Can You Grow Boysenberries in Northern Idaho?

Hardiness

• Most of northern Idaho falls in U.S. Department of Agriculture plant hardiness zones 6a and 6b, a climate suitable for growing boysenberries, which thrive in USDA zones 5 through 10. A few areas north of Sandpoint fall in USDA zones 5a and 5b. These areas are marginal for growing boysenberries. Exceptionally cold winters might damage or kill the plants.

Growth

• Boysenberries are a type of trailing blackberry with a growth pattern similar to raspberries. The plants produce fruit on floricanes, which are the canes that began growing the previous summer. In severe cold, these canes can be damaged or killed, destroying the harvest for the coming summer. Late frosts can also damage the flowers.

Planting and Care

• Of all the trailing blackberries, boysenberries -- along with marionberries -- are the least cold hardy. They grow best when planted in well-draining, rich soil in an area that gets at least six to eight hours of sunlight in the summer. In marginal areas, a layer of wood chip mulch or straw on the soil can help regulate soil temperatures and keep them warmer. You can also try bending the tips down to the ground and covering them with soil for additional protection.

Alternatives

• Boysenberries will grow in most parts of northern Idaho, but pay attention to the microclimates within your own yard. If your property is at a higher altitude or is in a windy, exposed location, boysenberries might not be the best choice. Try blackberries adapted to cool climates, such as "Chester" (Rubus "Chester"), which is hardy to USDA zone 4 instead. Another option, raspberries (Rubus spp.) are more cold hardy than blackberries, thriving in USDA zones 2 through 7.