Light Needs of Grape Vines

Site Selection

• Grapevines need at least six to eight hours of sunlight each day. When choosing a site to plant young vines, analyze which areas receive the most sunlight and which areas remain in the shade. Look for wide open areas that are free from light obstructing structures like buildings and trees. When shaded areas are unavoidable, opt for areas that receive morning and early afternoon sunlight and late afternoon shade. Early day sunlight is always preferable to the harsher late afternoon sun, especially in climates with harsh summers.

Trellising and Canopy Management

• Grapevines are supported by weak stems, which require them to need some type of additional support. Use trellising methods that allow sunlight to infiltrate the canopy so that all parts of the plant receive sufficient sunlight. Ample sunlight is especially important during the last cycle of the fruiting process. Arrange the grapevines on the trellis so that all the leaves receive sunlight and the shoots are spaced out enough to promote good air circulation.

Pruning

• Superfluous shoots like the suckers growing from the base of the grapevine, and thin weak shoots, are pruned off to allow the fruit-bearing shoots to receive the necessary sunlight. Only 1-year-old canes produce fruit-bearing shoots, so canes older than one year also need pruning off. Pruning is best done during the vine's dormancy, which is during the cool season after it's leaves have fallen off. However, prune fastidiously because over-pruning leads to excessive and vigorous growth.

Symptoms of Insufficient Light

• Judge whether grapevines are receiving enough light by examining the plant for certain symptoms. Poor fruiting or no fruiting is indication that the grapevines are not receiving enough light. Shoots that are thin and spindly are also a sign that the vines are planted in poor lighting. Grapevines that lack sunlight become weak, which makes them more susceptible to disease and pest problems as well.