Does extreme cold damage vines in their dormant phase...?
Freezing vines – ask Decanter
Edward Hylton, Surrey, UK, asks: Will extreme cold events damage vines in their dormant season? I’ve been following reports about the severe weather in New York State.
Timothy E Martinson replies: Yes, extreme cold temperatures can injure grapevines – buds can even freeze.
The temperature at which this happens varies according to the grape variety and the time during dormancy.
For Vitis vinifera grapes such as Riesling, Chardonnay, Cabernet Franc and Pinot Noir (all grown in New York State’s Finger Lakes), temperatures that can cause bud injury in early January tend to be -21°C to -23˚C.
We had significant injury in 2004, 2005, 2015 and 2016, but January lows this year have been -17°C to -20˚C, so we aren’t too worried.
During damaging temperatures, growers slice open buds to see what percentage are dead.
If more than 20% bud death is noted, growers adjust their pruning by leaving more buds to compensate.
This works as growers typically prune off 90% of dormant buds.
Other ways growers cope is to have several trunks on each vine (they renew trunks every few years) or by mounding up dirt over the graft union (‘hilling-up’) to protect scion buds so they can train up new trunks.
Timothy E Martinson is senior extension associate at the School of Integrative Plant Science’s Statewide Viticulture Extension Program in Geneva, NY. This question is taken from Decanter magazine, subscribe to Decanter here.