Why is College Area Community Garden member Stan Wong so intent on putting two sticks together? Pretty much any grape will do fine in San Diego's balmy climate, so what need is there of the ancient art of grafting?
First, size. Some vines are "petite," so that a 6-foot wide canopy from 3-feet tall to 6-feet tall is plenty of room. Other vines are so vigorous that they can climb to the top of a 10-foot trellis and create — every year — hundreds of square feet of productive canopy, masses of green leaves, and 50-100 pounds of fruit. After five years, the petite vines still have a slender half-inch diameter trunk, but the big vines can have a trunk as big around as your arm.
Here in San Diego, I use Centennial and Triumph rootstocks to make big overhead trellis vines, and Dog Ridge for planting in sandy soils. Petite vines needing grafting include Wapanucka, Diamond, Delaware, Seneca, Emeryville Pink, and the new wine-grape Aromella — all petite vines, all well worth the trouble of grafting.
Second, fussiness. Some vines, like the notoriously finicky heirloom Iona, a pink melt-in-your mouth grape named after an island in New York's Hudson River, with a taste like fruit cocktail syrup, are unhappy unless they have soil exactly to their liking. Iona is well worth growing, but it's a much better bet to put it up on an adaptable rootstock.
Third, as newly acquired vines are evaluated, sometimes a vine just doesn't have the fruit quality or disease resistance to justify its presence in the vineyard, but the trunk and roots are sound. In that case, it makes sense to graft over each arm of the mature vine to a single arm of a smaller-growing variety, one that is known to produce good fruit in San Diego County.
The grafting process is simple enough, although it takes years to get really good at it. For the wedge-cleft graft, the first graft all beginners learn, it is only necessary to cut the rootstock at a convenient height and split it down the middle using the knife like a meat-cleaver; whittle down the scion into a flat-sided wedge; put the wedge into the cleft, carefully matching cambium layer to cambium layer; wind the graft with tape, and coat all exposed grape-surfaces with a blob of hot grafting wax — which is just beeswax formulated with enough linseed oil to make it workable. Then, one or two months later, the gardener will either see a living sprout or a dead scion on top of the rootstock.
Recently, we did three "bench-grafts" (grafts onto unrooted rootstock cuttings) of Wapanucka onto Concord rootstock at the community garden in early February 2020. If they take, we will be able to pass out a top-quality heirloom grape on a strong, vigorous rootstock.
—Mark Miner is a highly experienced vinologist who volunteers a huge amount of hours at the College Area Community Garden as well as other gardens in the San Diego area. He is known for wanting to plant beautiful vines and flowering cacti on every square inch of land possible.