Leaf Canopy Management in Viticulture: Timing of the First Hedge Trimming

Delaying the timing of the first hedge trimming is of limited technical value in vineyard canopy management. Its impact on lateral shoot growth and must composition is minimal.

There are several different methods available to train grapevines. Of these, trellising techniques such as Guyot or Cordon de Royat facilitate vineyard operations and mechanised work. Once attached to the trellising, vine shoots require trimming (tip pruning) to facilitate access between rows and phytosanitary treatments. However, the first trimming inhibits further longitudinal growth of the shoots and instead stimulates the growth of lateral shoots from secondary buds at the base of the leaves. The management of this secondary growth is a tedious task that can influence the health, yield and composition of grapes at harvest. One potential solution is to simply carry out the first trimming later in the season to delay lateral shoot growth as much as possible.

A study conducted by Agroscope in the vineyard of La Côte in Switzerland from 2003 to 2006 compared a normal trimming with a late trimming. Two trimming variants were applied, each with two repetitions: 1) first trimming corresponding to the ‘end of flowering’ stage of development (BBCH 67-69, late June), and 2) delayed first trimming at the ‘start of veraison’ stage (BBCH 81, late July). The timing of the first trimming was the only difference between the two treatments.

Delayed trimming has little impact

The results showed that climate conditions in the respective year had the greatest impact. The delayed trimming reduced lateral shoot growth in certain years (Figure 1A) and slightly reduced levels of phosphorus (−0.03% DM) and magnesium (−0.03% DM) in the leaves. It had no significant impact on either yield or grey mould (Figure 1B). It reduced total acidity (–0.4 g/l eq. tartaric, Figure 2) and increased pH (+0.02) in the must, without influencing the accumulation of soluble sugars. Delaying hedging can be beneficial in certain years to limit lateral shoot growth and reduce foliage overcrowding in extremely vigorous vines. However, the physiological and economic value of delayed hedge trimming remains marginal and its impact on must composition is limited.