower wants one or two crops. To produce a single, large fall harvest, all canes are cut down to the ground during late winter dormancy, allowing new canes to emerge in spring. If a smaller summer crop is desired, the fruited tips of the primocanes are cut off, and the remaining lower sections are left on the trellis to produce an early summer crop before being removed completely.