The most important decision

When to pick your grapes was always an important decision. In times past one picked when the grapes had sugar levels sufficient to allow the winemaker to make a wine with the desired amount of alcohol, even allowing for some extra sugar to come from chaptalisation.  Historically, when it was often quite hard to get grapes to be fully ripe, achieving this level of sugar ripeness was the primary goal.  If the highest level of ripeness you were likely to get in the grapes perhaps was only potentially 12 degrees of alcohol, you did not have to worry about whether the acidity would be adequate.  And not much was known in the early days about phenolic ripeness. So sugar ripeness alone determined the picking date, making the decision when to pick relatively straightforward.

But today this decision is more challenging because of two factors  -

1. Risk of “overripe” grapes is greater because of the warmer climate

In today’s warmer climate grapes can ripen easily and can quickly become overripe with a commensurate undesirable reduction in acidity. Grape varieties vary in the relationship between the rise in sugar levels and the reduction in acid. Some grape varieties lose acidity more quickly than others as sugars rise. But all grape types have an easier time today getting fully ripe - and some grape types can become too ripe in a matter of days. 

Also, as the climate has warmed, if picking dates have as a result moved to late August or early September when previously they were towards the end of September or early October, the reality is that each day the grape remains on the vine starts to matter more. This is simply  because each day in late August is a warmer day than each day in late September. Harvesting grapes in October is more forgiving than if you have to harvest in late August. A day or two either side may not matter. But the picking “window” is shorter if you must harvest in August. Managing picking teams is more difficult if the window is smaller. Picking schedules can become very tight. The days of leisurely picking in October on your own schedule are apparently over.

2. The need for phenolic ripeness 

Today we better understand and acknowledge the importance of a second type of ripeness - the ripeness of the skins and the seeds - which is quite different from sugar ripeness. This Is called phenolic ripeness, which is needed to produce optimal ‘flavor” and structural ripeness in the wine. The path to phenolic ripeness does not necessarily run coincidentally with the arrival in the grapes of ideal sugar ripeness.  Typically - and this is a generalization in the old world  - phenolic ripeness comes later than sugar ripeness. So one may have grapes on the vine with the perfect sugar/acid balance but that have not yet reached full phenolic ripeness.   Without adequate phenolic ripeness a wine will have some green flavor notes and underripe tannins.  Within certain boundaries, it seems phenolic ripeness has more to do with luminance ( ie light) than heat, whereas sugar ripeness is more determined by levels of warmth.  So they may not arrive at the same time. Whether they do depends on the particular climate of the year. If they do not arrive more or less at the same time, a winemaker will have to choose which type of ripeness to prioritize. Waiting too long for phenolic ripeness may result in grapes with high potential alcohol and low acid, giving flabby wines. Picking too soon may result in perfect balance between fruit and acid but suboptimal flavor elements and unripe tannins because phenolic ripeness was not yet achieved. In extreme seasons the choices can be quite stark. In Barolo’s 2017 vintage, for example, the unusually long period of dryness shut down the grapes’ vegetative cycle. The result was that the picking date was largely determined by the desire not to lose too much acid, thereby having to accept that the skins and pips would not be fully ripe.

So there are at least three three dimensions that factor into choosing a picking date - sugar ripeness and the commensurate related acid level, and phenolic ripeness.  Most growers making a red wine prioritize phenolic ripeness over sugar ripeness - not least because they have some ability to control delaying sugar ripeness. There are many vineyard techniques to try and slow down the rise in sugar in the grapes - managing the leaf canopy for example to slow photosynthethis or allowing yields to increase a little by not green harvesting. Slow down the sugar ripening process and you better align the optimal sugar ripeness with phenolic ripeness.

There is a point of view that, in a year of extreme imbalance between sugar and phenolic ripeness - beyond what can be compensated for by the techniques used to slow down sugar ripening - if you pick early and so risk some less than optimal phenolic ripeness, the resulting wine may over time in bottle recover somewhat from that. Time has the effect of moderating the imperfections in the tannins. Whereas if your preference in such a case is to pick late to ensure full phenolic ripeness, the resulting high level of sugar ripeness and reduced acid will always mark the wine. Time has no ameliorating impact on a wine that starts out “flabby”.

Greater awareness of these interlocking variables make the choice of picking date today even more challenging than previously.  There is more understanding about the likely consequences of choosing a particular day over the next. More informed decisions of course give the winemaker more control. But the decision is still a stressful call - an irreversible decision which puts in play the work of a whole year in the vineyard. If you ask a vigneron what “mistakes” he has made or what he would have done differently in relation to a particular vintage where he feels the wine might have been better, the most common answer you hear is that he picked too early or too late. 

If you have any doubt about the importance of picking date, try a few 2006 red burgundies.