Northern grape growers who refuse to restrict themselves to cold-hardy grape varieties can choose from a number of protection techniques in use around the world. Each method has advantages and disadvantages. The grower must determine the formula best suited to their own vineyard conditions. Or you can grow vines in your greenhouse.
Burying Vines To Protect Grapes
To be effective in cold climates vines must be covered with a minimum of 8 inches (20cm) of soil; 20-24 inches (50-60cm) in areas with little snow cover. The mound of soil should be spread out into the row, around 30 inches (75cm) to each side of the vine. Keeping the mound fairly wide protects shallow roots that project out into the row.
Another method makes use of a grapevine burial trench as soil piled at ground level is still much colder than soil below ground level. In the fall, carefully remove the dormant vine from the trellis. Prune the vine for manageability and cover the vine with old blankets or burlap.
The vine/blanket combination may then be wrapped with a fine wire mesh such as the insect screen used for windows. The screen will keep mice from eating the vine’s buds. Lay down the wrapped vine in a shallow trench lined with sand. Slope the trench down and away from the vine to prevent the accumulation of standing water.
Cover the vine with more blankets or rigid styrofoam insulation and then with a large piece of black plastic. Keep heavy winds from destroying your protective cover by fastening the plastic with long soil anchors, burying the edges with soil or holding the plastic down using boards or rocks.
Covering Vines To Protect Grapes
Another method of protection is to roll a geotextile fabric down a row of vines in the fall. This method works best in low head-trained vines as line posts installed between vines that are trained higher interfere with the process. The edge of the fabric is held down at ground level using soil, anchoring pins or wire hoops.
If vines are trained to stakes they may be pruned short, wound with geotextile fabric and secured with clips or twine. An additional layer of plastic sheeting can be placed over top as further protection against the wind and desiccation. Leave a hole at the top of the plastic to allow for the escape of excess moisture.
A single layer of horticultural insulating fabric (floating row cover) can give up to 10 degrees F (5.6C) of frost protection, depending on the product. Wrapping the vine in several layers will give added protection.
Straw is a good insulating mulch until it gets wet so is best applied in areas with dry winters. Keep in mind that mice may make nests in the straw and eat the vine’s buds.
Shredded cornstalks are water-resistant and maintain their insulating properties in the rain. As an added bonus they are too coarse to serve as mouse cover.
Sawdust that is baked or well-composted also makes good mulch material.
Deep Growing To Protect Grapevine Roots
A thick snow cover is the best insulator. In cold areas where it doesn’t snow the vines will freeze deeply and roots may die. According to Northern Winework, establishing a vine using deep ditch cultivation can manage or eliminate root injury and death. The following method has been used in Inner Mongolia where winters are cold and extremely dry.
Prepare the growing row by digging a ditch 4-5 feet (1.2 to 1.5m) wide and 3 to 4 feet (0.9 to 1.2m) deep. Plant vines in the bottom of the ditch. As the vines grow, fill in the ditch with soil. This method takes time, usually 3 years to fill the ditch to the top, but keeps the main root system very deep. Temperatures at such depths rarely drop below 0 to 5F (-18 to -21C) ensuring the roots are in little danger of winter injury.
This method is most effective in areas with low groundwater levels of about 20 feet (6.2m); any higher and there is a risk of flooding the roots with water. To try this method in areas with a high water table, placing a drain tile pipe in the bottom of the ditch is recommended.
In the spring when buds begin to swell in hardy vines, it is time to uncover or unearth protected vines. Mulch can be pulled away from the vines and worked into the soil to provide organic material.