April 22, 2010 at 8:43 a.m.
The average gardener, (this includes me) doesn't give enough attention to raising crops, including raspberries. They need full sun and the type of soil is extremely important for starting them. About 90 percent of the root system is in the top 20 inches of soil where the root must take up moisture and nutrients. Raspberry plants will not tolerate poorly drained soil. Even temporary water-saturated soil conditions can cause serious injury. This includes poor cane growth and increased incidents of soil-borne diseases and plant death.
There are two types of raspberries for our area, (zone 3) summer bearing and everbearing. Summer bearing are raspberries that will bear once a year, usually the beginning of July. Boyne is the summer variety Master Gardeners offer. It is a mid-season berry developed in northern Minnesota, so it is extra hardy. Boyne yields very well and has a dark red fruit.
Two different ever-bearing varieties are available which means that once they starts bearing, it usually will bear until a killing frost. The most popular ever-bearing variety throughout the country is Autumn Britten. (We are sold out of this variety for this year.) It ripens about the fifteenth of August and will yield well into the fall although the yield is less in late fall. It has a very large, firm berry that is very flavorful. It also has shown to be very winter hardy. We have offered Heritage as long as we have been selling plants. The fruit is medium sized, red, and very firm. The canes are tall, vigorous, and very erect and sturdy requiring no support. The only drawback is they won't be in full harvest until about the fifteenth of September. If we have an early frost you may lose the main production season. Since I sell most of my crop, I am willing to take the chance because they are so sweet with a long shelf life.
The pruning of summer and ever-bearing is quite different. Summer bearing raspberries like Boyne need to be pruned in the spring. Cut out the old dead canes that produced last summer. I don't cut back the new canes any lower than four feet or you will get a lot of bush, but no berries. Besides, 70 percent of the yield is in the top third of the cane. If they are going to bend over or are too tall, prune accordingly.
One of the reasons I like ever-bearing raspberries like Autumn Britten and Heritage is that I prune them back to two or three inches from the ground after harvest and after the ground has frozen hard. The reason for this is because if the ground is not hard you may disturb the roots, thus the fear of winterkill. Some like to treat ever-bearing like summer bearing as they will get an earlier crop. I found that the berries were not as large or as sweet the time I didn't cut them down, but that's me.
Although we are out of Autumn Britten raspberries and Sparkle strawberries, we still have a large variety of plants. Contact the Extension Office at 651-213-8901 for more information on plant orders and our Spring Class Series.