Shinji Kawai with a haskap variety that breeder Maxine Thompson named after him on his farm in Brownsville, Ore.

Some people take up new projects in retirement. Golfing, say, or restoring old cars. But for plant breeder Maxine Thompson, retirement from her position as a professor of horticulture at Oregon State University offered the chance to focus on a pet project she’s been involved with for many years: haskap berries.

Haskap berries are the edible fruit of Lonicera caerulea, a honeysuckle native to northern boreal forests in Asia, North America and Europe. The extremely cold-tolerant plants produce a deep purple, tangy-sweet berry said to provide a concentrated dose of health-promoting antioxidants.

Maxine began working on haskap in 2000, initially concentrating on varieties from Siberia. “I first evaluated 35 Russian varieties,” says Maxine, “and none of them are any good. They’re small, and they bloom too early, when the bees aren’t out. They’re not suited for this climate.”

Then, a friend passed along a single haskap bush somebody had brought him from Japan. She planted it out, and it bloomed a month later than the Russian varieties. “And the next year,” laughs Maxine, “I went to Japan, and got seeds from eight different sources.”

Today, Thompson works exclusively with cultivars from northern Japan, which she says have a superior flavor and berry size to varieties from Russia, as well as better adaptation to moderate coastal climates.

Thompson’s initial plantings were in fields at OSU, but in 2008, she decided to take her plants home with her. Trouble was, she didn’t have space for all her bushes — so she reached out to Shinji Kawai, a former student and current faculty research assistant in OSU’s Department of Horticulture.

Unlike most Americans, Kawai was already familiar with haskap berries from his native Japan, where they’re harvested and used as a popular ingredient in ice cream, tea and other processed products. Intrigued by the project, he said yes, and dedicated a half-acre of his Brownsville property to the berry.

Since then, he and Thompson have worked closely, working together to grow out selections and evaluate varieties.

They’re looking for traits like yield, flavor, disease resistance, upright habit, a large and firm berry and a dense fruit set pattern.

“It’s been very exciting to be able to work with her,” says Kawai.

So far, the fruit is still too soft and irregularly dispersed for machine harvesting, which means harvest labor costs are a significant barrier to widespread commercial adoption.

Yet Thompson and Kawai have made great strides in flavor and berry size, with some crosses producing 2-gram berries of 16-18 brix, almost twice the brix of the average blueberry. “The taste is just marvelous,” says Thompson.

Today, 90-year-old Thompson is still engaged in the breeding project, making selections and crosses from her plants and Kawai’s plants. Several of her cultivars have seen commercial release, including four varieties through Spring Meadow Nursery. In the next year, she plans to release an as-yet-unnamed cultivar with exceptional berry size and sweetness, also through Spring Meadow Nursery.

Some local food producers are also experimenting with the berry, including Portland-based Stonebarn Brandyworks, which recently released a haskap liqueur.

Thompson and Kawai think there’s much more work to be done, including more marketing to introduce American consumers to the fruit, as well as continuing their search for more favorable bearing traits. “That’s what breeding’s all about,” says Kawai. “When somebody really has a keen observation, they know how to do the selection process, the breeding process, crossing process, then maybe they can find something extraordinary.”