It's wintertime in Wine Country and our vines at Collier Falls are in a state of dormancy. As the temperature drops and the days get shorter, a physiological change occurs within grapevines that allows them to survive the cold winter months.
First, the vine sheds its leaves, slows down its metabolic processes and stops producing energy through photosynthesis. At this stage the plant relies on the stored energy it has accumulated through the growing season in the roots, trunk and cordons. This energy will be essential to kick-start the transition out of dormancy in a few months when the spring arrives.
Vines can survive the cold winter temperatures in Dry Creek Valley because of chemical changes that help protect their living cells inside. Water inside a plants’ cells can freeze during the winter, which can cause permanent damage if the cells were to rupture. During dormancy, grapevines have an amazing natural defense to this threat. Vines shut down the absorption of water from the root system so the vine does not take on any additional moisture, and it moves water out of the cells and into the inter-cellular area where it can safely freeze without causing damage.
What we don’t want is a heat spell in late winter. That's because it can trigger a premature awakening of the vines from their dormant state, and leave them susceptible to damage if the cold weather returns. Cover crops offer some protection against this issue, because the vegetation traps the colder temperatures near the soil, and helps to ensure the vines stay dormant until spring. In the meantime, we’ll put another log on the fire and open a bottle of Zinfandel to stay warm