Just a quick note about late season frosts, while they're happening in Niagara. In New Zealand, early season frosts are a common problem, but not so much late season ones. I've already written about the use of wind machines in the dormant season (Aug14), but this season Niagara is in the situation of having many grapes (Chardonnay, Riesling, Cabernet franc, Syrah...) still out on the vines, and yet temperatures are dipping to below zero.
One reasonably strong frost event can kill all the green leaves on the vines, which means that the ripening process effectively stops (a small amount of sugar may accumulate in the berries due to the vines dipping into their carbohydrate reserves, which isn't good for long term vine health, sugar concentration may increase due to berry shrivelling, and then there may be small changes to acidity and flavour). Leaving the fruit on the vine won't help when you're trying to make normal table wines (icewines are a special case!), and if the vine tries to push a bit more sugar into the fruit using its reserves, it will be less resistant to cold temperatures during the winter, and may suffer a bit in the early season following.
So the fruit has to come off, ready or not!
To prevent the leaves from making an early departure, the wind machines can be used (providing there is an appropriate inversion layer) to keep the temperature dipping below zero, and keeping the leaves on the vines so they can photosythesise a bit more, hopefully ripening the fruit.
Even though the daytime temperatures are cool at best right not, there can be a significant amount of activity in the vines and fruit if it's sunny. The sun's radiation can heat fruit and the leaves to above the air temperature, so enzymes can be rockin' along quite nicely if it's not overcast or too windy.
Ironically, clear skies and lack of wind are exactly the kind of conditions under which frosts form, so what you want during the day isn't what you want and night!
We're keeping our finger's crossed for still air and sunshine during the day and clouds and a gentle breeze at night!!
One reasonably strong frost event can kill all the green leaves on the vines, which means that the ripening process effectively stops (a small amount of sugar may accumulate in the berries due to the vines dipping into their carbohydrate reserves, which isn't good for long term vine health, sugar concentration may increase due to berry shrivelling, and then there may be small changes to acidity and flavour). Leaving the fruit on the vine won't help when you're trying to make normal table wines (icewines are a special case!), and if the vine tries to push a bit more sugar into the fruit using its reserves, it will be less resistant to cold temperatures during the winter, and may suffer a bit in the early season following.
So the fruit has to come off, ready or not!
To prevent the leaves from making an early departure, the wind machines can be used (providing there is an appropriate inversion layer) to keep the temperature dipping below zero, and keeping the leaves on the vines so they can photosythesise a bit more, hopefully ripening the fruit.
Even though the daytime temperatures are cool at best right not, there can be a significant amount of activity in the vines and fruit if it's sunny. The sun's radiation can heat fruit and the leaves to above the air temperature, so enzymes can be rockin' along quite nicely if it's not overcast or too windy.
Ironically, clear skies and lack of wind are exactly the kind of conditions under which frosts form, so what you want during the day isn't what you want and night!
We're keeping our finger's crossed for still air and sunshine during the day and clouds and a gentle breeze at night!!
No comments:
Post a Comment