Great Plains Gardening
April 18, 2003
This week, as promised, we shall look at raspberries for the home garden. The information I have comes from CSU fact sheet #7.001, available at the extension office. I have had some experience with raspberries. Unfortunately the variety I had was the summer bearing, which is not generally recommended for our area. Most of my bushes died out from the very severe dry conditions the fall and winter of 2001-2002. If I decide to try again, I shall follow the advice of my Master Gardener instructor and try a fall bearing variety.
"Selected varieties of red and yellow raspberries may be successfully grown in Colorado at elevations up to 8,000 ft. Colorado’s climate is not especially favorable for bramble fruit production, and only red and yellow raspberries (Rubus idaeus) are recommended. Black and purple raspberries, as well as blackberries, boysenberries, loganberries and dewberries, require special winter protection and are not recommended for Colorado".
"There are two types of red raspberries: summer-bearing and fall-bearing. The standard varieties are biennial summer-bearers that produce canes the first season and bear fruit on short lateral branches of these canes the following summer. Fall-bearing raspberries also produce canes (suckers) from the roots but require no dormant period for fruiting. These canes bear fruit in August and September of the first season. These canes may over winter and produce a light summer crop, but this is at the expense of a reduced fall crop."
"Based on Colorado State University tests, fall-bearing types, particularly Heritage and Redwing, seem best adapted to the Front Range area."
"Red raspberries grow in most garden soils if they have ample organic matter and adequate drainage. For summer-bearing raspberries in good garden soil, apply only a maintenance amount of fertilizer: 4 pounds of ammonium sulfate and 2 pounds of treble super phosphate per 1,000 square feet. However, if the soil has not produced a good garden, have it tested before planting. If soil is not tested, apply 8 pounds of ammonium sulphate, and 4 pounds of treble super phosphate, 2 pounds of zinc sulfate, 2 pounds of iron chelate and 10 bushels of organic matter per 1,000 square feet. Work these in before planting. For fall-bearers, increase the amounts of fertilizer by 50%."
"Maintain soil fertility with a spring application of 4 pounds of ammonium sulfate and 2 pounds of treble super phosphate per 1,000 square feet. Scatter among the canes and cultivate into the soil."
"Apply enough water to maintain a moderate moisture level in the root zone. Withhold water after the first frost to help harden off the plants. A late November watering reduces winter drying."
"Red raspberries are commercially propagated by rooted suckers. Plant them in the spring, 2 to3 feet apart in rows 5 to 10 feet apart, depending on the width of the cultivating equipment. After planting, cut the tops to within 4 to 6 inches of the ground. Be careful planting bare-rooted stock because it is somewhat difficult to establish. Soak bare-root plants in a bucket of water five hours to overnight to help them get established."
"After one or two years, suckers fill in the row to form a hedge of canes. Thin the suckers to 6 inches. The hedge row should not be more that 2 feet wide at ground level."
"Fall bearing raspberries seldom require trellising; however, summer bearing varieties may require some kind of support. Stretch a wire on either side of the hedgerow, 3 feet above the ground. This wire confines the canes to the hedgerow. To make them stand erect you may have to tie the canes to the wire with soft twine."
"Remove the canes of summer bearing varieties by cutting them off at the ground after they bear fruit. Dispose of these canes-they often harbor insects and disease. In the spring, remove the dead, weak and small canes, leaving canes at least 6 inches apart in the hedgerow. Remove winterkilled tips of the remaining canes. Mow the canes of fall bearing varieties to ground level after the fall harvest."
"To obtain a crop of summer bearing raspberries in most areas of Colorado protect the canes during the winter. Sometime after November 1, lay the canes down in one direction and hold them in place with a shovelful of soil on the tips. Plow or shovel a shallow furrow along each row and roll the soil over the canes. In early April, use a pitchfork to lift the canes out of the soil. Put the soil used to cover the canes back into the furrow."
"The advantage of fall bearing varieties is that winter covering is not needed-the canes are mowed off after harvest. However, if a summer crop is desired from these canes, they must be protected as described for summer bearing raspberries."
"By the third year, a 25-foot hedgerow of red raspberries should yield 15 to 20 pounds of fruit per year under optimum conditions. After this, productivity will decline. After eight to ten years, relocate the bed, starting with new stock."
"Raspberries are affected by a wide range of diseases and insects, as are most cultivated plants. You can avoid most of these problems for several years by purchasing only quality, true to name, disease free raspberry varieties. It is almost inevitable, however, that during hot, dry weather, raspberries along the Front Range will be infested with spider mites. The mites themselves are not obvious, but their presence is indicated by tiny; yellow spots on the leaves, which eventually turn brown. Spray the mites, which feed on the underside of the leaves, with one tablespoon of diazinon 50% wettable powder or 1 teaspoon malathion 57% emulsifiable concentrate per gallon of water. Observe the required waiting period between spraying and harvesting, as stated on the label."
Until next time…