Harvest has begun all over Europe in one of the strangest growing seasons ever experienced. While it’s never too early for commentators to pronounce on the likely quality of the wine, in Bordeaux the Institute of Oenology sets five conditions by which the success of a wine vintage can be judged. These can be found in the extract below.
At this point of the vintage cycle, three of the five conditions can be assessed, with the last two not really possible until after the final grapes are picked.
The first two conditions are fulfilled: there was regular flowering and good, even fruit set in spring; there will have been enough water stress before veraison for the third condition. There have been sporadic rains over past few weeks after the driest summer since 1959 – July was exceptionally hot and sunny.
Overall, 2020 is an extremely early season, around two weeks ahead of average. According to the latest “maturity report” from the research laboratory Oenocentres in Pauillac, this year is characterised by small berries, high alcohol potential, and the lowest acidity since 2003. Colour and aromatic compounds are still relatively low at this point, so ripening for the reds will be some weeks yet; the white harvest begun across Bordeaux.
So 2020, so far, has been a good, if extreme, growing season for Bordeaux, although with some risk of excess ripeness and alcohol in certain soils. It remains to be seen how the next few weeks of harvest will measure up against the Institute’s criteria.
Five conditions for success: a checklist
(From Inside Bordeaux: The Châteaux, the Wines and their Terroir by Jane Anson)
One of the key takeaways of this book, I hope, is that you can find good wines in every year if you know where to look – and that you don’t always need the reassurance of a high price tag if you know a few shortcuts. This starts with knowing how vintage quality is assessed, and therefore what you should be looking for and where.
In Bordeaux, the success of a wine vintage is subject to five conditions, as set by the Institute of Oenology. Think of this as a checklist that individual vintages either meet or do not:
- Swift, early flowering
- Fruit set
- Hydric stress at the right time
- Drought and moderate heat
- Dry and sunny weather during harvest
1) Swift, early flowering and (2) fruit set, both of which encourage consistency later in the season for the colour-change (veraison) and grape ripening. This is equally true for red, white and sweet wines. It should be noted that temperature is the most important thing during fruit set rather than a lack of rain – obviously rain is not ideal, but if temperatures don’t drop too low, the process can continue fairly smoothly. If not, the issues are coulure (flowers that don’t set into fruit) and millerandage – uneven bunch development with hard green berries that never ripen and sit next to normal grapes, complicating viticulture right through to harvest and sorting the grapes in the winery.
3) Hydric stress at the right time, which means sufficiently in advance of veraison so the green parts of the vine (shoots, leaves and so on) stop growing and concentrate their energy instead on giving sugar to the berries. If rain continues for too long, berry size will be too big for truly concentrated wines. White wines are a little less affected by this than red, and this is when soil-type really kicks in, but as a blanket rule green growth should stop three to four weeks in advance of veraison for red grapes, and one to two weeks for white grapes. Essentially this means a dry July is best, particularly the second half of the month.
4) Drought and moderate heat during the ripening period after veraison, with a sufficient but not excessive hydric stress, to encourage the production of sugar and other phenolic and aromatics compounds, and to thicken skins. This is the point at which the isobutyl-methoxypyrazine compound (also known as pyrazine, or IMBP) responsible for green pepper flavours in Cabernet Sauvignon can be reduced to below perceptible levels. Overly dry or hot conditions mean ripening can block, which again is where terroir is key. This is again a stage where red grapes take the heat better than white, as aromatics and fresh acidities are so vital to white wine quality.
5) Dry and sunny weather during harvest, with enough light rainfall that growers can wait for ripeness in different plots and grape varieties. A little rain is essential at this point for Sauternes estates that need the process of noble rot to start. Too much rain can cause not only rot but dilution and loss of fruity aromas across all colours.
As this makes clear, it matters what happens when, so 200mm of rain during flowering or in September is not the same thing as 200mm falling cumulatively over the entire season. It is important to track what happens in different parts of the region – if, for example, St-Estèphe and Margaux have very different weather patterns in the same year, and why Left Bank gravels might do far better than Right Bank clays in certain years.
Recent red wine vintages: how they have fared
2005 All five
2006 First three conditions
2007 Only the final condition, number 5
2008 First three, plus 5, but not 4
2009 All five on some terroirs; with 3 arriving a little late in less well-draining soils and some blockages of ripening on particularly dry soils during 4
2010 Four of the five, with just 1 difficult because of cool weather during flowering, particularly affecting Merlot
2011 1 and 2 perfectly; 3 yes, but with extreme drought causing blockages on sandy and pure gravel soils; 4 and 5 only partly
2012 No to 1 and 2; 3 almost entirely; 4 yes; and only partly 5
2013 None of the five. Some châteaux released no wine at all
2014 Only partially met 1 and 2; did not meet 3; partially met 4 and completely met 5
2015 All five, although 4 more complicated in northern Médoc with rains in August
2016 All five conditions, but 3 a little later than ideal
2017 Yes 1 and 2 for those vines not affected by frosts in April; 3 was not met except on extremely well-drained soils; 4 and 5 only partially met for Merlot, more fully for Cabernet Sauvignon
2018 Yes to 1, but followed quickly by mildew which affected 2; yes to 3, especially on well-drained soils; yes to 4 and 5