Managing your vineyard canopy in summer (i.e. fruit thinning) is crucial for achieving the best yield and fruit quality. This practice adjusts the vine balance, crucial in the UK’s cool climate where growing degree days (GDD) are limited and ripening fruit in autumn is challenging.
Timing
Effective canopy management involves timely interventions throughout the vine’s phenological stages, ensuring uniform crop load and ripeness. Early fruit thinning, done shortly after fruit set, has the most significant impact as the vine’s resources are directed to the remaining fruit for longer. This task is easier to do after the first leaf stripping pass. Late thinning, at veraison or shortly after, has minimal impact due to the shorter period for resource allocation. However, it’s easier as the fruit is visible, changing colour and identifying underdeveloped bunches is simpler.
Bud Rubbing and Shoot Selection
New growth requires removing unwanted shoots from the trunk. Bud rubbing by hand ensures thoroughness. Shoot selection around the crown or head of the vine to thin and spread shoots more evenly, allows each grape bunch space to grow. Positioning is more important than the individual shoot’s strength as a strong shoot does not necessarily give you a strong bunch of grapes. Thinning promotes aeration, reducing humidity and disease.
Tucking In and Wire Lifting
Tucking in involves moving shoots between foliage wires to form a hedge shape, with fruit growing around the 4th and 5th buds. Raise the first wire above the fruiting zone, tucking in and lifting as necessary throughout the season.
Trimming
Once growth is beyond the top of the trellis structure it can be detrimental to air flow and shading. This job is best done by machine and typically requires 2-3 passes per season. Ensuring each vine has at least 10 mature leaves to ripen whilst avoiding overshadowing from neighbouring rows is preferred.
Leaf Stripping
Removing older, redundant leaves from in and around the fruit zone enhances aeration and sun exposure, aiding ripening and spray penetration. Start by stripping the east side to allow morning sun to dry the canopy followed by a strip on the west side at a later date and before harvest to make fruit visible to pickers. Experienced workers are preferable to machines for selective, careful leaf stripping.
Predicting Yield
Accurate yield prediction is crucial before fruit thinning. Early season counts of inflorescences (flowers) are essential. Count large enough samples, including vines with no fruit, for an accurate estimated average number of bunches.
Estimate bunch weight using previous years’ data or industry standards. Multiply average bunch weight by the number of bunches and vines to calculate predicted yield. Adjustments depend on the growing season, variety, rootstock, vine vigour, target parameters, and contract constraints.
Chris Buckley is the Business Director at VineWorks.
Vineyard images © VineWorks, 2020
