Vineyard Management
Roller coaster ride for grape growers
Thinning and irrigation strategies play key role in offsetting effects of prolonged cool, wet weather.
By Gary Strachan I
don’t have to tell anyone who grows grapes in B.C. what kind of a season we had in 2011. It was a season like no other that I can remember.
We’ve had cold, wet springs before and cool summers before, but not quite like this year. I can’t speak for anyone else, but I encountered a few factors this year that I hadn’t thought of before . . . mostly because they had a greater impact on grape quality than they have in the past.
In the spring, it soon became obvious we were running late with bud break, then with bloom, and then with fruit set. Timing was mostly about two weeks late, but some locations were even later. On some sites this was complicated by damage to primary buds. If canes develop from secondary buds, that alone can delay the season by a couple of weeks, in addition to lowering the yield with smaller clusters and a lower number of clusters per shoot.
There have been lots of years when the influence of a cool spring was offset by a warm June, July and August. It didn’t happen this year. This was La Nina. We started late and stayed late. There seemed to be a ray of hope when we finally got warm weather this fall. It helped to bring the flavours and composition into balance but we never did catch up to the kind of maturation and pick dates that are characteristic of our regions.
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A head-pruned vine with canes of various lengths. The long canes were derived from primary buds that had not been damaged. The short canes were derived from secondary buds.
It was the kind of year in which the grower hopes for improvement in the weather but must prepare for the worst. What can be done about it? There are a few strategies that can assist the crop to mature earlier. The most obvious of these is to thin the crop as soon after fruit set as possible. The longer that thinning is delayed, the less it will affect the final composition and maturity date. The flip side is that we all hope for improved weather and don’t want to needlessly cut our yield. If we guess wrong and delay thinning in a cool summer, we could lose the whole crop because it may not mature before frost defoliates the vines. A conservative grower thins early. The gambler delays.
When thinning fruit, pay attention to the canes. If there has been bud injury, there will be an obvious difference in cane length between canes derived from primary and secondary buds. Remove the clusters from short canes first. The short canes are likely derived from secondary buds and those clusters will be smaller and slower to mature. If your canopy is too dense, remove the short canes first and then remove one leaf above the remaining clusters on normal canes. Avoid topping the canes unless absolutely necessary. Topping canes removes meristems, the source of auxin synthesis, which in turn diverts carbohydrate synthesis from the normal development of the vine until lateral canes are created to replace the
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British Columbia FRUIT GROWER • Winter 2011-12
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