I've had a few questions lately about frost protection so I wanted to talk about how we've reduced or chances of late spring frost and early fall frost and raised the ovall temperature of our vineyard.
So the area we cleared orginally for the test vineyard was right beside the road. We chose this area for a few reasons being that it was easily accessable and it was already nearly cleared of trees. What we didn't know at that time was that with mountain areas the wind moves up valley during the day as it heats up and cold air moves down walley in the evening as it cools down. The road beside the clearing runs the lenght of the valley so it is a perfect conduit to bring warm air up the road during the day and cold air back down at night. Another thing we did not know of was that this spot beside the raod was in a low spot relative to the area around it. For the location of the test vineyard these condition, particularly the cold evening wind, influenced the growth of the vines and the lenght of season.
When we planted the vines we put up a 7 foot high deer fence around the vineyard but there was no other barrier to keep cold air out or to divert it around the vineyard. So in the evening the cold air would come down the mountain and it would spill off the road and into the vineyard clearing and get trapped there by the trees around the vineyard. And the low spot that the vineyard was in allowed the cold air to settle in.
We noticed the first few years that we were prone to late spring frosts and early fall frosts so we cleared the trees around the vineyard to allow the cold air to drain away. That is when we learned the test vineyard was in a low spot and while clearing the trees did help a bit it would not help considerably for draining cold air.
So next we put up a 6' high wind fence along the road and that has worked excellent at diverting the cold air that comes down the road and preventing it from entering the vineyard. We have since noticed more heat in the vineyard over the course of the growing season and less frost events in spring and fall. One thing that is quite telling is the condition of weeds that grow beside the road versus weeds growing inside the wind fence in the vineyard. Ferns are very suseptable to frost and we notice every year the ferns that grow ourside of the vineyard towards the road have been frost bitten and die way before those that are just on the other side of the wind fence in the vineyard which are still healthy and green weeks later. This is the clearest indication of the value of the wind fence in keeping cold air out. Of note, we had a terrible wind storm in September 2014 that destroyed the wind fence and a few days later experienced an early fall frost as we were not able to repair it in time. Without the wind fence to divert the cold air we were vulnerable again and got frost early that year.
A few years back we planted some pine trees along the road just outside the wind fence and they are getting high now and soon will replace the wind fence. We have let the shrubs grow to about 3 feet high now that the pines are getting bigger. We also planted some willows last spring to fill gaps between the pine trees. In a few more years these trees and shrubs should fill in and we'll have a natural wind break to keep the cold air out and wont have to rely on the wind fence any more.