Growing Raspberries in Colorado Gardens
- Types and cultivars
- Planting raspberries
- Fall-bearing primocane-fruiting) cultivars
- Summer-bearing floricane-fruiting) cultivars
- Common raspberry pests
Fall- bearing (primocane-fruiting) red raspberry cultivars are typically more hardy than summer crop cultivars. Suggested cultivars include Autumn Britten, Polana, Jaclyn, Caroline, and Heritage. Joan-J and Himbo-Top have not performed well in Colorado trials.
Summer-bearing (floricane-fruiting) red raspberry cultivars have some winter hardiness problems in climates like Colorado, with frequent winter to spring and back to winter temperature swings. Suggested cultivars include Nova, Boyne, and Killarney.
Black raspberry or “blackcap” – Suggested cultivars include MacBlack and Jewel.
Purple raspberries are a hybrid of red and black. Suggested cultivars include Royalty.
Yellow raspberries are a mutation of red. Suggested cultivars include Anne.
Figure 1. Raspberries make a great crop for the home gardener.
With good growing conditions, a raspberry patch may last 10 to 15 years. Viral diseases and hardiness problems frequently shorten the life of a patch. Raspberries need full sun, but avoid reflected heat in areas with hot summer temperatures. In open windy areas, wind protection is important as dry winds can dehydrate and kill exposed canes.
Raspberries prefer a deep, well-drained, sandy loam soil. They perform poorly on compacted clayey soils and soils with poor drainage. On clayey soils, plant in a raised bed. Because raspberries are a long-term crop, extra efforts to improve the organic content of the soil to 5% gives good dividends.
Due to soil borne diseases, do not plant raspberries where raspberries, strawberries, tomatoes, peppers, eggplant, potatoes, or vine crops (cucumbers, squash and melons) have been grown in the past four years. To reduce virus potential, do not plant raspberries next to blackberries. To help manage virus problems, purchase certified virus-free nursery stock.
In the home garden, raspberries are generally planted in a hedgerow. Place plants in a row 12 to 18 inches between plants with four to eight feet between rows (depending on trellising system and equipment used). If planting bare-root plants, soak plants in water for a few hours before planting. Dig shallow holes large enough to spread out the root mass and set plant with the top root one to two inches below soil level. Water plants to settle the soil. Cut newly planted canes to 6 inches. Care of the new planting should be similar to vegetable transplants with frequent, light irrigation until the plants become established.
Allow canes to fill in making the hedgerow. By hoeing or cultivation, routinely remove any canes that come up outside of the hedgerow. For higher yields and reduced pest problems, keep the hedgerow width to only 8 to 12 inches for fall cultivars and 12-18 inches for summer cultivars. [Figure 2]
Figure 2. Red raspberries in a hedgerow. For higher yield, keeps width of hedgerow to only 8 to 12 inches wide for fall bearing cultivars.
Primocane vs. Floricane – The crown and roots system of raspberries are perennial. The canes are biennial. Primocane refers to the first year canes; floricane refers to the second year canes.
In fall-bearing cultivars, the fall crop starts at the top of the primocane (new cane this summer), working its way down the cane with each picking. Next summer, the crop starts at the point where the fall crop ended the previous season, continuing downward.
For best yields and high fruit quality, prune to a fall crop only. In February/March, prune all canes to the ground. This eliminates the summer crop, putting all the growth into the superior fall crop. This also helps eliminate winter injury problems and many common insect pests.
For a fall and summer crops, prune the same as summer-bearing cultivars.
1. Primocanes (new canes the first year) are not pruned.
2. In spring (February/March), prune as follows:
- Remove spindly canes, leaving stocky canes ¼ inch in diameter and larger. Thin stocky canes to about 10 canes per foot of hedgerow.
- For larger fruit size, tip canes at a convenient height where they will be self-supporting, typically around five feet. Canes may be tied in clusters to a trellis.
- For larger yields, do not top canes. Canes may be tied in clusters to a trellis
3. Mid-summer when the fruiting is finished, remove all floricanes (flowering/fruiting canes) to the ground. They will not fruit again. This makes room for the new crop of primocanes.
Raspberries are considered easier to manage if trellised. Examples of trellising systems are given in figures 3-5. [Figures 3-5]
Figure 3. The one-line trellis system has wires running at 30 inches and 4½ to 5 feet. Canes are tied to the lines in bundles.
Figure 4. The two-line trellis system added an 18-inch cross arm at 4 ½ to 5 feet. Wires are run at the edge of the cross-arm forming a box. Canes are tied in bundles on the two lines.
Figure 5. The T-trellis system is popular for fall bearing (primocane-fruiting) cultivars. At knee height, a cross arm and wire form a box. Canes are free floating inside the box.
Raspberries need about 1 inch of water (rain and irrigation) per week during blooming/fruiting. Depending on soil type, this may require irrigation once to twice a week. When watering, avoid wetting the leaves and fruit as this can lead to disease problems. Raspberries work great with drip irrigation under wood chip mulch.
Water use is significantly less during non-fruiting times. Iron chlorosis (yellowing of leaves with veins remaining green) is a common symptom of over-watering. [Figure 6]
Figure 6. Iron chlorosis (yellowing of leaves with veins remaining green) is a common symptom of over-watering. Raspberries are commonly over watered in the spring.
A good guide for fertilization is to observe plant growth. Leaves should be healthy green and primocane should grow to five to eight feet. Adjust actual fertilizer rate if plants grow too tall or are too short.
Fertilizer all raspberries in the spring as growth starts and repeated in early June. For fall bearing cultivars, make a third application in August. Apply ½ to 1 cup of ammonium sulfate (21-0-0) or similar fertilizer per 10 feet of hedgerow. The fertilizer may be broadcast over the hedgerow area and watered in or placed in a band a foot to the side of the row.
If using compost or manure, make application in the late fall or early winter, but avoid early fall application which can push late fall growth.
- Winter dehydration is less of a problem in fall bearing cultivars where they are pruned to the ground each spring.
- >Sunburn of fruit (light color patches on the top side of fruit) is common in hot weather. Raspberries prefer cooler temperatures.
- Iron chlorosis (yellow leaves with veins remaining green) is a common symptom of springtime over-watering. Correct watering problems. For additional information on iron chlorosis, refer to CMG GardenNotes #223, Iron Chlorosis.
Insects and mites
- Grasshoppers love raspberries!
- Spider mite populations explode in hot summers and following the use of the insecticide Sevin (carbaryl). Leaves are bronzed by these tiny insect-relatives. For additional details, refer to CSU Extension Fact sheet #5.507, Spider Mites.
- Cane borer, crown borer, and stem borer are common borers of the canes. These are less of a problem in fall- bearing cultivars where the canes are removed to the ground each spring. For additional information, refer to PlantTalk Colorado #1478, Raspberry Cane Borers
- Plant bugs cause misshapen fruit.
- Raspberry sawflies are caterpillar-like insects that feed on leaves.
- Leaf rollers
- Spottedwing drosophila flies can affect ripe raspberries, in particular fall bearing cultivars.
- Virus complex – Raspberries are rather prone to variety of viruses. Simply remove the patch when the fruit becomes small and the patch is less productive. Start the new patch in another area of the garden using new, virus-free plants.
CMG GardensNotes on growing fruit
- Growing Blackberries in Colorado Gardens, #762
- Growing Raspberries in Colorado Gardens, #761
- Growing Grapes in Colorado Gardens, #764
- Growing Strawberries in Colorado Gardens, #763
- Growing Tree Fruits in Colorado Gardens, #771
- Reference and Review Questions:Small Fruits, #760
- Reference and Review Questions: Tree Fruits, #770
- CMG GardenNotes are available online at www.cmg.colostate.edu
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- Copyright. 2014. Colorado Master Gardener Program, Colorado State University Extension. All Rights Reserved. CMG GardenNotes may be reproduced without change or additions, for nonprofit educational use.
Revised October 2014