Inside Knights Bridge

Canopy Pruning & Leaf Thinning

Canopy Pruning & Leaf Thinning

In our third and final posting on pruning, we discuss canopy pruning and leaf thinning.

Leaf Thinning in Estate Vineyard

Many of our loyal customers have asked us to keep them updated on our vineyard practice. Throughout February, we are posting a series of Journals describing our current project in the vineyards - pruning. In our third and final posting, we'll discuss canopy pruning and leaf thinning. Click here to read our first Journal on Spur and Cane Pruning or our second Journal on Removal of Previous Year's Growth.

Canopy pruning occurs after bud break, which usually happens in April and continues to harvest. A few elements of canopy management are tucking and thinning canes, removing suckers, and thinning leaves. The growing canes are tucked behind the upper wires to help them grow upright and to allow the new shoots and fruit to receive more sunlight. At this time shoots are thinned, which opens the canopy for more sunlight and air circulation, making it easier to manage the grapes and apply sprays when needed. Sucker, new plant material that sprouts on the trunk and cordons of a vine, removal keeps the vine from expending energy on extraneous growth and from interfering with operations in the vineyard.

Leaf thinning involves removal of leaves from vines again opening the plants and fruit up to more sun exposure and air flow. This happens throughout the growing cycle until just before harvest. Leaf thinning just prior to harvest helps to ensure leaves are not in the harvested fruit. During the growth stage the vines produce canopy and clusters, which mature through the stages of flowering, berry set, and verasion (the start of fruit ripening). The amount of air flow during the time of flowering is critical because too much wind can damage the flowering clusters, leading to poor fruit set and a decreased crop yield. Too little air flow through the rest of grape maturation can foster mold and bacteria damage of the fruit. Leaf thinning also regulates the sun exposure of the clusters. After verasion this is monitored closely because crops can easily be damaged by overexposure and the value of the fruit can be harmed. When clusters are overexposed there is a higher risk of sunburn, which damages the grape skins leaving them vulnerable to fungal infections, hinders the sugar accumulation of the berries stopping them from reaching full ripeness, and destroys the pigment in the berries causing less color extraction in the fermenting juice. At the same time too little sunlight can cause vegetal off flavors called pyrazines, to develop in the berries which will affect the aromas and flavors of the finished wine.

Fruit thinning often occurs before the grapes go through full verasion, and it removes the less ripe clusters. Although there is no conclusive evidence that this practice must be done, many believe that it allows the vines to concentrate all their energy on fully ripening the remaining clusters and helps to develop the complex flavors that characterize a finished wine. Regulating the overall yield of the vineyard prevents over-cropping of the vines over time, which causes a significant decrease in the quality of the grapes and shortens the life of the vines.

This journal highlights many of the pruning practices of Knights Bridge Vineyards. Most vineyard managers, including our own, use these general practices changing things slightly depending on the vineyard site. Information for this journal came primarily from an interview with Josh Clark Vineyard Manager at Clark Vineyard Management and from information gathered at UC Davis workshops.

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Canopy Pruning & Leaf Thinning