Now is the time to monitor and control canopy growth in vineyards, particularly with red varieties. Canopy growth can occur via careful management of irrigation and nutrition, and may be shaped by careful trimming. A moderate approach to irrigation can reduce berry size, which has positive quality outcomes; and it can also reduce or stop shoot growth. There is little point in “forcing” a vine canopy with a heavy nutrient and water regime if that growth only ends up being trimmed onto the vineyard floor. This is wasteful in terms of creating more work but also leads to a heavily “thatched” canopy as a result of forcing lateral growth after vigorous shoots are repeatedly trimmed. This leads to excessive shading, and also makes spray penetration difficult. Few growers now practice the heavy ‘RDI’ stress that was in vogue years ago, and instead opt for mild deficit over a longer period, typically from fruit set to veraison. This is a critical process, and should be handled with care and diligence. It is best performed using soil moisture monitoring equipment, and requires daily observation. Often slight stress can be achieved by irrigating to partially fill the soil profile, rather than full replenish it. When extremely hot days are predicted, it will be necessary to fill the soil prior to the heat of the day to avoid damage and loss.
There are some signs that the vines are responding to mild stress, including the loss of tendrils, (or they are easily knocked off), shoot growth slows or stops, leaves feel warm to touch during the day, and fruit starts to ripen earlier. Growers will need to plan their irrigation regime with consideration of their soil and irrigation system. If the canopy is well controlled with this method then often only light trimming is required, or even no trimming at all.