California calyptra.

It rained today; heavy at times, but mostly a miserable, stubborn drizzle that lasted all-the-grey-day-long.  And the temperature climbed to a whopping 65° F.   Hmmph!  Not exactly optimum conditions for bloom in the grapevines - which seems to be going quite slowly this year. Come back, California-sunshine.
The number of days that the grapevines are in bloom is dependent upon the weather.  When conditions are favourable bloom can take about 8-10 days, (but it can take as long as two weeks under cool conditions like the Napa Valley is experiencing now).  And, of course, the flower clusters on a grapevine will not all bloom at exactly the same time, so that spreads bloom out a bit.  Still, I think bloom is more protracted this year.  I have also noticed that there are more clusters per shoot and that the clusters seem to be a bit bigger than the past two years.
Do not be alarmed by this picture of detached grape flowers from one cluster of Cabernet Sauvignon at TWWIAGE (and hand-modeled by a coworker).  Although it looks like a lot of dead material; anthers, calyptra, stamens, etc., it is quite normal.  As few as 20 to 30 percent of the flowers on a cluster will develop into berries, most will fall from the cluster during the initial stages of berry growth.  Furthermore, a significant number of flowers will drop from the cluster about 8 to 12 days after full bloom: a stage commonly known as shatter.  Fruit set is not complete until after shatter.  Phew!  It's a jungle out there.  Fruit, set, now!

Bloomin' 'eck!

Yesterday, when I was working in the vineyard, stuffing shoots and suckering trunks, I noticed that bloom is rather advanced in the Cabernet Sauvignon vines.  How did that happen? There didn't seem to be much going just this time last week.  The weather was warm at the beginning of the week, but temps have cooled to the low 70s and it's been a bit windy. Whatever is going on the vines seem to like it.  Carry on buddies!

Bloom is bustin' out all over.

Everything is blooming in Vinoland, except for the Cabernet Sauvignon. But that is not surprising, as the Cabernet Sauvignon is always the last variety to go through bud break and bloom.
The wonderful weather we have been having in the Napa Valley of late is absolutely ideal for bloom. Vitis vinifera generally likes the temperature to be about 85°F during bloom and will quite happily bloom away in the heat - until temperatures reach above 95°F when, like me, the vines get a little toasty.  Temperatures above 95°F can result in bloom, and fruit set, being adversely affected.  The grapevines and I are so sensitive.

I doff my calyptra to you, Pinot grigio.

I noticed last week that the Pinot grigio vines were starting to bloom, just a little bit here and there.  A week later, I am estimating that they are probably about 60% through bloom, (or anthesis).  Just look at those calyptra coming off.
There is a lot going on out in the vineyard right now; flowering, shoot stuffing, suckering, sulphuring, weeding, mowing, etc.  Phew!  The vines are busy, so am I, but I am not too busy to pause and acknowledge that the vines are doing most of the work.  Go buddies!