Supporting raspberry plants with a structure transforms a sprawling patch into an organized and productive system. Trellising keeps the canes upright, which significantly improves air circulation around the foliage and fruit, reducing fungal diseases. This support ensures sunlight reaches all parts of the plant, promoting robust growth and fruit development. An organized system also simplifies harvesting and maintenance, preventing canes from drooping and fruit spoilage.
Selecting the Best Trellis Design
The appropriate trellis design depends on the type of raspberry cultivated: summer-bearing (floricane) or everbearing (primocane). Summer-bearing raspberries produce fruit on second-year growth, meaning new and fruiting canes coexist. For these, a simple post-and-wire system is highly effective, using a single or double wire to contain and support the mature floricanes. This design simplifies the annual pruning cycle after harvest.
Everbearing raspberries fruit on the tips of the current season’s growth (primocanes) and may benefit from a T-bar or V-trellis. These designs spread the canes laterally, maximizing sun exposure and allowing easier access to the fruit. The T-bar system involves cross-arms attached to posts, holding two parallel wires that create a narrow corridor for the primocanes. These systems offer superior management of vigorous everbearing varieties, keeping the heavy fruit load off the ground.
Necessary Materials and Site Preparation
For the simple post-and-wire trellis, you need two strong end posts, preferably 8-foot 4×4-inch pressure-treated lumber or sturdy metal posts. Use 12.5-gauge high-tensile galvanized wire, which resists stretching and corrosion. Specialized hardware is necessary for tensioning and anchoring the wire, including eye bolts, nuts, washers, and turnbuckles.
Site preparation starts by measuring the row length to determine the amount of wire and post spacing. End posts should be spaced no more than 40 feet apart to ensure proper wire tensioning. Mark the locations for the two end posts and any necessary line posts, which provide intermediate support for longer rows. Gathering tools like a post-hole digger, level, measuring tape, and wire tensioning tool before starting will streamline construction.
Building Your Raspberry Trellis
Setting the End Posts
Construction begins with securely setting the two end posts, which must bear the entire lateral tension of the wires. Dig post holes at least 2 feet deep, ensuring approximately 6 feet of the post remains above ground level. Setting the posts in concrete is highly recommended to prevent leaning when the wire is tensioned. Alternatively, thoroughly tamping the soil back into the hole in layers can provide stability for shorter rows. Use a level to confirm the posts are perfectly vertical before the concrete cures or the soil is compacted.
Installing Hardware
Once the end posts are secure, install the hardware to anchor and tension the wire. Drill holes completely through the end posts at the desired wire height, typically 3 to 4 feet above the soil line for the lower wire and 5 to 6 feet for the upper wire. Insert a long eye bolt through the hole, securing it on the inside face of the post with a washer and a nut, leaving the eye facing outward. This eye serves as the attachment point for the turnbuckle and prevents the wood from splitting under pressure.
Running the Wire
Attach the high-tensile wire to one end post, usually by connecting it to a turnbuckle already attached to the eye bolt. Run the wire down the length of the row, passing it through any line posts you have installed. Secure the wire to line posts with fence staples, ensuring the staples allow the wire to slide slightly. This ensures that only the end posts receive the full tension load.
Tensioning the Wire
At the second end post, attach the wire to the second turnbuckle, which is secured to the corresponding eye bolt. Use the turnbuckle to slowly tighten the wire until it is taut, removing any visible sag. Avoid excessive tension that could pull the end posts inward. A well-tensioned wire provides firm, continuous support necessary for managing the weight of mature canes and fruit. A specialized wire crimping tool may be needed to create secure loops when attaching the wire ends to the turnbuckles.
Training and Tying Raspberry Canes
Once the trellis is complete, integrate the raspberry canes with the support system. Training aims to keep the fruiting wood confined between the wires, maximizing light exposure and maintaining an organized row. For floricane varieties, new primocanes grow until the following season, while older, fruiting floricanes are gently tied to the wires using soft materials like twine or specialized plant ties.
Space canes approximately 4 to 6 inches apart along the wire to prevent overcrowding and promote air circulation. To tie a cane, loop the twine around the wire and then around the cane in a loose figure-eight pattern. This prevents the tie from chafing the stem as it grows. For T-bar or V-trellis designs, canes are often woven between the parallel wires, which naturally keeps them upright without individual ties.