(Fruitionsciences) - This discussion is a follow up with our last blog on the 2017 maturation

What is the situation end of september?

A general disorder in sugar accumulation is observed in northern California. The trend is widespread and shows sluggish sugar accumulation rate across many different vineyards. The extend of the phenomenon indicates that slow fruit ripening profile is a seasonal tendency of 2017. This observation has been echoed by many winemakers, perplexed not only by the sluggish sugar accumulation rate but also by the slow evolution of other fruit  compounds  such as aromas and tannins.

In our last blog (here) we shared a general observation of low berry volume by the last week of August 2017. We formulated 2 hypothesis: either berry volume was lower than usual, possibly because of a reduction in seed number per berry or berry volume was lower than usual because of a delay in berry mass accumulation.  4 weeks later, the slowly moving amount of sugar per berry observed across many contrasted locations in Napa, Sonoma, Livermore and beyond confirms that a significant delay in sugar loading is observed and this trait can be considered a specific trait characterizing the 2017  vintage  in Northern California. Of course sugar concentration may increase rapidly, but it is mainly due to berry losing water, not because berry is loading sugar.

Nitrogen or Water can not be culprits 

To accumulate sugar plant photosynthesis activity and sap flow rates must be sufficient to convert CO2 in sucrose and transport sucrose from the leaves to the fruit. Can any of those 2 processes explain why we observe such a generalized slow ripening in 2017?