Cold as Ice

„April showers bring May flowers“, they say. Well, April has mainly brought us sunshine with temperatures up to 30°C so far. Knowing that it's April, I am not surprised that yesterday, I had to dig out last year's sunscreen and today I am back in my winter coat with an umbrella in my hand.

The warm temperatures this spring have untimely woken up the vines from their winter rest and together with the abundant precipitation over the winter and early spring, vegetation is about three weeks ahead of normal.

The crispy young shoots at this time of the year are a special treat for the deer but the tension among the growers is palpable. A single night of temperatures below zero could destroy a major part of the crop at this stage.

It's around full moon that the danger of frost is the greatest. Cold nights with clear skies and early morning temperatures dropping below zero degrees are disastrous for the young shoots.

There are ways that wine growers can (try to) protect their vineyards from frost damage but it takes consideration and experience to choose the right measures.

Not every method is suitable for every vineyard topography, grape variety or meteorological condition. Drift freeze, which is icy cold airstreams blowing through the rows requires different measures than radiation frost that typically occurs on clear nights with little or no wind.

In practice, only antifrost candles are feasible measures in most vineyards- but can hardly be installed in all vineyards at the same time. Frost irrigation is not commonly seen in vineyards here and helicopters that could help prevent radiation frost damage by mixing warm and cold air are hardly available and affordable for most winegrowers.

What we can do during the time of frost dangers is keep the cover crop well trimmed. Short cover crop can raise ground temperatures by up to 2°C compared to vineyards with higher cover crop.

Nevertheless, all these measures are not much more than a nice but desperate attempt to avert disaster.

Next full moon is April 23rd. Keep your fingers crossed for us, it will be very close this year…