Grape vines have an aggressive, sprawling growth habit that requires structural management to ensure productive fruit development. A sturdy support structure, known as a trellis, manages the vine’s vigor and prevents it from becoming an unproductive, tangled bush. By holding the canopy upright and open, a trellis maximizes the leaves’ exposure to sunlight, which is tied to the vine’s ability to produce high-quality sugars for fruit. Lifting the foliage and separating the leaves improves air circulation, reducing the localized humidity that encourages fungal diseases like powdery mildew. A well-built system concentrates the vine’s energy into fruit production, making vineyard management and harvesting more efficient.
Selecting the Best Support Structure
The choice of support system depends on the grower’s space, budget, and ultimate goal for the grapes. A Vertical Trellis system, such as Vertical Shoot Positioning (VSP) or T-Trellis, is the most practical choice for maximizing fruit yield in compact spaces. The VSP system trains the canopy vertically along multiple parallel wires, which is ideal for uniform sun exposure and is the standard in commercial viticulture. For aesthetic purposes or home gardens, a Head Training system (Goblet or Wagon Wheel) uses a single, short post to support a self-standing vine, requiring intensive pruning but no extensive wire work. Arbors and Pergolas are horizontal overhead systems that create a shaded canopy, working well for table grapes and decorative landscaping where high production density is not the primary concern.
Essential Materials and Tools
A robust wire trellis requires commercial-grade materials designed to withstand the immense weight of a mature vine.
Materials
- 8- to 10-foot long end posts made of pressure-treated wood or galvanized steel.
- 7-foot line posts to place between the ends.
- High-tensile, 9- to 12.5-gauge galvanized wire for tensioned lines.
- Wire tensioners (turnbuckles or Gripples) and eye bolts or wire vises for anchoring the wire to the end posts.
Tools
Necessary tools include a post hole digger or auger for setting posts, a level, a heavy sledgehammer for driving line posts, and a crimping tool for securing the wire hardware.
Step-by-Step Construction Guide
The first step is laying out the design and marking the precise locations for the end posts and intermediate line posts. End posts are typically spaced 50 to 100 feet apart, with line posts placed every 12 to 25 feet along the row.
Setting the end posts is the most important part of the process, as they bear the full tension load of the wires and the weight of the mature crop. These posts must be buried 3 to 4 feet deep, stabilized with concrete at the base, and braced to prevent leaning inward under tension. Bracing is achieved using an H-brace assembly or a screw-in earth anchor. The H-brace uses a second post set a few feet away with a horizontal cross member and a diagonal wire to transfer tension deep into the ground.
Once the posts are secured, hardware must be attached at predetermined heights for the wires (e.g., 3 feet, 4.5 feet, and 6 feet for a multi-wire system). Eye bolts or specialized trellis brackets are secured to the end posts. U-shaped staples are gently hammered into the line posts, but they should not be driven completely flush. This allows the wire to move freely to accommodate seasonal expansion and contraction.
Stringing the high-tensile wire begins by securely anchoring one end to the end post’s hardware using a crimped loop. The wire is then unspooled along the row, threaded through the staples on all line posts, and attached to a tensioning device on the opposite end post. The wire should be tightened to approximately 250 pounds of tension, which removes all sag without risking the post bracing. This tension must be periodically checked and adjusted, often relaxed during the coldest winter months when the metal wire naturally contracts.
Training and Initial Vine Attachment
Once the physical structure is complete, the young grapevine must be integrated with its permanent support system. The goal in the first year is to establish a single, straight trunk that reaches the lowest wire or the planned height of the permanent cordon. After planting, select the strongest shoot to become the future trunk, immediately pruning away all other shoots to direct the plant’s energy into this one cane.
The chosen shoot should be loosely tied to a vertical training stake, such as rebar or bamboo, which is secured to the trellis wire. Use soft material like elastic tape or loose twine for tying every 12 to 18 inches, ensuring the ties do not constrict the rapidly thickening trunk. As the cane grows, it is guided straight up the stake toward the lowest permanent wire, which will become the foundation for the permanent woody arms, known as cordons, in subsequent years. Any emerging flower clusters on a young vine should be removed to ensure the plant focuses its resources on developing a strong root system and a sturdy trunk.