Oregon State University extension agent Lynn Long, who is based in The Dalles, said Regina is known as “a reluctant bearer” and what’s puzzling is that it sets less fruit in what growers would consider good pollinating conditions (when the weather is warm) than in cool weather.
He estimates that a five- to seven-year-old Regina block on Gisela 12 rootstock would typically yield three to six tons per acre compared with five to eight tons from a similar Bing block.
However, during a recent visit to Chile, Long found that growers there are planting a lot of Regina and report no problems with fruit set. They like the variety because of its resistance to cracking and because they can deliver it to China—their big new market—in very good condition.
“They’re shipping 80 to 90 percent of their crop to China, and they’re getting good prices,” Long reported to growers during the annual OSU preharvest cherry tour in The Dalles in June. “They’re finding it’s a big cherry, and it arrives in Shanghai, or wherever they’re shipping it to, in really good condition.”
Regina originated in northern Germany where spring weather is typically cool, and it may be that growers in cooler growing regions don’t see the yield deficiencies that growers in the Pacific Northwest do, he said.
During bloom, after a pollen grain lands on the flower stigma, a pollen tube begins to form. Pollen tubes are channels that grow down the style to the ovules. Pollen grains travel down the tubes to reach the ovules and fertilize them.
Long said research has shown that Regina has a very short ovule longevity, which means that if the weather is warm, the ovule could die quickly before the pollen tube has had time to reach the ovule.
Dr. Matt Whiting, horticulturist at Washington State University in Prosser, said scientists believe that the growth regulator ReTain (aminoethoxyvinylglycine), which is an ethylene inhibitor, can slow the senescence of the ovules, thereby extending the window of opportunity for fertilization. He has been doing trials in collaboration with growers in Australia who also grow Regina. To avoid problems with poor fruit set, they apply the equivalent of one pouch per acre of ReTain during bloom.
“They recognize the expense of doing it—for us, it’s about $400 to $500 per treatment—so you’ve got to get something out of it,” he told the Oregon growers.
Australian growers find they can boost their yields by an additional ton or two per acre.
At the orchard of Tim Dahle in The Dalles, Long is conducting a trial to assess if ReTain could provide the same benefits as seen in Australia. He is comparing several treatments: one pouch per acre at the popcorn stage of bloom; half a pouch, one pouch, or one and a half pouches at 10 percent bloom; one pouch at 50 percent full bloom; and one pouch at 100 percent full bloom.
Because the weather was cool during bloom this year, fruit set is good even on the control trees, he said. “I can’t see with my eye that there’s much difference.”
However, differences might become apparent at harvest when the fruit is counted and measured, he said.
Whiting said a sister trial is being conducted in Washington in collaboration with grower Rick Derrey at Zillah. Natural fruit set there this year was lower than in Oregon, so he expected to see more effects from the ReTain treatment.
Long said Kordia (marketed in the United States as Attika) is often used in the Pacific Northwest as a pollinizer for Regina, which is an exceptionally late blooming cherry. Kordia blooms earlier than Regina, which is not necessarily a bad thing unless the weather is warm and then cools down, widening the window between bloom of the two varieties.
For a variety with short ovule longevity, the pollen should be there when the blooms are starting to open up.
Sam is the best pollinizer for Regina, Long said. “But the problem with Sam is the fruit is lousy—I don’t know if you’ve ever tasted Sam—and not worth picking.”
Schneiders blooms a little earlier than Regina, so has the same issues as Kordia. Heldelfingen will work, but the fruit is not marketable. Stark’s Gold has a long bloom period.
“There just aren’t a lot of good quality cherries, except for Schneiders and Kordia, that work and you can harvest the crop and sell it as a fresh cherry,” Long concluded, although Benton and Skeena, which both bloom a little ahead of Regina, are possibilities.
Asked about the recommended number of pollinizing trees, Long said that in Chile growers plant two rows of Regina alternated with two rows of Kordia so that there’s a pollinizer next to every Regina tree. A downside is that the bees tend to work down the rows of trees, rather than move across rows, Long said, but it might be a better approach than taking up space in the Regina rows with pollinizer varieties that won’t be picked.
Mike Omeg, a grower in The Dalles, said he likes the idea of the alternating rows. Currently, he has three pollinizer varieties—Sam, Kordia, and Stark’s Gold—planted crab-apple-style in every row of Regina. Those varieties typically mature before Regina, so he lets the fruit drop to the ground. “I’m not about to enter my block and beat up the Reginas to pick pollinizers,” he said.
Omeg has found that increasing the number of bees helps improve Regina set. He puts five hives per acre in the Reginas and leaves hives that have been pollinating other varieties in the orchard until the Reginas have finished blooming. He’s also planted insectaries with native blooming plants to attract feral bees and native bees, such as mason and bumble bees, to the orchard.
This year, with a naturally good set on Regina because of cool pollinating conditions, it probably won’t make a difference, he said. “But in the average year, it does help.”
Asked about pollen inserts, Omeg said his father, Mel, once tried them. He saw no improvement in the crop, and when he looked closely, he concluded that the bees were just taking the pollen into the hive rather than distributing it in the orchard. “That’s probably true,” Omeg said. “Bees are pretty smart.”
Long asked if it was worthwhile to grow Regina, with all the difficulties involved.
“Besides blush varieties, like Early Robin, it’s one of the most profitable varieties,” Omeg responded. “It has a high packout and high net income per acre. It’s a challenging variety, but I think it’s worth it if you can pay attention to all the details and not make any mistakes. It’s an unforgiving variety as far as mistakes.”