Fall vineyard colors. Something about them makes you want to grab a bottle of red, put another log on the fire, grab a blanket and someone to get under it with…. No? Maybe just us.

Yellows, oranges and browns are the tell-tale signal of fall. Each year, the bright, green reminiscent of spring and summer in leaves fades away, giving way to the cozy fall colors that make you want to break out the scarves and gives you a sudden urge for pumpkin spiced lattes in the red Starbucks Christmas cups. Or, if you’re in Berkeley like me, at your favorite local coffee shop, serving quite possibly the strongest cup of Joe I’ve ever had, which is great for my words per minute and blog productivity! Wheeeee! Shout out to Local 123

Sonoma, CA

Let’s get back on track, shall we? Pretty fall colors. People travel all over the world to witness the beautiful color change. Tourism often escalates during that time, especially in areas back east in New York or Connecticut and out west in wine country. Anyone ever wonder why the leaves change? For grapevines, it’s a very important phase in the life cycle of the vine.

Color change is dictated by many environmental factors including temperature, but more importantly, the length of the day and night. Chlorophyll is the pigment for the leaves’ green color. When the days start to get longer, the leaves develop and the acquired energy from the sun produces carbohydrates to store for next year. Grapevines are very sensitive to the amount of sunlight and darkness in a day. When sunlight is available for a long part of the day, the pigment Chlorophyll is constantly being produced by the energy from the plant but also fades from light exposure at the same time. The main job of Chlorophyll is to catch the light energy for photosynthesis to turn it into carbohydrates. At the same time, the light also fades the pigment, under which are yellow and orange pigments.

When the days become shorter, all of a sudden the cells that normally divide and expand no longer expand and just divide, forming a blockade on the road that is used to transport carbohydrates from the leaf to the vine, and vice versa, nutrition is blocked coming from the soil and rootstock to the leaf. When temperatures are cooler, this process is expedited. Since that vital communication between the leaf and vine is cutoff, production of chlorophyll eventually stops, exposing the yellow and orange colors, called xanthophylls and carotenoids. These pigments also assist chlorophyll during the growing season. The carbohydrates left in the leaves contribute to the red and purple pigments in leaves called anthocyanins.

*If ‘anthocyanins’ rings a bell, it may be because it is also what the pigments in red berry skins are also called anthocyanins. The juice that is inside is clear until maceration takes place, extracting these pigments. But this is for another day…

This process can be said to most deciduous trees and plants, but let’s get to what’s different about winegrape bearing vines and how it impacts viticulture. The carbohydrates and sugars created from photosynthesis will primarily go to ripening the fruit. The vine must distribute the carbohydrates, especially late in the ripening season, to finish the ripening of the offspring, which is most important, and then secondly stones the carbohydrates within itself, until the quantity is sufficient to last the vine until the days become longer again, and when there is enough sunlight to begin the production of chlorophyll for the new season.

When frost occurs in the fall, during or after harvest, the leaves will become brittle and eventually fall. If a frost does come before harvest finishes, the leaves cannot collect any more chlorophyll and therefore cannot produce sugars. The fruit will be as ripe as it can be. Sometimes, this is why, especially in cool continental climates, the sugars, and therefore alcohol, can vary from year to year and often have lower alcohol contents than wines from a warmer, or more consistent climate.

Until next time, we hope you enjoy the fruits of last years harvest, staying warm, and all that is fall and perhaps a little more the fleeting fall colors!