As we head into summer, the countdown to harvest has officially begun – but while our focus is often on the beautifully ripened, ready-for-picking grapes, the earlier stages of grapevine development are all crucial to producing the perfect bunch of grapes.
The annual growth cycle of the grapevine consists of several stages: budburst (or bud break), flower cluster initiation, flowering, fruit set, berry development, harvest and dormancy. Bud break means the previously dormant buds begin to grow shoots. This is also the time of year where suckering (the removal of non-bearing shoots) happens. This is an important viticultural practice, to ensure the correct number of shoots on your vine, as well as ideal spacing. This forms an important part of canopy management, and greatly influences both yield and quality.
After suckering is complete, the flowering stage follows – and yes, grapevines do have flowers, though grapevines do not need insects like bees to pollinate them – they are self-pollinating. During this time, no interventions are made in the vineyards. Flowering is a sensitive stage in the development of the grape bunches. Sudden changes in temperature, rain and heavy winds can all have a negative impact flowering – which in turn affects the yield. Flowering is also the only other time of the year (other than directly after the grapes have been harvested) that we irrigate our vineyards.
Once flowering is complete, the vine moves into berry set – this is where the fruit starts forming. During this time, important vineyard interventions include opening up the canopy (through leaf removal, side-shoot removal and lifting the wires). This is important to get sun onto the bunches as early as possible, to ensure the berries do not suffer sunburn later in their development. Opening up the canopy creates both light and air movement – this also lowers the humidity and decreases the risk of diseases like Botrytis cinerea.
Berry set leads into berry development, which continues throughout the summer. Veraison is a key moment in the berry development: it is the onset of ripening. Both white and red grapes undergo veraison, but it is visually more noticeable in red grapes, as this is the point where the grapes start turning red. If you look closely, you can also spot veraison in white grapes – the berry begins to soften and the skin turns from a very opaque green colour to a more yellow-green shade, and it loses some of the opacity.
Once veraison starts, the final countdown to harvest has begun, and winemakers begin to monitor the grapes for all the indicators of ripeness, until it is time to pick.