Vintage 2019: Summer

The summer solstice, the longest day of the year was on June 21st and brought with it 3/4 inches of rain. At that time, we were still waiting for our grape vine flowers to bloom. It seems a bit late to me. Needless to say, at this time of the year, waiting for bloom, rain is not a welcomed event. On June 22nd, we notice that some of our Chardonnay were beginning to bloom. In our vineyard, Chardonnay seems to be the first to bloom. Then on June 25th we were hit with 2 inches of rain!
In 2017, we had rain during flowering and these photos tell the story of the damage that rain can do.

Understanding the parts of a grape flower is important in understanding what happens during flowering.

Vitis vinifera grape varieties have hermaphroditic (perfect) flowers, containing both male and female organs.
Why is rain during flower so detrimental?

• Rain can dilute the stigmatic fluid and interfere with germination of the pollen grains
• Cold temperatures, rainfall or high humidity are often associated with incomplete detachment of the calyptras leading to reduced fruitset
In addition:

• Temperature is an important factor in germination and growth of the pollen tube. Fruitset is greatly reduced when temperatures fall below 65^oF or exceed 100^oF

So far, we are not seeing the kind of rain damage that we saw in 2017, but we will have to wait and see what berry set brings.
References:
1. Nick K. Dokoozlian, Grape Berry Growth and Development.