I write this on 12th September, right in the middle of the picking of the Sauvignon grapes and the beginning of the Semillon harvest. We still have about 10 days to go before starting on the Red Grapes with the Merlot. How is it shaping up??
The 2009-2010 winter was the 5th coldest during the last 20 years, being between 2-3° C colder than the long-term average. At the same time the winter rainfall was 30% deficit with regard to the long-term average over those winter months. Looking a little beyond the winter, the rainfall was deficient, from January to May, to a total of 115 mm- which is a lot. June had a mere 7 mm over the average, and July and August were VERY dry (see below).
We should bear in mind that the greatest Bordeaux vintages have been the driest ones rather than the hottest.
April was warm and dry and this is when the vine bud took place under excellent conditions and even a slight advance on 2009. May was a month of contrasts with local and violent storms accompanied by some heavy rains, in spite of the overall rainfall deficiency. The potential crop on the vine looked heavy. The vine slowed down in May, and conditions were uneven between the different parcels and even between vines. Pollen analyses, taken around 26th May, confirmed a relatively rapid beginning to the flowering, which reached mid-flowering from 4th-6th June, almost exactly the same time as in 2009.
This made it look as if the Merlot vintage would be around 23rd September. The setting started around 8th June and was general by 15th. Now the vine took on a delay due to some very cool and damp weather with some storms. Summer came in during the last 10 days of June (21st) and it was clear that we had coulure (shatter) and very uneven ripening on the bunches which closed from around 6th July on precocious vines.
July and August were above all very dry and, although we had some sizzling hot days when the temperature reached up to over 36°C, the overall temperatures were hot and fine without being extremely so. In July 54.5 mm of rain fell, which is only 28% of the long-term average here in Bordeaux. Temperatures were well above average. In August 59.5 mm of rain fell, which curiously is also exactly 28% of the long term average and temperatures were almost exactly those of the long term average. The vine liked all this and caught up all the delay that it had accumulated.
This catch-up meant that growers started their white wine vintage with the Sauvignon on 1st September, which is exactly the same as last year. By 10th one can say that 80% of it has been harvested and producers are delighted. To date this month we have only had 9.4mm of rain. The first 5 days were hot, reaching up to 32.1°C on 5th, the second 5 cooler but still in the mid-20s, and yesterday, 11th, it was up again to 28.5°C. Perfect picking weather and many growers say that the 2010 white wines will be finer than 2009 because of fresher and crisper acidity with perfect grapes.
The well-known vine grower and winemaker Denis Dubourdieu says the Merlot MUST be fine because of two factors that never lie. We have small grapes (due to the dryness) and a very low malic acid content in them. Picking of the Red Wine grapes is expected around 23rd September.