Fruit thinning, green harvest, restricted yield, whichever name it may go by there are few canards as distinctly pervasive as yield restriction. Across Europe, the belief that yield restriction is directly correlated with amplified wine ‘quality’ is so widely held that one can almost predict the nature of questioning at any tasting, visit or seminar. Let’s stop for a second; just how accurate is this belief? Is yield restriction really a fundamental requirement of high-quality wine production or is this hypothesis flawed?
In this series of posts I will attempt to tackle a range of questions from the recently released 2019 stage 1 MW exam. I will tackle these questions in a somewhat relaxed manner, a manner in which I hope I will not only be able to develop my own understanding but also add value to the journey of my readers. Let it be said, I’m no Master of Wine. As such please do not expect a ‘winning answer’ Instead I will try my best to dissect each topic with rational and reason, providing both an answer and a learning resource.
In tackling this question there are three underlying assumptions which one should attempt to validate in order to achieve a binary answer. The first is to acknowledge that if the answer to this question were to be yes, it would suggest by default, that yield restriction is a one size fits all solution to improving quality, regardless of region or variety etc. The second would be that were the answer to be yes, no wine produced without intentional yield restriction could be of ‘high quality’ The third, and final, conundrum, is the challenge of defining exactly what it means to be a ‘high-quality wine’
The most common technique associated with the range of viticulture practises centred around restricting yield is green harvest (although yield restriction is not its primary purpose) An additional method utilised to some extent in restricting yield is vine training; however, when discussing viticultural yield restriction it tends to be green harvest which is the most common method employed.
Having emerged roughly in the last 30 years, green harvesting as a quality-centric viticulture technique is a relatively recent practise, but remains one which has grown exponentially in popularity. The practise emerged out of little more than anecdotal postulation, with the science remaining unclear at best. It is important at this point to differentiate between fruit thinning as a means of vine health management and as a method of purposefully restricting yield with the aim of improving quality. Fundamentally the assumption is that as a result of increased leaf to fruit ratio (principally the leaf provides sugar to the vine through photosynthesis) when one restricts yield (by reducing the number of bunches on the vine) the rate of sugar accumulation is increased in the fruit that remains.
There are a number of stylistic qualities commonly associated with wines which have undergone a programme of yield restriction in the vineyard. These are higher alcohol levels, darker colour, riper fruit character, less greenness, less acid, altered tannic structure and more concentration. However; is this always the goal and are these qualities defining variables of ‘high quality’ across all varieties and styles?
If we consider fruity, high acid wines, like rosés or of varieties such as Sauvignon Blanc, Chardonnay (in this respect as a component of sparkling wines in particular) Riesling or Grüner Veltliner etc. are we particularly looking for less acid? darker colours? higher alcohol and increased phenolic development? White grapes are fundamentally very different to red grapes, in their case a larger yield has the ability to slow ripening, thus allowing more time for green characters to dissipate and for ripe characters to develop. Additionally, in the case of warm regions positioned at the extremities of wine production, it is important that the vine has a large enough crop to sufficiently distribute the inherently larger accumulation of sugar.
In addition to the above, vine age is a further variable which one would need to consider when determining whether or not to restrict yield. A young, vigorous vine which is not yet well established to its terroir may require yield restriction whereas a 20 year old vine, already well-adapted and self-regulating may not, assuming the answer to this question were yes we would restrict both yields, potentially unnecessarily as one may achieve balance naturally whilst one might not. Considering the question within this context it seems more suitable to suggest that opposed to being presented as a universal determinant of producing ‘high-quality wine’ yield restriction be seen as a tool which can be employed dependant upon the variety, age and desired stylistic charecteristic of the wine.
The second point of contention; can a wine be considered ‘high quality’ if it has not undergone yield restriction? Having previously noted that the use of green harvest (with the intention of restricting yield) is a fairly recent phenomenon, it defies logic to suggest that wines which have not undergone this process can not be considered high quality, especially considering the esteem in which many wines predating the popularity of the process are held. Taking in to account specific producers there is a wealth of evidence available to suggest that high-quality wines are indeed produced without yield restriction. By any metric, Nyetimber is one of Englands best sparkling wine producers. Brad Greatrix, winemaker at Nyetimber, states that it is his personal experience that the quality of their wines actually increases proportionally to yield, and as a result green harvest is not typical at Nyetimber.
Finally, semantically defining high quality is of particular difficulty. If high quality is to be defined as the financial value achieved for sold wine then W. Blake Grey has shown through statistical analysis that with a range of high-end Napa Valley wines there is a positive relationship (R = 0.22) between yield and secondary market prices meaning that wines from higher yield years are actually likely to cost more. A perhaps more appropriate measure of high quality is structural balance and critical acclaim, metrics which are measured and attributed somewhat simultaneously through critic scoring and awards. Making further reference to Nyetimber, it is evident that where green harvest is not typical, a wine remains able to achieve both balance and critical acclaim.
To summarise, based on the aforementioned I do not believe it to be true that yield restrictions are necessary in order to produce high-quality wine. Not only does it appear evident that the result of direct yield restriction is more closely related to desired style opposed to quality, it appears more appropriate that it be viewed as a tool, a tool which is employed dependant on a range of variables such as region, variety, vintage yield variation, vine age, desired style, climate, terroir and clonal vigour variation. Furthermore, it seems to me somewhat one-dimensional and ill-fitting with the diversity of varying wine style to suggest that a single, relatively new, practise should be a universal defining factor in producing high-quality wine.