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How to know when to harvest?

Harvest season has begun in the Cape Winelands and knowing when to harvest is a fine art. Choosing the perfect moment is a mix of style, balance and wisdom, let’s take a closer look at what makes grapes ready to harvest.

It is useful to know a bit about how a grape grows and develops. First, the vine comes out of winter dormancy and will start to bud in spring, around September. This is followed by flowering around November, where the flowers hope to be fertilised and be set to become a grape, known as fruit set. After this, the berries start growing in size and after 40 – 50 days will start a phase of ripening called veraison.

Ripening happens because of grape bunches exposure to sunlight and the ambient temperature of the vineyard. This is why it is important to carefully consider how to manage the leaves of vines during veraison, balancing the need for sun and the natural functions of the vine made possible by the leaves.

Veraison is where the unripe berries start to convert their high levels of acidity into sugars over a period of 30 – 70 days, depending on the cultivar, climate, and the style of wine they are destined to become. As the berries ripen the level of acids falls and the levels of sugars and pH rise. This is where the balancing game starts since some wines need higher acidity, such as sparkling wines like Sparklehorse, compared to dry table wines. On the other extreme are grapes that are harvested very late in the season to make dessert wines, such as T Noble Late Harvest. These berries have been left on the vine and picked up Botrytis (Noble Rot), which allows the berries to gently dehydrate and concentrate the sugars while still retaining a backbone of acidity. These berries are harvested as late as May.

Knowledge and wisdom are essential in this test of patience, the winemaker and viticulturists will keep a close watch on how balance is changing with increasing frequency while factoring in how the climate of the growing season has progressed and weather forecasts. There is always a chance of an unseasonal rainy period that would force the berries to take on too much water, disturbing the balance and even burst their skins.

In recent years there have been significant advancements in measuring the physiological ripeness of berries with the two main focuses on the ripeness of tannins and phenolic compounds. Tannins are compounds mostly found in the pips, stalks and skins, and when unripe, have a harsh “green” flavour. Phenolic compounds contribute to the colour, flavour and aroma of the wine. In this broad category of factors, there is much evolution in technology on how to measure development and ripeness. Since this introduction into the equation of knowing when to harvest, the quality and consistency have grown exponentially around the world.

At Ken Forrester, all the berries are harvested by hand, and this careful and wise consideration of ripeness allows efficient use of time and effort to ensure the berries are picked at their prime which sets the ultimate quality of the end wine. During this exciting time, come visit the farm to feel the vibe and experience the quality ranges of wines created by Ken Forrester, such as the Reserve, Icon and Cellar exclusives.