Grape berry development

I’m going to give you a brief update on berry development to date here in Oregon.

Currently the North Willamette is coming toward the end of  phase 1 in berry development: flowering to lag phase. In the first stage of berry development (phase 1) the berries are growing from cell division. Canopy size, water and nutrient availability influence the amount of carbohydrates available for cell division. Vines with big canopies, lots of water and nutrients will produce large berries with high cell numbers. conversely small canopies and stressed vines will produce small berries with low cell numbers. Equally influential on berry size is seed number.  Seeds make auxin and gibberellins (plant hormones) making the berry a stronger sink for assimilates. Lower seed numbers per berry result in less cell division. High numbers of seeds produce greater amounts of hormones stimulating cell division. The final size of the berry is limited by the number of cells in the berry and the extent of expansion and or the degree of shrinkage (from dehydration) in phase 3.

At lag phase, phase 2 of berry development, the size of the cluster is said to be half that at harvest. Growers use this metric to estimate the potential yield of their vineyards and how they are going to crop thin. The problem with this metric is that its very hard to determine exactly when lag phase is without continually measuring berry volume and waiting for it to plateau.  Some models suggest lag phase is 55 days after first bloom, other models say its at 1200 GDD (this is measurement of heat units for a growing season) and finally some people go by seed hardening. What am i going to do this year? Seeing that we’ve had seed hardening for over a week and we’re only 45 days post bloom im going to wait until next Monday. Currently we’re at 1140 GDD for the North Willamette and i think we should be right on 1200GDD when i start sampling.

http://www.winebusiness.com/weather/index.cfm?weatherLocationId=22

Now the Rouge Valley is ahead of the North Willamette by 2-3 weeks and some of the vineyards are starting to go through veraison (phase 3).  Veraison is when the grapes change from being hard, green and acidic to soft, getting color and accumulating sugar.

For more on berry development.
http://www.extension.org/pages/31096/stages-of-grape-berry-development