After a seemingly interminable spring rainy season, a bit of warmer and sunnier weather in the later part of June and the beginning of July finally coaxed the grape plants in the North Willamette Valley into action. By the 4th of July, many vineyards reported the beginning of the second stage of grape development, i.e. “bloom”. This is the flowering of the grape plant that can occur anywhere between 6 and 13 weeks after bud break. With bud break this year not happening until the middle to end of April, bloom was most welcome when it came and signaled that the plants have caught up a little in their annual life cycle, having started 5-6 weeks later than normal. With bloom in early July, most vineyards seem to be only 3-4 weeks behind now.

Bloom is an extremely important time in the vineyard because if all goes well it raises optimism for a productive year. On the hand, if rainy, cold or windy weather interrupt the self-pollination of the grape flowers, it could make for a poor set, meaning smaller clusters or smaller berries or both and thus less production.

The pollination process in grape plants occurs when the individual grape flowers open by shedding their cap, called the calyptra. As the cap falls away, sometimes called shatter, the stamens are exposed and pollen is released. A grape plant is hermaphroditic and so the pollen usually falls on the plants own pistils, the female part of the plant, and germinates by penetrating the style and ovary of the pistil. If it is rainy or windy, the pollen may be blown or washed away before it completes its job. Cold weather is also problematic because the ovaries literally close up, making germination more difficult.

Although the green flowers of the grape are not very noteworthy as flowers go, the plant does release a pungent odor from the base of the pistil during bloom which is supposed to be an aphrodisiac. And although it may not rival the sweetness of Shakespeare’s rose, to a winegrower that aroma of fruit flowering is pretty exciting.

This entry was posted on Wednesday, November 9th, 2011 at 9:10 am and is filed under Vineyard Updates. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.