Vine Growth

It's getting close to wake up time for grapevines, time for them to come out of winter dormancy. Due to the warm weather that we are experiencing in the Northeast, we are already hearing that the sap is flowing in the vineyard. This is definitely a prelude to budswell and budbreak, and it is only mid-March!
My husband and I were having a "discussion" about vine growth and quality fruit so I whipped out the following diagram from van Zyl:

The above diagram can be found in many locations, including the third edition of Ronald Jackson's Wine Science.² The diagram charts the growth of various parts of the vine as it comes out of dormancy.

• Shoots: Shoots and leaves grow rapidly after budbreak and then declines to near zero as veraison is approached. By the time the vine is flowering, it has achieved about half of it's growth.
• Berry growth has three stages:
  
  • Stage I is an initial rapid growth rate shortly after flowering.
  • Stage II is a period of very slow growth rate.
  • Stage III is a second period of rapid growth as veraison is approached.
• Roots: Roots are actively growing during flowering and again post harvest.³

Knowing the growth rate of the various parts of the grapevine is key to understanding vine balance. The leaves provide the surface area of photosynthesis and the creation of carbohydrates which then goes into berry growth and ripening. During the growing season, the most efficient sink of the carbohydrates produced in the leaves are the berries. That makes sense because the plant is in the business of reproducing itself and ripening it's fruit to make it attractive to various creatures who will feed on it and in the process aid in the dispersal of seeds.
1. van Zyl, J. L., 1984, "Response of Colombar grapevines to irrigation as regards quality aspects and growth", S. Afr. J. Enol. Vitic., 5, 19-28.
2. Jackson, Ronald S., Wine Science: Principles and Applications, Third Edition, Elsevier, Academic Press, 2008, pg. 109.
3. Vine Water Deficits Caused by Reduced Soil Water Availability