Harnessing Nature For Frost Protection

It’s vine-bud-developing / frost-watching time.  This is the season of torment when we become obsessed with our ever increasing weather indicating gadgets – checking highs, lows, wet temperature, dry temperature, humidity, dew point and so on.  Once the buds develop beyond the ‘woolly bud’ stage and particularly when things are looking lush and green, if a frost strikes it can be devastating and the crop can be obliterated entirely.  Usually the frost will only take a proportion of buds and secondary buds can make up some of the loss, however if there is a frost after the secondary buds develop, then it’s all over.  The sinking heart feeling of watching a lush green haze on a vineyard turn brown is a reality many grape growers face.   Vines are tending to develop earlier in the season to compound the issue and frosts are striking more frequently and with more extreme low temperatures in recent years.  To add to the excitement and unpredictability, East Hendred seems to have a microclimate beyond the realms of any weather forecast in the area.  

Mitigating such forces of nature requires innovative thinking.  Growers have experimented with many tactics; the main ones are:  Bougies (paraffin candles) which can be laid out over the vineyard raising the temperature a little, but these are expensive and labour intensive; they do create a rather magical scene at least.  Alternatively, large propane burners can be used to pump hot air underneath vines. Or wind turbines used to draw the warmer upper layers of air downwards, so the cooler air near the ground is moved upwards.   Helicopters are sometimes employed by vineyards to do this too – they love this in Napa Valley.

There is another method which craftily uses the energy dynamics of water transitioning to ice to protect the buds.  So long as a constant stream of water remains coating the buds and freezing, the buds remain protected and do not freeze inside this ice cocoon.  In years gone by, the MacKinnon family and Biagio who used to look after the vines here, sprinkled the vines with water from a tractor spray, but as frosts are getting more severe and frequent, it is just not sufficient (and tractor noise not ideal in the middle of the night.)  But the concept is too appealing and our natural resources too ideal not to harness the power of it.   Given Hendred vineyard has a pond into which water drains naturally from the land all year round, and several springs also, automating a sprinkler system with pumps which are mostly powered by existing solar generated electricity is being tested this year.  With novel sprinkler heads which use a pulse action to make sprinkling ultra-efficient, it is the newest and greenest method available to us.   So the system has been installed, with much head-scratching and adaptation of components along the way. The sprinkler heads spurted rhythmically on a sunny afternoon for a few hours anyway; whether it endures several hours on a frosty night remains to be seen.  I have poured the Holy Water kindly given out at the Easter service at St Mary’s into the pond as a fall back.

So the next time you see Helen Willets or Tomas Schafernaker on the BBC gesticulating over blue and white bits on the weather map and you see ominous minus symbols, spare a thought for us as we will be attaching head torches to our woolly hats, flicking sprinkler nozzels and getting ready to be soaked changing pump filters in the dark.