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In the Vineyard

While you wait for the grapes to bloom...

Explosive growth during our warmspring brings need for some labour intensive canopy management.

By Gary Strachan M

ay is usually kind of quiet in the vineyard. Pruning and tying is done. Tractor and sprayer are serviced. Mow the grass. It’s the time to sucker the trunks before the shoots harden. Enjoy the warm spring sun, not too hot.

Depending on your soil’s water holding capacity, you may or may not have to get irrigation underway. If it’s cool enough, you may be able to get away without spraying for mildew. It’s usually too early to worry about a Botrytis spray because grapes won’t bloom for another few weeks. This year was different. April was hot. Grapes burst onto the scene with a vengeance. Some vineyards had a metre of growth by the end of May and were coming into bloom weeks early. Canopies were already heavy and dense by the end of May. It’s time for a lot of hand labour.

With this much growth early in the season, it’s a good idea to combine several operations into a single pass, but be aware that this will almost certainly be more time-consuming than in previous years.

The first step is to assess the overall vigour of the vineyard. Are the internodes exceptionally long? Say, greater than 10 or 12 cm? Is this just a normal growth rate for your site because your soil has high water holding capacity?

If not, then perhaps you’re over- irrigating. If your internodes are in the 5

28 British Columbia FRUIT GROWER • Summer 2016

to 6 cm range in spite of the warm early spring weather, then look for a reason such as winter injury, low fertility, or water stress.

If your canopy is too dense, you may have to shoot-thin. The usual rule is that there should be no more than two layers of leaves in the canopy, but at this early stage it may be difficult to determine how many layers are present. Shoot spacing helps to minimize shading. I aim

for about 12 to 15 shoots per metre of row, independent of plant spacing. Shaded leaves in the third layer are essentially parasitic to the vine because they use more energy for their respiration than they contribute from photosynthesis. Berry composition from a vineyard with a dense canopy typically

Pre-bloom grape cluster.

has high potassium and causes winemaking problems related to high pH such as excessive oxidation, loss of varietal character, and high requirement for sulphur dioxide to stabilize the wine.

At this writing, I don’t know how good the fruit set will be, but I expect it will be strong. The shoots have pushed

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