By Marrilee Johnson
Boysenberries are a delicious, low-sugar treat, appreciated by pie and jam connoisseurs alike. The Boysen berry is classified as a blackberry along with the Olallie berry and the Marion berry. However, part of it is a deep rich purple similar to a blackberry, while other parts of it are as red as a raspberry. Its aroma and sweet-tart flavor are suggestive of a raspberry, but its larger size resembles the blackberry. All in all, it is distinctive in its own right, and may well be the ultimate berry for making jams and pies.
The boysenberry was discovered in California. A botanist named Rudolf Boysen discovered a “chance seedling” and decided to give it a try. In 1920 George Darrow of the USDA heard about a large berry that had been propagated in California and contacted Walter Knott who was known for his knowledge about growing berries. Boysen had lived next to Knott but had long since moved away. Knott retrieved some of the berry bushes from Boysen's farm and began to propagate them. He named the berry after Boysen, and sold them at his berry stand—the beginning of Knotts Berry Farm. At one point, there were 2400 acres commercially producing boysenberries. But they proved difficult to sell because their thin skin allowed the juice to leak, causing rapid decay. Large-scale production accordingly dwindled. The delicate nature of these berries provides a good reason to learn how to grow them oneself.
With good preparation and proper care, boysenberries can be grown in the Chico area. This plant needs porous, fast-draining soil with pH between 6.0 and 7.5. Planting is mostly done during bare root season (December-February). Canes should be planted in a space three to four feet wide, and spaced three and one-half to four feet apart. Add compost and dig a hole about one foot deep to loosen the soil for planting. After planting, irrigate and cover the soil with mulch.
Boysenberries do not require much fertilizer. A good time to provide an extra “boost” is in the spring when the new growth begins to leaf out, and again when bloom begins. An organic fertilizer such as bone meal or fish meal can be applied. Berries require moist soil but do not thrive with “wet feet.” A drip line or soaker hose is the most efficient method of watering, since water on the fruit or leaves can trigger disease. Attention to watering is critical from bud formation through berry development and harvest.
Boysenberries are best trained on a wire trellis, placing wires at two, four, and six feet. As the berry canes grow, gently weave the canes between the wires and upward. Boysenberries can have thorns or be thornless. Planting the thornless variety will make training the canes and picking the berries much easier.
When berries are large and more black than red, they are ripe and ready to be picked. They have a very short fruit production season and one must be prepared to pick the ripe fruit every other day. Be sure to set aside time for making jams and pies or preserving the berries by canning or freezing them.
Once the growing season is complete and the berries have been harvested, prune out the old canes and train the new canes on the trellis. This attention is vital for control of a boysenberry plant. Neglect will produce new berry plant shoots emerging in parts of the garden not meant for berry growing. Containment of these plants is important!
Want to learn more? Attend the workshop on Growing Berries and Grapes (Wednesday, April 2), part of the Master Gardeners' Spring Workshop Series. For more information about the series, which runs through early June, and to register for the upcoming workshops, visit our website. All workshops are free, but registration is required.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.