The new vineyard was developing right on schedule until we were hit by a late season frost on April 29th. Temperature at the bottom of the hill fell to 30.6 degrees.
In the picture on the right you can see where the vegetation stops. On the left is a close up of a damaged rootstock.
This year's frost strategy was to rely on the 20" white grow tubes to protect our young vines. Earlier this spring before they started to push buds we pruned the vines back to about 8 inches of wood and put them in grow tubes.
The grow tube strategy was working. A vineyard check after the frost (31.6 degrees) on April 16th showed only a few leaves nipped by the frost. This frost was followed by warm weather and the vines really started to develop until the morning of the 29th when we saw a 30.6 degree frost.
My theory on why the tubes didn't protect the vines is: The shoot development in the tubes during the warm weather brought the shoots and leaves in contact with the sides of the tubes. The cold was transferred by contact and was sufficient to kill the primary bud push. The secondary buds are now starting to push. If we had turned on the frost protection system ( micro sprinklers), we probably would have raised temperatures by 1-1 1/2 degrees and damage would have been limited.
The bottom line is that about 1/3 of the vines will have retarded growth this year and may not be ready for grafting until the fall.
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