Sweet cherries in high tunnels
Local cherries without cracks are highly prized by eastern consumers.
Tunnels offer little protection from frost, but they do keep rain off. This reduces rots and prevents ripe cherries from cracking
Molly Brumbley had never grown tree fruit when she planted sweet cherries in the spring of 2005. That fall, she built the steel structure to cover them with plastic the next spring—a highly innovative move at the time—and now she ranks as one of the most experienced growers in the high-tunnel fruit business.
Good Fruit Grower interviewed her on April 3, catching her when cherries were just starting to bloom at the farm in Elkton, Maryland, and she was rounding up a crew to put the polyethylene skin on her two acres of Haygrove high tunnels. She has 900 trees growing in nine rows under three 28-foot-wide bays that stretch 900 feet long.
A careful planner and budgeter, Brumbley said the enterprise has worked pretty much as she penciled it out before she started. The sweet cherries ripen in June, just after the spring strawberry season ends and just before the raspberry and blueberries start. These four crops are the backbone of the direct marketing effort at Walnut Springs Fruit Farm.
The tunnels were built primarily for rain protection for the cherries and tree health, and they do the job. “We’ve had no problem with cracking,” she said. There are no sides on the tunnels. “Frost protection is not the reason we built these,” she said, and she doesn’t know whether she will get any such protection—or need it— this year when bloom came three weeks early.
Nor was season extension a primary goal, although the cherries have ripened about a week earlier than typical for the area, which gives them a competitive advantage, she said.
"Skinning" the tunnels could have been done earlier this year, given the early bloom. “You have to understand how we do things,” she said. “We have no permanent labor. We try to get the poly up during spring break, when we can get high-school kids and other local labor. It takes three or four hours a day for three days to get this done, and you can’t do it in the wind. We’ve had some human parachutes in the past.”
Haygrove’s high tunnels are steel structures, with hoops built atop five-foot-tall posts that form sidewalls. The 900-foot-long sheets of polyethylene, one for each bay, are stored in the off-season in the gutters between the bays, under black plastic to protect them from degradation by the sun. Then they are pushed up and over the hoops, using long poles with U-shaped forks at the end.
“Actually, we push a whole 900-foot roll to the top and fold it down both sides,” she said. They do that for each bay.
The cover is tied down with crisscrossed ropes in what Brumbley says is an ingenious system developed by Haygrove. The system is built to withstand high winds, but she tries to get the skins off before hurricane season comes in September.
Brumbley went to England twice to visit Haygrove headquarters and to see how English growers are doing things. She went to look at strawberry production and liked the idea of growing cherries under the Haygroves. She planted the cherry trees in three rows in a diamond pattern, six feet between rows and five feet between trees, with an alley along one wall of each bay wide enough for a tractor and airblast sprayer. Each row of trees is watered with a double line of trickle irrigation tubing, buried in the ground.
As the trees have gotten larger, she has found it more difficult to penetrate the three rows with spray. Last year was a hot, humid year. “It was 95 degrees, and there was no air moving when the fruit was ripe,” she said. “We had Botrytis and brown rot for the first time.” She thinks the foggy and rainy weather during bloom contributed to that.
She’s made some adjustments. She originally had close to 1,000 trees, and has taken out about 100 of the weaker ones. She topped the trees to bring them down to eight to ten feet and provide open space and air movement over the top. And she pruned the trees hard to open them up and also encourage fruitful wood.
Insects have been no problem. “We use no insecticides—none,” she said. “Japanese beetles don’t like the tunnels, apparently. Nor has disease been a big issue except for the brown rot last season. The trees are healthy with very little bacterial canker, and, without the foliage getting wet, cherry leaf spot has been no problem at all, and foliage is luxuriant late in the season.”
Birds were initially a challenge, but the Haygrove structure is easily netted. Netting is put up each year to shutter the ends, gutters, and sidewalls against bird damage.
Brumbley said she is grateful for the advice she has received from industry experts. Michigan State University horticulturist Dr. Greg Lang, who is studying production of sweet cherries in high tunnels, has visited her operation, and she keeps close tabs on his work.
Pruning and managing tree structure has been the biggest challenge. Lang is working on systems that keep trees narrow for good light penetration, leave stubs to prevent tree loss to bacterial canker, and encourage fruitful wood close to the trunk.
Right now, she says, she uses a modification of the method recommended by Lang, which has morphed into what she calls “the Molly method.” “My trees look really odd right now,” she said, having been shortened and pruned hard this spring. She does both dormant and summer pruning.
Retired Cornell University cherry breeder Dr. Bob Andersen visited several times and gave her advice on varieties and pollination. She uses bumblebees during bloom, which usually takes place under the covers. Those bees will stay in the tunnels and do the work. She planted all the trees on Gisela 5 rootstock and chose lots of varieties, both to boost pollination and reduce risk. She has Cavalier, Black York, White Gold, Attika, Hedelfingen, Benton, and Lapins.
“Attika is my favorite,” she said, “but the customers love the White Gold. My varieties were chosen based on winter hardiness, pollination compatibility, and timing of ripening. One of my primary concerns was tree survivability, and I am very pleased. “
Almost all the cherries are sold pick-your-own. “The customers love it,” she said. “Several years ago, they were picking inside during pouring-down rain, and they were grateful to us that we’d made it so nice for them. They loved the whole experience, and we charged a premium price.”