Raspberry canes grow tall and heavy with fruit, making them susceptible to bending, breaking, or sprawling across the ground without adequate support. A proper support system, or trellis, is necessary to keep the canes upright. This prevents fruit from touching the soil and reduces the risk of fungal diseases by improving air circulation around the foliage and fruit. Supporting the canes also organizes the row, making it easier to access the fruit for harvesting and to manage the annual pruning cycle, ultimately leading to higher yields and healthier plants.
Identifying Raspberry Growth Habits
The ideal support structure for raspberries depends directly on the plant’s unique biennial growth cycle and whether the variety is summer-bearing or everbearing. Raspberry canes live for two years, with new canes emerging each spring. These young, first-year canes are known as primocanes. Summer-bearing varieties produce fruit exclusively on the second-year canes, called floricanes, typically in the mid-summer. Once the floricane has fruited, it dies back and must be removed, but the remaining primocanes will become the next season’s floricanes, requiring support for their full two-year lifespan. Everbearing, or fall-bearing, varieties produce a crop on the tips of the primocanes in the late summer or fall of their first year. Many growers opt to cut all primocanes to the ground after the fall harvest to focus the plant’s energy on a single, heavier fall crop, simplifying the need for complex, long-term support.
The Post and Wire Hedge System
The post and wire hedge system, sometimes called an I-trellis, is a simple and cost-effective method used primarily to contain primocane-fruiting varieties or smaller plantings. This design works by corralling the canes into a narrow, vertical hedge rather than providing individual cane support. The system requires two sturdy end posts and intermediate line posts spaced roughly 15 to 30 feet apart, depending on the row length.
To construct this system, the posts should be eight feet long and buried about two feet into the ground. They are fitted with two parallel wires or lengths of heavy twine on either side of the row. The lower wire is typically positioned about three feet off the ground, and the upper wire is placed around five feet high. The canes simply grow up between these two sets of wires, which prevents them from flopping outward under the weight of the fruit or due to wind. For stability, the end posts should be anchored or braced to withstand the tension of the wires pulling inward.
The wires or twine should be secured tautly to the posts using staples, eye hooks, or tensioning hardware to form a two-foot-wide channel that restricts the width of the raspberry row. This basic containment method improves harvesting and air circulation. As the canes grow, they are simply tucked back inside the wires to keep the row tidy and upright.
Building a T-Trellis or V-Trellis
The T-trellis and V-trellis designs offer more structured, long-term support, which is often preferred for summer-bearing varieties or for any planting where maximizing air flow and fruit exposure is a priority. Both systems use 4×4 or similar treated lumber posts set deep into the ground, generally eight feet long with two to three feet buried for stability.
The T-trellis features a horizontal cross-arm attached to the top of the upright post, resembling a capital ‘T’. The cross-arm, often made from a 2×4, can range from 24 to 36 inches wide, with two to three wires strung parallel along the length of the row, connecting the ends of the cross-arms on each post. This configuration spreads the canes outward, preventing excessive crowding and ensuring better light penetration and air movement through the canopy.
The V-trellis is a variation that uses pairs of posts or angled cross-arms that widen toward the top, creating a distinct “V” shape in the row. The V-trellis is particularly effective for separating the fruiting floricanes from the new primocanes, as the older canes are trained to the outer wires of the ‘V’, leaving the center open for new growth. The posts for a V-trellis are typically set 20 to 30 degrees from vertical, with the base of the posts closer together than the top. Both the T and V systems facilitate easier harvest because the fruit is held away from the center of the row, and they reduce disease pressure by minimizing humidity within the thick growth.
Post-Installation Maintenance
Once the support system is built, the process of training the raspberry canes begins and continues throughout the growing season. New primocanes emerging in the spring should be gently guided toward the support wires as they elongate, especially those destined to be the next season’s floricanes. This training involves loosely tying the canes to the wires using soft material like cotton twine or fabric strips, or simply tucking them between the parallel wires of the hedge system.
The support structure also aids in thinning, which is necessary to prevent overcrowding and promote the growth of strong, productive canes. For established rows, the goal is to maintain a density of approximately four to five of the largest canes per linear foot of row, with weaker or damaged canes removed at the base.
The wires themselves may require annual adjustment. High-tensile wire is often used and can be tightened with turnbuckles or similar hardware to maintain the necessary tension, especially after a winter of heavy ice or wind load.