There are few experiences greater than being in the Napa Valley in Autumn. Driving around at night when the air becomes colder and heavy, you can smell deep, profound aromas emanating from the pressed skins (called pomace) in the vineyards which literally perfume the air.
……….And the colors!! Vibrant colors bounce off a mantle of green grass brought about by fall rains. Did you ever wonder why certain vineyards become yellow and others red or both? Probably not. Well, without becoming too technical here is what you don’t see.
The petiole (leaf stem) swells with the onset of colder and longer nights which does two things. It causes the Palisade layers in the leaf to collapse and chlorophyll production ceases turning the leaf yellow instead of green.
Secondly, at this time of year, all of the vine’s energy is now headed for the roots where it will be stored for bud break and initial shoot development next spring. Some vines and vineyards have contracted virus infections carried by mealy bugs or nematodes. This interferes with the movement of fluids in the vine and some of the anthocyanins (the stuff that makes tannin in wine) are trapped in the leaves turning them completely red or a mottled red. Some examples are Red Leaf Roll and Red Leaf Mosaic which effects the leaves more than the vines. The vines will wake up around mid March, as they do every year, and they will be just fine.
You probably will not be able to look at a vineyard the same way again. In any event, when you are about to enjoy a glass of V. Sattui wine, just give our vineyards a little mental toast for all of the hard work they do.