Flowering on Fast Forward

It takes two seasons to make a bunch of grapes. This is because bud initiation in grapevines starts the year before the bud bursts (Y1) This is when the fruitfulness of the buds for the following year is determined and heat, sunlight and the nutritional status of the vine in the early summer in Y1 are important for fruitful buds the following season. In Y2 those buds will break and shoots will grow with or without inflorescences (flower clusters) which after flowering will be our grape bunches. If the weather in Y1 was sunny and warm, there is the potential for up to 3 clusters per shoot. If the weather in Y1 was cold, wet with low light levels, the number of clusters/inflorescences will be lower, if any at all. This means that our 2025 potential yield has already been set to some extent by the conditions of 2024. The weather and conditions  in 2025 can help or hinder us achieving that potential yield at critical times such as flowering which we have just gone through at record pace this year. 

Flowering is essential for the vines to produce any fruit and ideal conditions are warm and sunny weather which we have had in abundance so far this summer. The heatwave in June  has meant flowering was on fast forward and finished before Wimbledon had seen a ball in action. Historically, flowering of vines in the UK has coincided with the Wimbledon fortnight but this is the earliest start and finish to flowering that I can remember in our vineyards. With a decent fruit set we are now at pea sized berry stage in most varieties.  A very different story to 2024. 

Last year, flowering started later and due to the cold and wet weather at the end of June and throughout July, it was a long and extended flowering period over 4-5 weeks. Pollination was not as effective as we would have liked resulting in an uneven fruit set, bunches ripening at different times and a very low yield. Wimbledon was over before flowering had finished.

To what extent will the 2024 weather have impacted our 2025 yield potential? At the all important time of bud initiation last years weather was cold, wet with low light levels. It is still too early to tell the full impact on this year’s buds,  but whilst flowering and fruit set have seen almost perfect conditions,  most varieties are carrying no more than two bunches per shoot (three is not unusual in high yielding years) and bunch sizes in some varieties are moderate. Yield estimates will start towards the end of the month when bunch numbers and estimated bunch weights will give us a fuller picture of the harvest potential. 

However this lovely hot and sunny weather should be giving next year’s buds a great start.