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Canopy Management for Pacific Northwest Vineyards

Canopy Management for Pacific Northwest Vineyards

EB2018E
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Mercy Olmstead , Kathleen Williams, Markus Keller
Growing grapes in variable climates is discussed, as well as basics such as canopy components, goals, light and temperature effects, assessment methods, and techniques for canopy manipulation.
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Growing grapes in the Pacific Northwest (PNW) can be challenging and rewarding due to highly variable vegetative growth within the region. For example, growers with vineyards located in maritime climates (e.g., Puget Sound American Viticultural Appellation [AVA]) are largely  concerned with controlling vegetative growth and increasing fruit exposure to sunlight, while those in the inland PNW (e.g., Yakima or Columbia Valleys) often need to adjust their vegetative management to protect their canopy and fruit from sun exposure. Growers need to carefully assess their vineyard site, including soil characteristics, annual precipitation, and precipitation timing, to determine the best fit with specific grape varieties in terms of potential vine vigor, productivity, and fruit quality. Proper canopy management can lead to good profits for the grower and high quality fruit for the winemaker.

Throughout the world, management of grapevine canopies has changed over the years. Many European countries now use a tightly spaced, minimal height vineyard with no trellis support, while some New World countries opt for a wider spacing and trellis system. Benefits can be realized for both types of systems and those in between, depending upon grape variety characteristics and climate.

Definitions of Canopy and Canopy Components

Canopy, as defined in this publication, includes all vegetative and reproductive plant parts that are above-ground: the trunk, cordons, canes, spurs, shoots, fruit, and leaves (Figs. 1 and 2). The management of canopies involves manipulating these components in order to achieve a balance between vegetative and reproductive growth for optimum fruit yield and quality.

Shoots are comprised of vegetative and reproductive growth in the form of leaves, tendrils, and fruit from the basal end to the growing tip, produced in the current growing season. The rachis is the main structure of the cluster on which berries develop (Fig. 2). The growing tip is where leaves emerge; monitoring shoot tip growth can distinguish between optimum growing conditions and vine stress. Shoots originate from buds that occur on canes, spurs, cordons, the trunk, and even from below ground level (when they emerge as suckers).

Canes are mature, lignified wood from the current or previous season’s growth. Canes and shoots are comprised of nodes, with spaces between nodes defined as internodes (Fig. 3). At each node is a composite bud containing three sets of buds (primary, secondary, and tertiary). The primary bud is the most fruitful, while the tertiary bud is the least fruitful. Buds can be

Figure 1. A typical cordon-trained grapevine and its associated components before spur pruning.
Figure 2. Grapevine shoot components.
dissected before pruning to aid in determining the potential crop load (Morrison, 1991) and help with decisions about pruning severity (Fig. 4).

Pruning weight is determined by the amount of wood that is pruned off one vine in a single season. This can be used in formulas to determine how many buds should be removed and/ or left on the vine as part of balanced pruning techniques (Reynolds, 1988). The amount of pruning wood is determined by how the canopy is managed throughout the previous season. Thus, if a vineyard is on a particularly vigorous site, a large amount of pruning wood can be accumulated. However, on a low vigor site the canopy may be fairly small, leading to shorter and thinner canes and lower pruning weight.

Crop load is used to describe the ratio of yield to the pruning weight or leaf area. Vine capacity defines the maximum amount of shoots that the vine can support and fruit that will

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