Raspberries for the Home Garden

Fact Sheet 7.001 Gardening Series | Fruits & Vegetables

By J. Reich, H. Hughes and J.E. Ells* (4/20) Quick Facts

Selected varieties of red and bearing raspberries flower and fruit Of all bramble fruits, yellow raspberries (Rubus idaeus) along the upper portions of canes only red and yellow may be successfully grown in that are in their first year of growth. rasp-berries are recommended for Colorado. Native raspberries can These canes may overwinter and general cultivation in grow to 10,000’ elevation. Colo- produce a light summer crop on Colorado. There are rado’s climate is not especially their lower portions, followed by a now a few hardy favorable for bramble fruit produc- second crop on the tips of the varieties of black tion, and only red and yellow current season’s growth in the raspberries. raspberries are recommended for fall (up until freezing temperatures). Blackberries are con- sidered marginal, due to cultivation statewide. Several inadequate hardiness, varieties of blackberries can be Varieties but some varieties can grown in the lower-elevation areas be successful. of the state. New hardy varieties of Based on Colorado State University Red raspberries grow black raspberries including Niwot tests, with a few exceptions, fall- well in most garden soils that are amply and Pequot can work in some bearing types seem best adapted areas of Colorado. Purple supplied with organic to the Front Range. Both fall- matter and adequately raspberries (see variety table), bearing and summer-bearing drained. boysenberries, loganberries and varieties do well on the Western Bramble plants are dewberries require special winter Slope. Hardy varieties with mid- perennials, but their protection and are not recom- season production should be canes are either annual mended for Colorado. chosen for short-season, high or biennial structures. Plant only true-to-name, elevation areas. Growing a variety disease-free stock from Types of types may ensure a better crop. reputable sources. (See the variety chart for recom- Twenty-five feet of row There are two growth-types of mended varieties for Colorado). should produce 15 to 20 raspberries: “summer-bearing” pounds of raspberries per year. (floricane or “June bearing”) and Soil Preparation fall-bearing (Primocane or ever- *J. Reich, Colorado State University bearing”). Summer- bearing Red raspberries grow in most Extension horticulture agent, Boulder County; H. Hughes, Colorado State varieties produce flowers and fruit garden soils if they have ample University professor, and J.E. Ells, once per season on second-year organic matter and adequate Colorado State University Extension vegetable crop specialist and asso- canes. This means that a given drainage. For summer-bearing ciate professor (retired), horticulture cane will grow vegetatively in its and landscape architecture. 8/2011 raspberries in good garden soil, Updated by Yvette Henson and Susan first year, followed by fruiting on apply only a maintenance amount Carter, CSU Extension Agents, 4/20 that cane in its second year. Fall- of fertilizer of a nitrogen fertilizer in

extension.colostate.edu 1 © Colorado State University Extension. 11/12. Revised 4/20. Raspberry Variety Chart for Recommended Varieties for Colorado

2 spring. Some areas in CO may require phos- as “handles.” A handle consists of a 12-18 phate fertilizer. A soil test is recommended to inch section of a dormant cane with a large determine what other nutrients are needed. root mass attached. Soak bare-root plants in Use cane growth to determine if there has a bucket of water 1 hour to help them get been enough N applied. The space between prepared for planting. Plant them in the the buds (internode) optimally is 4”. Less you spring, 2 to 3 feet apart in rows 5 to 10 feet need N, greater the plant is too vigorous so apart, depending on the varieties growth reduce or skip adding nitrogen. Soils over 7 characteristics, how much pathway space pH may be low in zinc, iron and manganese. In you desire and the width of any cultivating general, fall bearing raspberries require 1.5-2 equipment that may be used. After planting, times more nitrogen then summer bearing. cut the tops to within 4 to 6 inches of the The chart refers to good soil, new bed or ground. untested refers to the amount of organic matter. Soils with higher organic matter 5%, After one or two years, suckers fill in the row need little to no fertilizer. Test every 3 years. to form a hedge of canes. During dormant- An application of organic matter will help to season pruning, thin the resulting collection conserve water and reduces N need. of canes so that you leave five to six of the strongest canes per linear foot. The hedge- Apply enough water to maintain a moderate row should not be more than 2 feet wide at moisture level in the root zone. During ground level. An application of organic flowering and fruiting, more water is required. mulch will conserve water and decrease Withhold water after the first frost to help weed competition. harden off the plants. A late November watering reduces winter drying. Trellising Trellising is advisable for all bramble crops in Planting Raspberries Colorado. Without some type of support, Red and yellow raspberries are commercially canes will flop and sprawl in such a way as to propagated by rooted suckers. These can make weed control and harvesting much easily be purchased from a variety of online more difficult (and prickly). Stretch a wire on and mail-order sources. They are typically sold

Figure 1: Raspberry trellis with dormant canes secured to wires.

3 either side of the hedge row, 3 feet above the prune fall-bearing varities. The first, and ground depending on the variety and trellis easiest method is to mow or cut all the canes to structure. These wires confine the canes to the ground level after the fall harvest and before hedge row. To make them stand erect, you may spring growth. New canes will be produced in have to tie the canes to the wire with soft twine. the spring. This eliminates the summer crop See Figure 1. For larger fruit size, tip canes at a but also eliminates hardiness problems and convenient height. For larger yield, do not tip cane borers and gives a larger harvest overall, canes. unless an early frost occurs. The second is to remove the parts of the canes that fruited the Pruning previous year, which leaves the bottom portion For of summer- bearing varieties, remove of the cane to produce the following summer. the spent floricanes by cutting them off at the New canes that grow from the crowns that ground after they bear fruit. Dispose of these spring will produce a fall crop at the tips. This canes – they often harbor insects and disease. method allows for two harvests, giving at least In the spring, remove the dead, weak and small one harvest in short season areas. The canes. Remove winter- killed tips of the re- disadvantage is that it will result in a reduced maining canes. There are two methods to fall crop.

4 Winter Protection Yield To obtain a crop of summer-bearing By the third year, a 25-foot hedge row of red raspberries in many areas of Colorado, it will raspberries should yield 15 to 20 pounds of fruit be necessary to protect the canes per year under optimum conditions. After this, it during the winter. This does not appear to be is likely that productivity will decline gradually. necessary for the varieties ‘Nova’ and ‘Boyne,’ After eight to 10 years, relocate the bed at least as they appear to have adequate winter 50-75’ away, where no brambles or solaneous hardiness in all but the coldest locations. For plants have been in four years. Start with new all other summer-bearing varieties, follow certified disease free stock. these steps: After November 1, lay the canes down in one direction and hold them in place Disease and Insects with a shovelful of soil on their tips or apply Raspberries can be affected by a wide range of mulch. Plow or shovel a shallow furrow along diseases and insects, as are most cultivated each row and roll the soil over the canes. In plants. You can avoid most of these problems early April, use a pitchfork to lift the canes out for several years by purchasing only quality, of the soil. Put the soil used to cover the true-to-name, disease-free raspberry varieties. canes back into the furrow. This typically means mail-ordering bare-root plants. These should be planted mid-April The advantage of fall-bearing varieties is that through early May. winter covering is not needed -- the canes are mowed off after harvest. It is not uncommon, during hot, dry weather, for However, if a summer crop is desired from raspberries along the Front Range to be these canes, they must be protected as infested with spider mites. The mites them- described for summer-bearing rasp-berries. selves are not always obvious, but their In areas with a lack of snow cover, mulch can presence is indicated by tiny yellow spots on help prevent desiccation and insulate the the leaves, which eventually turn bronze and/or plants. brown. The most effective way to avoid mite

5 problems is to maintain healthy plants. This Spotted wing drosophila is a newer insect means applying a balanced fertilizer at least coming to Colorado around 2013. It is once a year, in May. Many plantings will different from other fruit flies in that its benefit from additional fertilizer in June and ovipositor is like a saw so it can penetrate July. In addition, make sure plants are good fruit and lay eggs. Refrigerate fresh adequately watered. Drought-stressed picked berries, clean up dropped fruit and raspberry plants are a great place for spider trap and monitor to control. mites to feed and breed. It is also important to prevent the planting from becoming too References dense, as an overcrowded planting makes Lawrence, F. T. Growing Raspberries. life easy for mites. This can be achieved Farmer’s Bulletin 2165, U.S. Government most effectively by removing the thinnest, Printing Office, Washington , D.C. 20402. weakest canes, thereby allowing more light 1979. and air to reach the center of the planting. Regularly watering the foliage during hot Shoemaker, T.S. Small Fruit Culture, 5th weather will also help control mite Edition. AVI Pub. Co. Inc. Westport, Conn. populations. 1977.

Insecticides tend to be ineffective against Bushway, L., Pritts, M.P. and Handley, mites, and their use often makes mite D.T. (eds.) Raspberry and Blackberry problems worse by killing a variety of Production Guide for the Northeast, Midwest beneficial, predatory arthropods. If a spray and Eastern Canada. NRAES-35. Ithaca, New is desired, best results are often achieved York. 2008. with a “summer weight” (2%) application of horticultural oil. Britney Hunter, Rick Heflebower, Shawn Olsen, Brent Black, Diane Alston and Thor Raspberry cane borers can be an important Lindstrom. A Comparison of 16 Summer- pest in Colorado. Symptoms of this pest Bearing Raspberry Cultivars for Northern include a sudden wilting and drooping of Utah, Utah State University Extension, the tops of canes. The white larvae of the January 2015. borer, if left uncontrolled, burrow down- wards through the center of the cane and kill it.

Management in the garden is best achieved by removing the affected canes at the first sign of damage. Depending on location, mid-May through June is when these pests tend to do their damage. If caught early enough, while the larvae is still near the tip Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. CSU Extension programs are of the cane, the undamaged portion of the available to all without discrimination. No endorsement of cane may be saved, allowing it to produce products mentioned is intended nor is criticism implied of fruit. products not mentioned.