Vineyard: Flowering & Fruit Set

We finally experienced flowering and fruit set in the vineyard! It was a little slow this year as the temperatures have been up and down in Paso Robles, CA. We’ve been surprisingly cool, but this week is picking up to the 100 degree days. (not sure if I’m ready for the hot, hot heat yet!)
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Now that we’ve had the flowering and fruit set occur, what does that mean? It means a lot as this is the development of the fruit for the year! It’s a crucial time that occurs, after the leaf canopy’s growth begins and the calyptras appear. The calyptras (caps for short) look like itty-bitty green grapes, but actually they are just spheres holding the pollination parts and pollen. Many plants require pollination from bees, but vines are wondrous self-pollinators. The flowers have their own male and female parts.
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Once ready, the calyptra opens to show a pistil and stamens holding pollen. The pollen is softly transferred to the pistil slowly fertilizing it (it’s a slow dance, let’s say), which eventually produces seeds. These blossoms are not protected, which leaves them susceptible to weather elements such as gusty winds, hail, and extreme temperatures. It is a nail biter as these elements can “shatter” the outcome of the harvest in the fall. As mentioned in another blog, vines like consistent and slow developing temperatures, not extremes. This year (2018) has shown to be not perfect, but positive:
“Shatter happens when it gets too hot. Shatter also happens when temps get below 70 degrees and over 90 degrees. When the temps are below 70 and above 90 and it is too windy then pollination doesn’t occur very well. This photo shows that our crop is good, nice weight, and nice loose clusters. All in all, we have had only moderate shatter and a good fruit set so far.” – David Parrish
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So, now you’re probably wondering what shatter is. Shatter is when the clusters fail to develop to full maturity. Flowers can remain closed and therefore, unable to pollinate…meaning no berries. The vine is trying to preserve it’s carbohydrates because it becomes focused on staying alive against the elements. What this means is that there will be less clusters at harvest, which equals less production for the winery.
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Once flowering and pollination takes place, fruit set occurs.  This is when the fertilized eggs form seeds and pericarp tissues form a berry, kind of like an envelope around the seeds.  The berry’s size will be impacted by the number of seeds. A berry with no seeds is smaller and a berry with up to 4 seeds will be larger. The reason berry size makes a difference is if you have a cluster with various berry sizes, it is difficult on the ratio of skin to pulp for the winemaker.
A fully grown berry is 75% pulp, 20% skin, and 5% seeds. Pulp is essential for flavor and aroma in the wine. The main component is water and the second being sugar, which is vital for yeasts to eat during fermentation (creates alcohol). Skin is important for color, flavor, and aroma as well as the tannins, which will impact a wine’s texture and structure. The seeds also contain tannins. As you can see if you have a higher ratio of skin to pulp, this will mean a more tannic wine and that the winemaker may have issues with the fermentation process, which is important for alcohol to develop. On the flip side, if there is too much pulp (happens from too much water in the berry), this may impact color and flavor.
To avoid issues during fruit set, viticulturists begin thinking after the year’s harvest about the vine dormancy, root moisture, and soil health as these will impact the fruit for the next season. Pruning is also important for the new growth. Ultimately though, it does depend on the weather each year, but growers will do all they can outside of that factor.
As you can see, there is a lot that goes into just the grape itself and it begins prior to even bud break. It is just a reminder that it takes a lot of work to get to the glass of wine.
Next up, the berries will begin to grow in size:
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Stay tuned for berry growth and soon, veraison, which is when the grapes turn color…my favorite time in the vineyard as I find it fascinating…well, I like it all, but veraison is really cool to see.
Cheers!
Cecily