Vines are currently being pruned all over the country (and the world) at this time. Minnesota has been blessed with some (relatively) warm days this week, which have made for some pleasant pruning weather for those out in the vineyards. Compared to last week, with temperatures hitting -20 F (-29 C), this week’s temperatures in the 40’s F (5 C) feel quite warm. The snow is starting to melt, and the need for snowshoes in the vineyard has passed (for now).
However, it’s last week’s low temperatures that should be highlighted for the purpose of this article. It is these extreme temperatures that make it impossible for us to plant V. vinifera vines in Minnesota (without winter protection), as the buds would die at -3 F. That’s not to say that hybrid vines are immune to winter injury, though.
If you haven’t started pruning yet, now would be a good time to assess the winter bud injury in your vineyards so that you may compensate by leaving extra buds during pruning. If not, you may be in for a surprise come spring when you fail to see those lovely green leaves starting to emerge.
Some winter injury is normal, even in northern regions that have been growing grapes for years. However, if you’re seeing winter bud injury that is greater than 20% on a regular basis, you should reassess your site selection for your vineyard, or the varieties you chose to plant (not all “cold-hardy” varieties are equally hardy). You should also start to look at what you did in the summer months to start to prepare the vines for winter. Remember that after grapes reach veraison (color change), the vine is already starting to prepare for winter. Vine stress (such as delayed harvest), drought, and over-cropping can all reduce a vine’s potential cold-hardiness.
In the end, some sites just aren’t a good place for growing a vineyard. Scandinavians as well as the British learned this lesson a long time ago and have been successfully making fruit and honey wines for ages. Even in the northern areas of France hard cider is more prevalent than wine… and there is certainly nothing wrong with that!
|Minnesota Vineyard – www.flickr.com/photos/monicaraemn|
For further reading:
Zabadal, T., I Dami, M Goffinet, T. Martinson, and M. Chien. 2007. Winter Injury to Grapevines and Methods of Protection. Michigan State University, Extension Bulletin E2930.
Pool, R. M. 2000. Assessing and Responding to Winter Cold Injury to Grapevine Buds, web page, Cornell University.
Walter-Peterson, H. 2010. Bud Injury Testing, two-part video. Finger Lakes Grape Program’s YouTube channel.
Martinson, T., S. Hoying, H. Walter-Peterson and J. Creasap Gee. Bud Hardiness Page, Viticulture and Enology Outreach page, Cornell University.