Grapevine Flowering Video: How Spring Weather Influences Bloom and Fruit Set in Vineyards

Wet, warm spring weather throughout April and May delayed flowering, or bloom, in our vineyards by two weeks. (While rainfall during spring was unseasonably high, overall rainfall levels for the year were ample and welcomed after several drought years.) When the warm weather finally arrived in early June, both Chardonnay and Cabernet Sauvignon clusters bloomed at the same time (see video), which is a rare occurrence because Russian River Valley—home to our Chardonnay grapes—is about 15 degrees cooler than our Bordeaux variety vineyards in Alexander Valley.

Good weather is critical for a quality, and mostly importantly, even fruit set. Once the warm temperatures arrived, fruit set happened quickly this year, and that excelerated pace contributed to the most desirable situation in certain areas: a homogenous, uniform crop. (Grape berries consistent within the cluster make much better wine.) The warm weather also ensured very little shatter occurred in our estate vineyards. Minimal shatter of the grape clusters also means uniform berries within the cluster and ultimately consistent flavor of grapes within a cluster.

We did have some gusty winds early June, which did affect bloom. Strong winds cause a higher instance of shoot loss. We thin the grapevines of their shoots, but we prefer to decide which shoots we’d like to remove.

All of these factors—the uniform clusters we desire coupled with the rainy spring and windy conditions during bloom—will certainly make 2010 a unique, yet challenging growing season that has the potential of being a great vintage with the right vineyard management practices (and ideal weather during harvest).

Next we’ll begin shoot positioning of the vines in preparation for veraison.

Curious about this critical part of the growing season where berries begin to form and grow? Watch the above video and send us your questions.