Vineyard Management
Where did the warm summers go?
JUDIE STEEVES
Coping with cooler weathermeans paying close attention to the fine balance between vegetative growth and cropping level.
By Gary Strachan F
or grape growers, the last two years have been hard to accept. We’ve seen published reports that
the earth’s oceans are warming, and that average summer temperatures have increased. But not in my vineyard. Is this the way climate change will affect us? Wild swings between too hot and too cold? Great! It’s an old problem. Everyone complains about the weather but no one does anything about it. Perhaps it’s time to examine strategies that can lessen the impact of less than optimal weather in order to achieve more consistent grape quality. The grape vine has an annual development cycle, referred to by horticulturalists as the phenological cycle. In an average year, stages such as budburst, bloom, fruit set, and veraison have a date which is specific to each grape variety and each growing location. Unless you have a much better memory than mine, it’s a good idea to keep note of when some of these events occur. Comparison of the current year with the dates when things went well (or not so well) is the first step in good management that will enable you to adjust your vineyard management to get the best possible yield and composition. A widely-held assumption in vineyard management is that yield is inversely related to quality. In some
30 COURTESY OF DR. PAT BOWEN, PACIFIC AGRI-FOOD RESEARCH CENTRE
circumstances this is true, but the more fundamental truth is that quality is related to a fine balance between vegetative growth and cropping level. Changes in weather can affect that balance by accelerating or delaying vine and berry development. Good management must always work toward restoring that balance. In a cooler than normal spring, followed by a cool summer, it is not unusual to have the various events such as bud break and fruit set delayed by a week or two behind the normal. Strategies to accelerate development could include both fruit thinning and
shoot thinning. Fruit development can also benefit from fruit exposure as early in the season as possible. Be cautious to not over- expose fruit on the south or west side of the vine, especially if leaf removal was delayed for (say) a month or more after fruit set. In many cases, a
cool spring that delays fruit set may
have little impact if the summer has normal temperatures. Vineyard growth may develop rapidly enough during the summer to produce a normal veraison and harvest date. Hot summers can be as much of a problem as a cool summer. Grape varieties seem to differ in their ability to tolerate high temperatures. In warm years this can cause some varieties to mature later than expected. In general, the Bordeaux varieties seem to be less sensitive to high temperatures in the 40-degree range than Burgundian or Germanic varieties. I suspect there is no clear cutoff
= P. 905-984-4324 • F. 905-984-4324 • E.
sales@vinetech.ca •
www.vinetech.ca British Columbia FRUIT GROWER • Spring 2012
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