The Role of Flowering in the Life Cycle of the Vine
In the Northern Hemisphere, this is usually sometime in May or early June. The temperature must be at least 60 degrees Fahrenheit for flowering to occur. Reaching this threshold is rarely an issue in California, though it can be in some cooler parts of Europe.
Flowering in the vineyard occurs over about a week and a half. During this time, the embryonic grape clusters are fertilized and pollinated. The vines are very susceptible to weather swings when this is happening. Various methods are used to prohibit frost damage including wind creation using fans, furnaces and sprinklers.
Grape flowers are usually about one-eighth of an inch in diameter. Most vines will begin flowering in their second or third year but will not produce grapes until their seventh year.
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