Field-grafting grapes not a sure thing
Conditions must be just right when field-grafting grapes in cool climates.
Dick Boushey shows a cleft graft that he used to change a block of Semillon wine grapes over to Sauvignon Blanc.
Field grafting wine grapes has successfully been done in Washington State. However, grape growers attending a Washington State University viticulture and enology field day learned it’s not a sure thing, and high percentage takes are very dependent on timing and weather.
Grandview, Washington, grape grower Dick Boushey of Boushey Vineyards shared his successful and not-so successful field grafting experiences during the mid-August field day sponsored by the Washington State Grape Society. He showed growers and winemakers a two-acre block of Semillon grapes planted in 2003 that were grafted earlier this spring to Sauvignon Blanc.
Boushey said he was motivated to field graft after being impressed with grafting done by Steve and Todd Newhouse on 75 acres at Snipes Mountain, near Sunnyside. The following year, the Newhouses picked half a crop using a mechanical harvester. “That’s what influenced me. But little did I know that no one’s been able to duplicate that success.”
Three years ago, Boushey grafted ten acres of juice grapes to wine grapes and was pleased with the results. But in his most recent grafting, he estimated he had only about a 60 to 70 percent take, and was even less successful in a small Merlot-grafted block that had only a 50 percent success rate.
“You need to have everything right to be successful,” Boushey said. He thinks this year’s cool spring weather limited his success and he should have waited a few more weeks for temperatures to warm up before grafting. “We often do it too early. We need to wait until the end of April or into May to get through the cooler weather so that temperatures are around 60°F, because that’s when the bark starts slipping.”
He adds that scion wood must be in good shape, kept cool, and still be dormant. Young vines are better candidates than older ones, and some varieties graft easier than others. Also important, the scion or bud wood should come from a certified source and be tested for viruses.
He prefers the cleft graft, a technique that uses two face cuts on both sides of the trunk, matching diagonal slices of the scion wood into the cuts and then taping and gooping the graft. Workers must “bleed” the vine every three weeks by making a slice through the cambium layer to prevent the sap from pushing out the new graft union.
Boushey places the height of the graft union 24 to 30 inches above the ground so that the vine reaches the wire quickly and can be tied (wind often breaks the graft union if it isn’t secured). The higher placement allows him to farm as if the vineyard is an existing one and also helps protect the graft union from cold temperatures.
Another tip he gave was to leave extra suckers on the main trunk below the saw cut, removing the suckers after the graft union has callused and healed. “You have all this root system under the ground and below the graft, and there’s a tremendous amount of surge coming up. The suckers help diffuse that.”
Boushey said he has about $1.75 into each vine, a cost that includes cutting down the vine trunks, the $1.25 per vine fee charged by the commercial grafting company, and labor to bleed the grafts several times. “With grafting, you don’t have nursery costs, training costs, and you can be back in production by the next year. It might not be worth it if it doesn’t work, but if you can do it successfully, grafting really pays off.”
Costs for dormant, self-rooted, certified vines produced by an in-state nursery can range in price, depending on quantity, from $3.50 to $1.75, not including royalties.