Dr. Maxine Thompson, a retired professor emeritus from Oregon State University, has dedicated her entire career to developing fruits and nuts for production worldwide.
Photos courtesy of Spring Meadow Nursery

You may not recognize her name, but Dr. Maxine Thompson has been studying and working in the horticulture field for longer than many well-known nurserymen have been alive. Described as a still-feisty, passionate scientist, Thompson has certainly left her mark in the world of plant science and genetics. Next time you pluck a ripe haskap berry and pop the delicious fruit in your mouth, remember this incredible woman.

At a time when a woman’s rightful place was considered to be at home raising children, Thompson was studying plant science and horticulture, earning her PhD in genetics at the University of California-Davis. In 1969, she became the assistant professor of horticulture at Oregon State University, the first woman to be appointed to a tenure-track position in that department. During her extensive career at OSU, she researched fruit breeding and genetics, floral biology, pollination, fruit set and cytological studies of fruit and nut species. She was also one of the founding scientists for the first clonal gene bank in the U.S. National Plant Germplasm System in Corvallis, Ore.

At the height of the research segment of her career in the early 1980s, Thompson became a consultant for the Food and Agriculture Organization of the United Nations and then for the U.S. Department of Agriculture. Her research on fruits and nuts took her to six southeastern Asian countries, Pakistan, Uzbekistan, Tajikistan, Kazakhstan, Ecuador, and the People’s Republic of China. As a result of her travels, she donated 645 accessions (seeds and plants) to the U.S. National Plant Germplasm System.

The final frontier: blue honeysuckle fruits

Her final expeditions in the late 1990s and early 2000s took her to eastern Siberia, Russia and to Hokkaido, Japan to obtain seeds of blue honeysuckle. You may have heard of berry bushes labeled “honeyberries” or “haskaps” (pronounced hz-cap). Though they are both cultivars of Lonicera caerulea, these blue honeysuckles are distinguished by their subspecies. Honeyberries were developed by Russian, and later Canadian, scientists from L. c. subspecies edulis and kamtschatica, which are well adapted to the extremely cold regions of Russia but not to more moderate climates. Those types of blue honeysuckle typically bloom too early in the northern U.S., often during warm spells in winter when pollinators are not available, and have much more bitter tasting fruit.

Cultivars of haskaps were first exclusively developed in the United States by Thompson from L. c. subspecies emphyllocalyx, which is native to northern Japan. Compared to the Russian subspecies, Thompson’s cultivars of Japanese blue honeysuckle are far better adapted to moderate climates like those found in the Pacific Northwest. They bloom in March and early April in western Oregon, when frosts are common, but the flowers can withstand temperatures of 15°F without damage. The flowers are pollinated mainly by bumble bees and mason bees which are active at lower temperatures. Most haskap cultivars need to be cross-pollinated to yield fruit.

Haskap fruit matures before or with the earliest cultivars of strawberries, typically in May and June in Western Oregon. The deep purple fruits are similar in color to blueberries, but range in shape from oval to oblong. In her breeding work, Thompson selects for a variety of fruit textures and tastes, from sweet fruits with high brix counts that taste something like a cross between a blueberry and a raspberry, to more tart varieties that are best used in baked goods, jams, and high end processed foods.

Japanese haskap fruits are larger and sweeter than cultivars developed from the Russian subspecies. The plant is also better adapted to moderate climates.

Unlike blueberries, the color of haskaps does not indicate their ripeness. The fruits turn blue as early as two to three weeks before they are ready to be picked, at a crucial time when the sugars are accumulating in the fruits. Those picked too early will be quite sour, but those picked when they are ready will fall off in your hand and are melt-in-your-mouth delicious. They have a very delicate skin and seeds so tiny you don’t even notice them.

From a nutritional standpoint, haskaps are considered a superfruit, containing more of vitamins C, A, and E than oranges, and three times the antioxidant level of blackberries. They are marketed as a health food in Japan, Russia, and northern China where they have been grown for centuries. According to Dr. Thompson, they have been known to have a therapeutic effect on cardiovascular and gastrointestinal diseases, to reduce blood pressure and even treat malaria.

Breeding haskaps for growers and gardeners

The goal of Thompson’s haskap breeding program is to develop superior cultivars that would serve as the basis for a new berry crop for the Pacific Northwest, which is well-known for producing some of the most delicious berry crops in the U.S. She is working to develop cultivars suitable for commercial production as well as cultivars better adapted for home gardens and small U-Pick farms. Because of the very thin skin on the fruit, mechanical harvesting is often out of the question, and the crops typically need to be picked by hand. This trait is not such a problem for gardeners growing haskaps as a fruiting hedge at home or for local farmers market vendors carrying them as a specialty product.

Yezberry Solo is one of the first named cultivars of Japanese haskap hybridized by Dr. Thompson. It is being introduced exclusively through the Proven Winners network in 2016.

Blue honeysuckle is extremely easy to grow in USDA Hardiness Zones 3-7. The hardest part is finding the stock. Thompson has recently been working with one of the largest shrub producers in the U.S., Spring Meadow Nursery of West Michigan, to introduce her first two named cultivars of haskap, Yezberry Maxie and Yezberry Solo, which are exclusive to the Proven Winners brand. The name Yezberry is a nod to the origin of the haskap subspecies which is native to the Japanese island of Hokkaido, which was once called Yez or Yezo Island. Yezberry Maxi yields a good crop of exceptionally large fruit and needs to be planted with another Yezberry selection for cross-pollination and fruit set. Yezberry Solo is self-pollinating but will set more fruit with a pollinator.

Advice for growers

Growers can bring in liners or small pots of Yezberry haskaps in June and have them ready to sell finished in 1-gallon pots the following spring. It is a fast growing crop, given the nature of honeysuckle, and edibles are in high demand from retailers and consumers who are looking to grow their own food. Berries are typically produced one to two years after planting. Mature plants can produce as much as 13-15 pounds of fruit per season.

Unlike blueberries, haskaps are much less fussy about soil pH, not requiring acidic soil to thrive. Very young liners are best planted a bit deep and long shoots on dormant plants can be trimmed back to 2-3 inches at planting. Maintain evenly moist, but not wet, soil and in the ground, mulch plants well. In the warmest end of their hardiness zone, botrytis can be a problem, but typically these plants are free of any major pests or diseases. The biggest pest is birds, especially cedar waxwings, which can devour every berry on the bush in a very short time. Use ½-inch netting raised up above the plants to keep birds away.

Thompson is now retired, but continues to feed her passion doing the work she loves, developing suitable cultivars of haskaps for the Pacific Northwest, funded by small research grants. Undoubtedly, she has long left her mark on the world of horticulture in over six decades of work around the world. Her unmatched knowledge and passion will live on through the countless people she has mentored, her extensive and detailed research on fruit and nut crops, her contributions to the U.S. National Plant Germplasm System, and her prized Yezberry haskap introductions through Spring Meadow Nursery. She is truly a one-of-a-kind horticulturist.

Susan Martin specializes in horticultural marketing, content generation and management, working with green industry clients in trade and consumer sectors. She can be reached at gardenersuesnews@gmail.com.