Flowering has begun

Flower clusters on Rondo vines

Well, May was a strange month. Much cooler than normal. Only 11.7°C degrees mean air temperature compared with the three prior years being about 13°C. And whereas it started out dryer, it ended wetter at 112.5 mm compared with 60-70 mm in the last three years. These values are reported for Newport, only 7 miles away and on the water much like we are.  

The grape starts its annual growth cycle with bud break around March when daily temperatures begin to rise above 10°C (50°F), and ours were right on schedule. The start of this cycle is signalled by a "bleeding" of the vines that were pruned during winter. I did not notice bleeding, but I did notice bud break which I documented in April.

About a month or more after bud break, the process of flowering begins with small clusters resembling buttons appearing on the tips of young shoots. Flowering occurs when average daily temperatures stay between 15–20°C (59–68°F) which is generally in June around here, but not this year. Today it will only reach 10°C.

After the initial clusters appear, the flowers start to grow in size with individual flowers becoming observable within a couple of weeks. During this stage of flowering, the pollination and fertilization of the grapevine take place producing grape berries containing 1-4 seeds in clusters. Most cultivated Vitis vinifera vines are hermaphroditic, with both male stamens and female ovaries, while many wild grapes are either male or female. Hermaphroditic vines are more likely to self-pollinate and produce fruit and are not dependent on pollinator insects. Cross-fertilization can occur between different varietals. 

Despite the cool temperatures, the grapevines look healthy and have started to flower. So we are again encouraged. We've probably left more shoots than we should have on the first vines this year, but it's really encouraging to see those little clusters forming.