To understand what is meant by Cool Climate wines it is important to understand how the vine functions and how this affects the quality of the grapes (and therefore, the subsequent wines).
At the end of autumn the vines send their sugar reserves back down to the rootstock for the subsequent season. In the process, the leaves change colour, a cork like substance is formed in the stem of the leaf, which subsequently drops off. As this process happens, there is a build-up of a hormone called abscisic acid, which sends the vine into dormancy for the winter period.
In order for the vine to wake-up properly in the spring, this hormone needs to be degraded by cold units (below -2*C for at least 4 days). In the event of a lack of cold temperatures this hormone remains present in the vine and can lead to a number of problems. The most important of which is uneven bud-break. If your vines don’t bud evenly it can lead to a number of problems; uneven growth along the canes, uneven flowering and berry set, to name but a few. This ultimately will result in uneven bunch sizes and varying ripeness (which is a nightmare for picking dates and the subsequent components within the grape – high sugars in some and a lack of phenolic ripeness in the skins resulting in green tannins, high acidity and a lack of colour or flavour).
A further problem is also that if cold temperatures are not obtained and warm day-time temperatures persist, one may witness premature budding, making the vine more susceptible to incremental spring weather resulting in higher fungal pressure (more chemical intervention) and / or damage to the vulnerable new shoots from wind, hail, rain etc. I often compare this phenomenon to a lack of sleep in humans, as one is often less performant after a poor night’s sleep. Long-term, this may also contribute to a shortened life-span of the vine itself (which is why “old vines” are often a rarity in South Africa when compared with the European continent). Premature pruning will trigger the vine into budding early, bringing with it all the problems previously alluded to. The later one prunes, the longer the vine can “sleep” and the better it will perform, with less need for chemical intervention and with a better natural immunity against drought, excessive heat, fungal pressure or infestation from predator insects.
To conclude, colder temperatures allow for better bud-break and late pruning allows the vine to recuperate from its efforts of the previous season. Pinot Noir and Chardonnay are particularly susceptible to warm weather and a lack of dormancy. This is why these two varietals perform best in the cooler winter climates of Champagne and Burgundy as opposed to the warmer South of France. Therefore, planting these two varieties tends to work better in regions such as the Overberg, Hemel en Aarde Valley, Elgin and the Cederberg as opposed to Paarl, Wellington and the Swartland.
Since joining Seven Springs I have made a few minor changes to our viticultural cycle to allow for better dormancy (by pruning as late as possible in August, thus allowing for a longer window of opportunity for “cold-units). As you drive by the vineyards in many parts of South Africa, you will notice numerous farms start pruning as early as June, which is poor practice (but convenient for the scheduled holidays of farmers). One has to intervene when the vine requires, as opposed to when it suits us human beings. Mother nature will always win this particular arm-wrestle and to work against her will only bite you in the ass later on in the season
Cool Climate regions refers more to areas with colder winters as opposed to cooler summer temperatures (which also has on stress levels of vines in season), but winter is the key that unlocks true potential.
As the old saying goes, “you can make a bad wine from good grapes but you cannot make a good wine from bad grapes”.
Augustus (Gus) Dale, Vigneron at Seven Springs