Grafting is a process by which two grape plants are combined to create an improved single vine with new desired attributes. Grape vines are grafted to either convert the vineyard to a variety that is anticipated to receive high premiums, or to eliminate a variety for which there is little to no demand.
The two most common grafts for grape vines are combining a local bareroot with a new variety of fruiting vine, and combining a new fruiting vine with an old fruiting vine's established stump.
For the greatest success when attempting a graft, cut the grafting wood during the dormant season, and do that actual grafting in the later part of February. Store the wood in dampened paper towels at a temperature between 32-36 degrees. Grafting is a challenging process, and success is not guaranteed on the first try, but with some practice, it can be accomplished with up to a 90% success rate.
Saw off the old vines. For the best results, saw off the vines before the bark begins to slip and then re-cut the grafting point once it is time to combine the two plants.
Make a saw cut on the side of the vine if the vine is bleeding sap. This cut should only be 1/4 inch deep.
Use the wedge knife to gently cut below the bark on the desired vine. Cut a second cut about 2 inches below the first to form a bark pocket.
Prepare the scion for grafting by making a clean cut with the scion knife. Avoid sawing the scion, as this will damage the bark cells. Instead complete the cut in one smooth, downward stroke. The cut should be diagonal; create a pointed edge.
Slide the pointed edge of the scion into the bark pocket and point the buds in the direction that growth is desired.
Paint a thick layer for grafting compound around the entire graft area. Be sure to get all angles completely and thoroughly covered. For best results, consider re-painting an hour later to ensure no spaces were missed.
Observe the growth of the grafted plant and train the new shoots as they emerge.