Frosts put the bite on Marlborough vineyards

In most forms of agriculture, spring is a welcome time of regeneration and rebirth. Lambs are born, fruit trees blossom, days start earlier and the sun shines longer. But for a viticulturist it brings a fresh set of headaches, especially in cooler climates like the South Island of New Zealand.

For Mark Ludemann, viticulturist at Lawson’s Dry Hills in Marlborough, it can be a time of 4am starts and often sleepless nights. Mark is responsible for overseeing the company’s vineyards in the Awatere and Waihopai Valleys, Rarangi, Ben Morven and also those closer to Blenheim. So as spring approaches and the vineyards come to life, Mark certainly has his hands full.  There’s the ever-present threat of frosts, all at a time when extreme weather conditions can do the greatest damage. “The vineyards in the valleys are most prone to spring frosts,” Mark explained. In 2018, bud burst began with the Chardonnay vines in the 2nd week of September, but as a cold blast blew in from the south during mid October, Mark was feeling nervous.

Frosts threaten to kill off the delicate spring buds reducing grape yields and can also affect the vine’s foliage which is vital for photosynthesis. So anything a Marlborough wine producer can do to minimise the impact of frost will pay off at harvest time. For centuries, European grape growers have used various forms of heating like oil-burning ‘smudge pots’ to increase temperatures at ground level. In modern times, however, large frost fans and even helicopters have proven to be more effective.

Lawson’s Dry Hills’ vineyards are equipped with frost fans which move warmer air down to ground level, which helps prevent moisture on the vines from freezing. Towering around 10 metres in the air and equipped with large aeroplane-sized propellers, frost fans are much like rescue helicopters when it come to protecting grape vines.

But frost isn’t the only concern. “Right now, we’re spraying for diseases like powdery mildew,” Mark said.  They also have to mow between the vines to keep the grass and weeds down, which can also help reduce the impact of frosts. Like many Marlborough vineyards, sheep graze between the vines for part of the year. But at the end of winter the sheep are sent off to conventional pastures, so vineyard managers revert back to traditional forms of mowing to keep the grass down.

Viticulturists like Mark can gain some comfort from knowing that the region is becoming warmer, with spring frost becoming less of a threat over time. Whether these warmer temperatures are the result of climate change or are caused by other changes in weather patterns may be a matter for debate but the region is certainly becoming warmer if meteorological records are any indication.

Data recorded at the Blenheim Meteorological station at Grovetown Park indicates that Marlborough is experiencing half the frosts it did 90 years ago. Back in the 30’s and 40’s, Blenheim shivered with up to 70 frosts a year. Compare this with 2017 when there were just 30 ground frosts during the winter, four frosts in September and none in October – the first year in which no ground frosts had been recorded. While the Awatere and Waihopai valleys are generally colder than Blenheim, the vineyards even in these valleys are experiencing fewer frosts than in years gone by.

Of course all will be forgotten come summertime when Marlborough sparkles as one of the sunniest regions in the country, and the new vintage wines once again prove ­­­­our distinctive sauvignon blancs, chardonnays and pinot noirs to be the toast of the wine world.

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