Raspberries produce long, woody stems called canes that can become tall and unruly. While they can technically grow without intervention, providing a structural system is highly beneficial for the plant’s health and ease of management. The decision to install a trellis, and the type needed, depends on the specific variety of raspberry being grown and the grower’s goal for the harvest.
Why Support Structures Are Necessary
Holding raspberry canes upright significantly improves plant health and productivity. Fruit-laden canes often become top-heavy, causing them to bend or sprawl onto the ground. Contact with the soil exposes the developing fruit to moisture, increasing the risk of rot and inviting pests. A well-designed support system addresses this by elevating the canes, which facilitates improved air circulation throughout the plant canopy. Increased airflow helps to dry the leaves and fruit quickly after rain or morning dew, reducing the incidence of fungal diseases like Botrytis fruit rot. Upright canes also ensure that sunlight can penetrate deeper into the plant structure, promoting more uniform ripening and maximizing the total fruit yield. Additionally, corralling the canes makes harvesting much easier, as the fruit is easier to spot and pick without navigating a dense, thorny tangle.
How Raspberry Variety Dictates Support Needs
The need for structural support is linked to the two biological growth patterns found in cultivated raspberries. These patterns are defined by the cane’s fruiting cycle, which determines its height, weight, and lifespan. Understanding this difference is the most important factor in deciding on a support system.
The first group includes floricane-fruiting varieties, often called summer-bearing raspberries, which produce fruit on second-year canes. These canes, which are vegetative in their first year (primocanes), grow up to eight feet and become woody before producing a single crop in their second year (floricane). Because floricanes must overwinter and carry a substantial load of fruit, they are heavier and require a substantial, permanent trellising system for stability.
The second group is primocane-fruiting varieties, commonly known as fall-bearing or ever-bearing raspberries, which produce fruit on the tips of the first-year canes. When grown for a single fall crop, these canes are typically cut back to the ground each winter. This annual pruning cycle eliminates the need for a complex, permanent support structure, as the shorter, single-season canes can often be managed with minimal support. If a grower chooses to “double-crop” these varieties for both a fall and a summer harvest, the canes will be managed similarly to floricanes and will then require robust support.
Common Trellis Systems for Raspberry Canes
For gardeners who determine their raspberries require substantial support, several proven trellis systems offer effective cane management.
Post and Wire System (I-Trellis)
The simplest and most common design is the Post and Wire System, sometimes called an I-Trellis, which is effective for long rows of summer-bearing varieties. This system uses sturdy wooden or metal posts, typically sunk two feet into the ground with five to six feet remaining above the soil line, spaced 20 to 30 feet apart. Two to three galvanized wires, such as a 12.5-gauge high-tensile wire, are run horizontally between the posts at different heights, often around three and five feet from the ground. Canes are tied to these wires or loosely woven between them for support.
V-Trellis and T-Trellis
The V-Trellis is useful for separating the new and old canes in a double-cropping or floricane system. This structure is built using two parallel posts set at an angle 20 to 30 degrees from vertical, creating a “V” shape down the row. The V-Trellis allows the second-year fruiting floricanes to be tied to the outer wires, while the new first-year primocanes grow freely up the center of the “V.” This separation significantly improves light exposure and air movement for both generations of canes, which helps to increase overall yield and reduces the spread of disease. A similar variation, the T-Trellis, uses a horizontal cross-arm at the top of a single post to spread the wires and create an open canopy.
Alternative Methods for Cane Management
Not all raspberry plantings require the construction of a permanent, high-tension wire trellis. For many primocane-fruiting varieties, the management approach known as the Hedge Row System offers a simpler alternative. This method relies on the grower pruning all canes down to the ground during the dormant season, typically late winter or early spring. Since these canes only produce fruit on their tips during the late summer and fall of their first year, this annual pruning eliminates the need for complex vertical support. The resulting shorter canes can be managed with a simple corral system. This involves installing short posts at the ends of the row and running heavy twine or lightweight wire on either side of the row at heights of two and four feet. This technique effectively keeps the canes from sprawling into the pathways, without individually tying each cane. This simplified maintenance is why many home growers select fall-bearing varieties.