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Section 14: Trellises

Muscadine single wire trellises normally have the wire 5 feet about the ground.The 5 foot trellis has been the most popular with Georgia growers since it allows for better air circulation that shorter trellises.

Trellis construction is the most expensive step in establishing a muscadine grape vineyard. Since the trellis is relatively permanent, it should be strong enough to support a heavy crop and made of durable materials that will last for many years. All wood products used in the vineyard should be pressure treated with wood preservatives (or of a specially durable wood type you know will last in your area).

In sizeable plantings where mechanical harvesters and pruners will be used, the one-wire trellis is recommended. Most experienced growers prefer the one wire trellis because of ease of establishment, pruning, harvesting, and renovation. Since row widths are such that vineyard machinery can move only in one direction at a time, without room to turn around, extremely long rows should be avoided. If the vineyard site is best suited to long rows, break the rows into sections 400 to 600 feet long, leaving a gap 30 feet wide for convenience of movement through the vineyard. A span of 600 feet is also the maximum safe stress load for No.9 wire.

One-Wire Trellis End posts should be at least 5 inches in diameter and 8 feet long. Set the end posts 3 feet in the ground so the trellis wire will be 5 feet high. End posts holes can be dug with an auger or post hole. End posts can also be set with a post driver. Several different bracing systems can be used.

Figure 2. The One-Wire Trellis System for Growing Muscadines

Figure 3: “H” bracing

“H” bracing (Figure 3) involves setting a 4 to 5 inch post 8 feet long, 3 feet deep, and 6 feet from the outside brace post. Then position a 4 inch x 4 inch pressure treated timber or 4 inch post between the tops of the two posts (horizontal beam). Run a double 9 gauge wire from the top of the inside post to the bottom of the outside post. Twist the wire with a “twitch stick” to tighten and secure the brace system. It is very important that the top horizontal beam be longer than the vertical post for this system to work properly and not “fold up.”

Photo 14.1: The One-Wire Trellis System for growing muscadines. A missing vine allows the ‘H’ bracing to be viewed.

Photo 14.2: Poorly constructed ‘H’ bracing. The wood is not durable enough and horizontal beam is too short.

Deadman bracing (Figure 4) involves setting the end post angled slightly away from the vineyard. Two strands of 9 gauge wire are run from the top of the post to a deadman buried four feet from the base of the post and four feet deep. A number of different materials have been used successfully for the deadman. Screw-in mobile home anchors,metal plates welded to steel shanks, concrete dead-men attached to a steel shank, sections of old railroad ties, sections of old posts buried horizontally, and sections of old pipe have all been used successfully.

Figure 4. The deadman anchoring system. Note how the end post is sloped back slightly.

Wooden line posts, 3 to 4 inches in diameter and 7 feet long, should be set so that the wire will be 5 feet high.Usually the line posts are set 2 feet deep.However, growers on “tight” soil sometimes set 6.5 foot posts 1.5 feet deep with good results. Spacing on the line posts is typically 20 feet. Line posts holes can be dug with an auger or post hole digger.If a good job subsoiling is done, the soil will be very soft in the row and easily excavated with a post hole digger.

Wire. Use number 9 galvanized wire or 12.5 gauge high-tensile fence wire.High-tensile strength wire is more difficult to handle than than number 9 wire. Start by wrapping the wire around the upper part of the end post, then stapling it to the side of the end post. Bring the wire up and put another staple in it on the side of the post before going over the top of the end post. Staple the wire to the top of the post with 2 ½ inch “pole barn” staple. Leave the top staple loose enough so that the wire is not held rigidly. If the wire is bound too tightly by the staple, it may break when tightened. At the other end of the trellis, staple the wire loosely to the top of the end post.Tighten the wire with a fence stainer or claw hammer, then hammer the end staple down just enough to hold the wire from slipping. Put a second staple in the side of the post just below the top. Wrap the wire around the post several times and use a staple driven into the side of the post to hold the wire wrappings (Fig.5). Periodic tightening after pruning is needed as the wire stretches over the years. Fence stainers, available from livestock supply houses, can also be used at one end of the trellis for easy tightening. They have a rachet-type gear which tightens the wire.

Figure 5. A method of securing the end wire which is low cost and easy to accomplish.

Easy, low cost construction, pruning, and harvesting are the main advantages of the one-wire trellis. The major disadvantage is lower yields. The one-wire trellis yield is about two-thirds the Geneva Double Curtain yield.Despite the lower yields, most experienced muscadine growers prefer the single wire trellis.

Figure 6 . A young vineyard being trained to the Geneva Double Curtain Trellis System.

Geneva Double Curtain Trellis: The Geneva Double Curtain (GC) trellis (Figure 6) developed in New York to train vigorous grapevines, has proven to be a high yielding trellis system. It is especially suited to mechanical harvesting and capitalizes on the vigor of muscadines by providing 28-40 feet of fruiting arm per vine.

Figure 7. Details for constructing the Geneva Double Curtain Trellis

The line posts, which are typically 3 to 4 inches in diameter and 8 feet long, are placed 2 1/2 feet in the ground and 20 feet apart (Figure 7 ). The end brace post is 8 feet long with a minimum diameter of 5 inches. It is placed 4 feet in the ground and angled back slightly away from the row. A 6 1/2 foot post is used as an inside brace post. Place it 2 1/2 feet in the ground, 6 feet from the outside brace post and position a 4″ x 4″ timber between the top of the two posts as a brace. Run a double 9 gauge wire from the top of the inside brace post to the bottom of the outside brace post, and twist it to tighten the entire brace system.

The cross arms (supports) are rough sawn, pressure treated, No. 2 grade 2 x 4’s or equivalent. The supports are 29 inches long and are pre-drilled two inches from the end to accommodate a 3/8 x 8 inch galvanized bolt. An additional hole is pre-drilled from the other end of the support parallel to the ground to allow the 9 or 11 gauge brace wire to pass through. After passing the loop end of the double wire through the support, place a 3/4 inch washer over the loop and attach a chain repair link to the loop (Figures 8 ). The line wires run through these chain repair links. The brace wires are now fastened around the top of the post so the supports form a “Y.” Both should have approximate 35o angles with the ground and should measure 4 feet from tip to tip. Use nine gauge wire or 12.5 gauge high-tensile strength fence wire for the main wires. Both of these main wires are fastened to the top of the outside brace post, then threaded through a 45 inch spreader and run down either side of the trellis through chain repair links. The opposite end of the trellis is braced in the same way and the two wires tightened around the top of the outside brace post. The trellis wire will be 5 feet 9 inches above the ground using 8 foot line posts.

Pre-fabricated metal cross arms are also available (Figure 10). Although material costs for these cross arms are high, installation costs are reduced using pre-fabricated support. The pre-fabricated metal arms do not need a cross support brace wire between the metal arms, so set seven or eight foot line posts three feet in the ground. The wire should be 5 ½ feet off the ground for good air circulation.

Figure 8. Details of the Geneva Double Curtain Trellis System

 

Figure 9. A Geneva Double Curtain post using 2 x 4 support arms.

Figure 10. Pre-manufactured Geneva Double Curtain Trellis support arms in the vineyard.

Section 15: Training the Vines to the Trellis