Sex in the Vineyard - Weather, Vinifera, and Pollination - Madera, California (Early June 2010)
Wondering what this Spring has been like in our Orange Muscat Vineyard? It's been wet and cool so that's put a damper on the business of pollination. This means we've had scraggly clusters with fewer berries.
The grape growing areas of California are (normally) blessed with a “Mediterranean” climate (mild winters with a long, warm and dry growing season). It was in the Mediterranean region where Vitis Vinifera species which comprise essentially all the important wine varieties: Cabernet, Chardonnay, Riesling, Muscat, (including our Orange Muscat), evolved.
Our Orange Muscat crop will likely be smaller this year. Just look at these clusters! They are missing many small berries; the result of poor pollination resulting from the unusually cold and rainy spring.
Grapevines from the species Vitis Vinifera are self-pollinating. This may sound like it's easier than pollination that depends on bees, but several conditions must be right for self-pollination to occur. And we're not talking about mood music. Remember, these grapes love a Mediterranean climate.
For successful pollination a grain of pollen (the small male part, less than .001 inch in diameter) must fall from the anther and adhere to the stigma, a wet and sticky area of the pistil (the larger .1 inch diam. female part).
If temperature conditions are favorable, a tiny tube forms from the pollen grain, extending through the stigma and penetrating the ovule inside the pistil. There are two sperm nuclei inside each pollen grain. When the tube is complete, the sperm use it to join with (fertilize) two egg nuclei inside the ovule.
The resulting embryos each become half of a grape berry.
Hot or Not
Low temperatures and high humidity affect pollination. The anthers do not release pollen until the temperature is above 60 degrees F and the stress of dryness is necessary to pull open the outer part of the pollen sac. This year’s cool wet spring was unusual, especially in our part of the state. All those poor pollen sacs unable to share their goods.
We'd rather have had the moisture in the winter instead, but all things considered are grateful for the abundant snowpack in the Sierra Nevada which is our source of water, ending a period of drought.
We'll bring you an update later in the Summer when we have a better sense of what's happening with these grapes.