After a week of very low temperatures (down to -6 degrees Celsius one night) and some great photos from Klaus showing a white Glenguin, I thought a few words on vines and frost might be interesting. So here goes:
1. The vines are in winter dormancy, having a rest and are not damaged by frost at this time.
2. Frosts in spring are bad news. Indeed in 2001 a “hanging” frost in early September killed all the Semillon green shoots.
3. In 2001 we lost all the Semillon crop and the frost damage was so severe that some vines whose trunks had split had to be cut close to the ground and retrained back to the wire. Backbreaking work…
4. In spring the damage occurs when the rising sap freezes, causing the cell walls to rupture. This damages shoots, leaves, buds and even vascular tissue.
5. There are 2 main frost types. Radiation frost occurs on clear still nights, with low humidity. Rapid heat loss from the ground results in an inversion layer of cold air that may extend 10-20m above the ground.
6. Advection frosts occur when wind chill causes temperatures at the vine surface to fall. This usually occurs when a cold mass of air moves up from Antarctica.
7. In order to minimise risk at Glenguin we use a high trellis and hard cane pruning to minimise damage. We do not use any sprays, fans, oil burners or helicopters as a sustainablility practising vineyard.
8. This means we are at danger from frost and sometimes it reduces yields and damages vines. Wine is a natural agricultural product and sometimes we suffer the consequences.
