Spring at Unionville

May 13, 2016

Our unpredictable winter was followed by a spring of the same. All the great warm spring days we had just a month ago allowed the vines to wake up from their winter slumber and start to bud. Unfortunately, we just had a few serious cold snaps that can kill those delicate buds. According to our vineyard manager, Roni, we made it through the winter virtually unscathed.
Buds are actually formed on last year’s crop. They are tiny shoots that are dormant over winter on the vines’ canes. Roni and his crew cut back the excess cane earlier in the year. Now that the temperatures in the vineyard are starting to get above 50 degrees, these tiny shoots or buds emerge from nodes in the vines’ remaining canes. This is known as bud break. This is the most critical time of the year in the vineyard, a late frost now can reduce, if not ruin, our crop for the year.

When I was in class in Washington last month, one of our assignments was to examine frost damaged buds. Not easy. We had to use razor blades and carefully slice half of the tiny bud off. The remaining half was placed under a microscope. If the primary bud (the bud has actually three parts - primary, secondary and tertiary) is still green, we’re looking good. If the primary bud is brown, then the crops for that year are in danger. The secondary and tertiary buds can be a slight insurance for the crop, but harvest and grape quality are greatly diminished. A few years ago when I was living in Texas, a few portions of the High Plains area had three consecutive late frosts. Strike one, two and three. No crop for that year.

Luckily, we were spared that plight, and now in the vineyard we are starting to see the emergence of little leaves. Until this point the buds are pulling up carbohydrates from the plant for energy. With the development of leaves, photosynthesis can begin. The plant can start taking energy directly from the sun and accelerate the pace of additional growth. In my viticulture class this is discussed as Sources and Sinks. Until the leaves appear and start bringing in energy from the photosynthesis, the buds are all sinks, as they withdraw energy from the plant. When the photosynthesis occurs, this reverses the process and are now called Sources. Kind of like when your kids get out of college and start paying off their student loans.

We’re still not out of the woods yet. Actually, not until the grapes are harvested, are we actually out of the woods, but more on that later. For now, we can breathe a little easier that we’ve made it through the late frosts and onto the next challenge. I’ll discuss more in the next blog.




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