After harvest ended in Bordeaux for whites and reds, comments and articles about the 2015 vintage were all over the web : it seemed like another great vintage. At first, during the summer, 2015 was expected to mimic 2003 due to the extreme heat and drought in July. Now that harvest is over, it appears that the whole 2015 season ressembles more 2005… which was noted as a great, or even an amazing vintage. Indeed, the thermal time curve of 2005 (sum in degree days) is very close to 2015’s, confirming the promising potential of this vintage. Let’s look back at this past season weather conditions to understand what makes a great vintage.
Winter precipitations were moderate and sufficient to maintain a non-limiting water supply early in the season. Due to a cool spring, bud break was observed late, around the beginning of April for Merlot. The months of April and May were warm and watered moderately. These conditions favored soil active mineralization and good nutrient availability which positively impacted vine growth and functions. Thanks to recent research results, we know that high growth rates before veraison are synonymous with higher yield for the current year, as long as nouaison is satisfactory.
Finally, thanks to an abundance of sunshine combined with the lack of rain, flowering started relatively early in the Bordeaux region, around May 20 for Merlots and completed over less than a week. Indeed, early June, flowering was also complete for Cabernets. Except for blocks affected by mildew and Black Rot, the summer started with inflorescences without shatter which confirmed a good yield potential for harvest, the first hallmark in a great vintage.
On June 13, we entered a period without rain along with high daytime temperatures and high nighttime temperatures (ie. above 20 ° C). Water deficit pre-veraison was gradually observed across many Bordeaux vineyards from early July on. The severity of water deficit was more or less pronounced depending on grape variety and area. Merlot on highly drained soils experienced the most severe water deficits while Sauvignon Blanc experienced a more moderate water deficit during this period without rain. The lack of water resulted in a decreased rate of berry cell proliferation, reducing berry size and increasing the skin / pulp ratio, second hallmark of a great vintage. Late July, veraison started slowly and heterogeneously. Fortunately, the long awaited rains came on time to unlock active sugar loading in berries, allowing a quick start of the fruit ripening process, third hallmark of a great vintage.
August was particularly rainy, up to 120 mm in some places, which kept water deficit low. This maintained berry turgidity and avoided yield losses. Relatively high temperatures allowed a smooth completion of sugar load in most vineyards. Thus, technological maturity was reached very quickly and as early as end of August for the first Merlots, promising a good alcohol content. Phenolic maturity started early, giving it every chance to unfold properly and reach ripe tannins, fourth hallmark of a great vintage. However, the summer heat and water deficit in July resulted in lower total acidity, in part due to accelerated consumption of malic acid.
Temperatures at the beginning of September contrasted drastically with those of July and August. Indeed, it was particularly cold in the Bordeaux region (-1.7 ° C compared to monthly averages) with very few days above 25 °C. These conditions resulted in a slowing down of phenolic maturation process while preserving the anthocyanins. Cabernets, which are more dependent on late season heat to complete maturation, were more sensitive to this temperature drop. Merlots, which were already very advanced, could be harvested at their peak quality potential. In some areas, botrytis outbreaks were detected following abundant rainfall in September (80 mm in the Médoc) which in turn induced harvesting Cabernets that were not quite ripe.
In conclusion, the 2015 vintage is very good, even excellent for Merlot, rejoicing the right bank. There are more heterogeneity among Cabernets explained by heavy rainfall in the Médoc and cool temperatures in September and October. However, for those who were able to wait and delay the date of harvest, the quality is there. The year will be marked by a proper alcohol content, low acidity and “silky” tannins. The 2015 Bordeaux will be a wine that can be drunk young, but we will have to be patient to see his full aging potential!