Vine Balance and Yield

There is a commonly held notion in the wine business that yield and quality are inversely related. This simple maxim hides a physiological fact that exists for every grapevine. In reality, proper vine balance is responsible for optimizing both yield and quality.

Dr. Stan Howell of Penn State University explains grapevine balance as “the point where reproductive and vegetative growth are maximized in a sustainable way.” Reproductive growth is defined as fruit production while vegetative growth is expressed as shoot, leaf and root growth as well as thickening of the vine’s perennial structures. No cultural practice has greater impact on wine quality than does balanced crop production said Howell.

In his research, N. Partridge of Michigan noted that both under-cropping and over-cropping yielded fruit of lesser quality. He concluded that vines are properly balanced when they produce the greatest amount of ripe fruit with no reduction in vegetative growth.

To help balance vines at Cinnabar, Vineyard and Estate Manager Ron Mosley employs the three golden rules of winegrape growing:

• First, prune vines to 15 shoots per meter of cordon length. Allowing more shoots than this produces excessive shading. (See drawing.)
• Second, trim shoots to 36 inches in length with a maximum of 15 to 18 leaves. This is the ideal range for ripening two clusters per shoot.
• Third, the crop to pruning weight ratio should be seven to one. In other words, the crop should weigh seven times more than the canes (hardened shoots) that are removed the following winter.

Source: The Grapevine Newsletter, Penn State University

~ if you liked this post, please share it