Thanks for your thoughts, Wes. I have given serious thought to your proposed possibilities.
I have read a few things that lead me to believe that the same vineyards in the same area in Oakley and Antioch consistently produce the “small berried” Mourvedre, not resulting from vintage variation alone. Some area vineyards do not yield these coveted grapes, so I cannot say that all CoCo old vineyards that include Mourvedre exhibit this trait. I am leaning towards a genetic link, whether it be a favorable mutation that has occurred in California or prior to importation.
I have been skimming research articles to try and get a better grasp of what I am looking for:
“Berry size variability in Vitis vinifera L.”
L. FERNANDEZ, M. PRADAL, G. LOPEZ, F. BERUD, C. ROMIEU and L. TORREGROSA
UMR BEPC Campus Agro-M/INRA, Montpellier, France
“Ecophysiological, Genetic, and Molecular Causes of Variation in Grape Berry Weight and Composition: A Review”
Zhan Wu Dai,1 Nathalie Ollat,1* Eric Gomès,1 Stéphane Decroocq,1
Jean-Pascal Tandonnet,1 Louis Bordenave,1 Philippe Pieri,1 Ghislaine Hilbert,1
Christian Kappel,1 Cornelius van Leeuwen,1 Philippe Vivin,1 and Serge Delrot1
Am. J. Enol. Vitic. 62:4 (2011)
I have been told more than once that the pre-Prohibition Mourvedre vineyards that are still in use in the areas mentioned in my inquiry fall into two categories: smaller and larger berried. Of the two, some very positive statements were made about the small berries; conversely, the larger berry grapes are best tucked away in Field Blends.
One thing that has struck me is that I have not seen mention of the older Sonoma vineyards where Mourvedre is found. One guess is that, as a respondent commented, the CoCo and San Benito vineyards might have been planted to Spanish cultivars, while other old California vineyards have French derivation. I don’t know.
I have read a few articles on Spanish Monastrell that mention small berries, a detail that is not as common (but by no means absent) in evaluations of French Mourvedre vines.
Yes, good grapevines can be poorly farmed. Yes, bad winemaking can ruin good juice. No single element defines the final product.
My current topic of nerdy wine learning is not a jibe at any other producer, area, variety, clone, or grape characteristics. I just am chasing a very specific topic down the rabbit hole.