Efflorescence, or simply flowering, of the vines is one of the most sensitive and crucial periods in the life of a vine.

If you remember in my last post I talked about crucial times in the life of a vine. At that time it was all about bud break when the dormant bud on the canes breaks forth with leaves and flower buds.

The initial inflorescence (the flower bud) contains hundreds of flowers but not all flowers will turn into berries. Depending on weather conditions a large number of flowers simply fail to get pollinated. As a general rule one flower equals one berry. Now and for the next couple of weeks the flowers will start emerging.

Before each flower opens up there is a little cap on top of each flower that in some cases one can see still stuck on the end of the grape berry. The cap falls off and a single flower emerges.

The actual flower consists of a central ovary that is destined to become the grape berry and usually 5-6 anthers that look like petals to the unaccustomed eye. Anthers produce the pollen that falls onto and fertilizes the ovary to create the grape berry.

Pollination of the Vines

One of the very interesting facts about the European grapes we choose to grow (vitis vinifera) is that the vines are hermaphroditic. This means that the flowers have both male and female components and most importantly are able to self-pollinate. Other species of vines, for example North American (vitis labrusca and vitis aestivalis) vines, are either male or female and pollination requires the intervention of a third party, most typically a bee or some form of insect.

Although vinifera vines do not need insects to pollinate them, there are good studies to show in organic and biodynamic vineyards that pollination and fruit set markedly increases in the presence of a healthy insect population. It appears on the face of it that it should be a pretty straightforward process, but as with everything Mother Nature does when it comes to sexual reproduction – it’s not that simple.

You see it all depends!

In order for that simple process to occur vines need two things at the time of flowering, warmth and sunlight. Here, just like with bud break, timing is everything. If it is cold and wet during this time, pollination will fail to occur and berries fail to form.

Flowering to Fruit Set

The industry calls this period of time “fruit set”. The weather conditions during fruit set determine not only the amount of the crop but also the quality of the crop. If the weather is sunny and dry many more flowers get pollinated and more berries form. When there is cloud cover, wind, and rain the flowers can fail to pollinate that winegrowers refer to as “shatter.” The French have their own term, “coulure” that describes a flow of flowers from the stem that failed to pollinate.