What effect can the rain can have on grapes?

What effect can the rain can have on grapes?

by Beth Heiserman


This past weekend, I was watching a movie about a couple falling in love at a vineyard. It was driving me crazy watching it because it had so many false facts about vineyard care. While I was watching this love story, I remembered that this was a sequel to another one that I remembered that had so many wrong facts that I looked up on their Facebook page and saw already thousands of people, commented what I was thinking. They said that if there’s a frost that it would kill the entire crop which can be incorrect. It depends upon what stage the vines and grapes are in. Right now, our vines, just like the movie, the vines are in dormancy.

As, I was sharing my experience about watching this movie to a friend, someone else texted me to ask me about the weather and how it effects the vines.  I looked up the rainfall, Santa Clarita has received this year. In January 2019, 4.47 inches and February, so far, is 4.05 inches. Last year January received 2.03 inches and February for the whole month was .21inches. What a big difference. Plus, last July through September, we had a heatwave that lasted longer than it should have. With little rain and a lot of heat, didn’t give us a big quantity of grapes that we harvested this past year.

When you have too much rain it means that you’re going to have a lot of grapes but sometimes depending upon when the rain occurs, it can affect the flavor of the grapes also. So, when it rains when the grapes are growing sometimes, it’s too much water that will cause the grapes to be a little bit waterier or a lighter flavor compared to less rain then the grapes are more concentrated and thicker skins.  Think about this, when you buy grapes at the market that you eat, that sometimes there’s no flavor because they over-water them. Too much water, will decrease the sugar levels. People that grow grapes to eat, grow for the quantity not necessarily the quality.

When it rains during the growing season, we have to prune off a lot more excess foliage. There is concern for diseases and mildew. Plus, it creates destruction and/or compaction of the soil which creates issues when you drive the tractor in the vineyard.

Fourth, the excess rain can cause grapes to have more water at harvest and decreases the sugar levels. The grapes have gone through veraison and are gaining sugar now, so we hope to see less rain. Finally, really wet soil over a long period of time could drown your vines if they are not on well-drained soil.

Currently right now there is not too much rain because the grapes have not started the next years cycle to damage anything. We are still in dormancy, so as much colder rain as it gets it doesn’t hurt it. You do need a certain amount of cold for good harvest the following year which we are getting the right amount of cold to make sure that.  It would be different if we were not in dormancy. You need approximately 45 days of 54° weather, and we have that.  Single digit temperatures can damage or kill the vines. Fortunately, here in Santa Clarita, it generally is never that cold. Yes, its been very cold and we have seen a few snow flurries, but it hasn’t reached temperatures to be concerned.