Issue link: http://read.dmtmag.com/i/37334
Twin leaders fill canopy QUICKLY W The twin-leader system results in a tall, thin, uniform canopy that opens up possibilities for mechanization. by Geraldine Warner he’s planting trees three feet apart and growing the trees with two leaders 18 inches apart on the trellis. Fuller said that’s cheaper than doubling the number of trees planted, and the three-foot spacing in the row allows him to control weeds with an in-row tiller, which would be difficult with closer plantings. A mulch for weed control is not an option because it provides habitat for mice. There are various ways to develop a twin-leader tree. For a 2008 planting of Minneiska (trade name SweeTango) on Geneva 11 rootstocks, Fuller bought whips, headed them low, and selected the two strongest shoots to grow up as the leaders. For more recent plantings, he used nursery trees specially grown with two leaders. Dale Goldy, a partner in Gold Crown Nursery in Wenatchee, said that even before he heard about the Bibaum system that is becoming popular in Europe he had been looking for better ways to develop a twin-leader tree—to avoid having to regrow the tree in the orchard and lose time developing the canopy. The Bibaum involves double-budding trees in the nursery so they already have two leaders when delivered to the grower. However, with double budding, there’s the risk that one of the buds won’t take, Goldy said. Nurseries had poor bud take last year because of winter damage from record low temperatures in November. If he had double-budded trees, it’s likely many would have failed. Some nurseries would have a market for trees where only one graft took, rather than both, but Goldy said his business comes mainly from custom orders. Two shoots Another way to grow a two-leader nursery tree is to train two shoots from one bench graft in the nursery, supporting each of the shoots with bamboo sticks. Goldy said that he first tried growing up the top two branches as leaders, but they were usually dissimilar in size. Now, he selects two similar-sized lower sprouts as leaders, although shading of one tree by another can still cause uneven growth. A twin-leader nursery tree—whether double budded or grown from a bench graft—is more expensive than a standard nursery tree because of the additional labor at the nursery, but it is still more economical than buying twice as many trees, Fuller noted. “Even if your cost per tree goes up, it’s not double,” he said. “When you plant 2,000 trees per acre and you’re paying full price, it gets to be a big number.” 42 AUGUST 2011 GOOD FRUIT GROWER Ray Fuller (left) and Andrew Del Rosario discuss a twin- leader block that Fuller planted in 2008. The trees were whips, which he headed back at planting so he could develop two leaders as the trees grew. The trees are Minneiska (trade name SweeTango) on Geneva 11 rootstocks. Tom Auvil, research horticulturist with the Washington Tree Fruit Research Commission, said that with the twin-leader system both lead- ers tend to be calmer and more productive than a single-leader tree because the vigor is divided between the leaders. The twin-leader system www.goodfruit.com hen organic grower Ray Fuller replants his orchard, he has two major economic factors to address. One is how to get the trees to fill their space quickly in order to generate optimum yields, and the other is how to effectively control weeds without herbicides. In recent plantings at his Chelan, Washington, orchard,