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Vineyard Management The Topiary Trellis

There is no single configuration that fits all needs—but with a snip here and a snip there, any vine can bemade to fit any trellis.

By Gary Strachan O

ne of the cornerstones of sustainable vineyard management is to minimize labour input to the essentials. If this is done well, it can save money while improving yield and quality. If it’s done badly, non-intervention when the vineyard requires attention is a really bad idea.

Sometimes I feel like a broken record. The best quality in a vineyard is achieved from balanced growth. This is not to say that every time a cane juts out at a funny angle or exceeds the height of the upper catch wire, you pounce on it to prune the vine into submission. It’s easier to adapt your vineyard management to the natural growth habit of the vine than it is to force the vine into the shape of your trellis. There are dozens of trellis

configurations for good reason. There is no universal trellis that is optimal for all varieties, all soils, and all sites. You can use a vertical shoot position (VSP) to stimulate vigour and a hanging cane to suppress vigour. Facetiously, for everything else there is the topiary trellis. A snip here and a snip there and any vine can be made to fit any trellis. Look hard at how a grapevine grows in the wild, such as a vine that escaped from a vineyard or was allowed to grow wild in someone’s backyard Grape canes typically don’t lignify (harden) until fall, so they remain supple and compliant during their early summer growth phase. If the canes encounter a vertical surface, such as a tree trunk, tendrils assist the green canes to grip and grow upwards. Apical dominance mediated by auxin (a plant growth hormone) will stimulate the canes to grow upwards. So

Vines trained to a hanging cane system to compensate for a vigorous site.

long as the canes are supported they continue to grow upwards because gravity stimulates the release of auxin from the uppermost growing tip. When the cane grows beyond its support, such as beyond the canopy of a tree, the cane will eventually sag downward under its own weight. The effect of gravity then suppresses the secretion of auxin and the plant’s metabolism shifts toward ripening fruit and hardening canes. The metabolic shift to harden canes and ripen fruit is controlled via the interaction of a series of plant hormones whose change in balance can be triggered by (believe it or not) gravity, and to a lesser extent by temperature and the length of darkness overnight.

British Columbia FRUIT GROWER • Fall 2011

Anyone who has used a Scott Henry trellis should be familiar with this phenomenon. When the canes on the lower fruiting zone are dropped downward, cane elongation is visibly suppressed by comparison with canes growing upward from the upper fruiting zone. This situation imparts an interesting level of control to the vineyard manager. If you want to stimulate cane elongation, maintain the canes in a vertical position. If you want to suppress cane elongation, let the canes droop or train them downward. There is also the interesting

phenomenon of what happens when the vine is topped and the green cane’s growing point is removed. Where did all

23 Vines trained to a vertical shoot position (VSP) with too much growth.

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