Growing Raspberries in the Home Garden
WHY GROW RASPBERRIES?
The next best thing to growing your own vegetables is growing your own fruit. Small fruits are generally easier for the home gardener to manage than orchard fruits. Berries, such as raspberries, are popular choices and very rewarding to grow. Unfortunately, the soft fruit is highly perishable and has a short shelf life in stores. That’s why it’s best to grow your own.
The delicious sweet-tart flavor of fresh raspberries is reason enough to grow them. But if you need further convincing, then consider their health benefits. Raspberries are rich in vitamins and minerals, antioxidants, and fiber. One cup of this tasty fruit provides more than 50% of the minimum daily target for vitamin C, 8 grams of dietary fiber, and only 5 grams of sugar. And that’s not all. For a more complete listing of the nutritional and health benefits of berries, check out Oregon State University Extension Service’s Berry Health Benefits fact sheets.
WHEN IS A BERRY NOT A BERRY?
Despite the name, raspberries are not actually berries. Blackberries and strawberries aren’t either for that matter. In botanical terms, a true berry is a multi-seeded fleshy fruit that develops from a single flower with a single ovary. By that definition, true berries include blueberries, cranberries, elderberries, gooseberries, and lingonberries. Raspberries develop from flowers that have more than one ovary. A raspberry is essentially an aggregate fruit made up of multiple parts clustered around a core. Each little bead-like part, called a drupelet, develops from a single ovary and contains a single seed.
So now that you know what a raspberry isn’t, let’s talk about what it is. Raspberries belong to the Rubus genus, which includes blackberries, boysenberries, loganberries, and tayberries. Members of this genus are called bramble fruits because of the prickles on their stems. Except for some hybrids that have been bred to be thornless, most raspberry varieties are thorny. Raspberry plants are also referred to as caneberries or cane fruits because the berries form on long thin woody canes.
The root systems of raspberry plants are perennial and can live for about 5 to 12 years before they need to be replaced. The shrub-like plants produce a thicket of green vegetative canes that are biennial and live for only two summers. In their first year, the green canes are referred to as primocanes. In their second year, the canes, now mature and browner in color, are referred to as floricanes. Floricanes leaf out in spring, produce flowers, and set fruit. Once they finish fruiting, the canes die. For pruning purposes, it’s important to know the difference between a primocane and a floricane. But more on that later.
CHOOSING WHICH RASPBERRIES TO GROW
Raspberries fall into three broad categories identified by color: red, black, and purple. Of the three, red raspberries are generally more successful in warmer areas of Virginia, whereas all raspberry types may be successfully grown in cooler mountain regions of the state.
RED (Rubus idaeus). Red raspberries are native to most of the temperate regions of earth including North America. Red-fruited raspberries sucker from their roots and spread. Most of the fruit is concentrated in the top one third of shoots, which benefit from being trellised. Red varieties fall into two basic types: summer-bearing and everbearing (sometimes called fall bearing).
- Summer-bearing varieties bear one crop of fruit. Members of this type follow the traditional biennial life cycle of a bramble fruit: They send up green shoots (primocanes) their first year and bear fruit the following year on floricanes in mid-summer. The canes die after fruiting.
- Everbearing varieties bear two crops of fruit and are often referred to as primocane varieties. That’s because they bear fruit on the mature tips of first-year growth in late summer through fall. They can also produce a small crop in summer on the second-year canes, just below the area where they produced fruit the previous fall.
Some suggested red raspberries to grow include:
- Heritage — Resistant to most diseases but susceptible to late leaf rust. The thorny canes are very vigorous, erect, and sturdy.
- Himbo Top – Has an upright form and a high tolerance to Phytopthora root rot disease.
- Joan J – Has thornless canes that are vigorous and upright.
- Josephine – A vigorous, upright selection that needs little, if any, support. Resistant to leaf hopper and Phytophthora root rot.
- Caroline — Has vigorous canes with short fruiting laterals and moderate to good resistance to Phytopthora root rot.
Yellow or gold-color raspberries belong to the red raspberry category, are similar in growth habit, and should be treated the same as any other red raspberry. The yellow or gold fruit color is a mutation, which prevents production of the pigment normally found in red raspberries.
Suggested yellow or gold-color varieties include the following, which are both everbearing varieties:
- Anne – Largest and best-tasting of the yellow varieties.
- Fall Gold — A more compact variety with upright, thorny canes topping out at about 24” to 36”.
BLACK (Rubus occidentalis). Black raspberries are native to North America but have only been domesticated since the mid-1800s. By the way, don’t confuse black raspberries with blackberries. They are two separate species belonging to the Rubus genus. To tell the plants apart, black raspberry canes grow more upright whereas blackberry canes grow long and arching. When harvesting the fruit, the core of each raspberry remains attached to the stem, leaving the berry with a hollow middle. The blackberry core detaches from the stem along with the berry and is part of the edible fruit.
Black raspberry varieties bear fruit a little earlier than the red varieties but tend to be more susceptible to viral diseases than the red varieties. They grow new canes from the crown rather than from root suckers. The tips of black raspberry canes need to be pruned to encourage branching and thus more berries.
Examples of black raspberries include:
- Cumberland – A long-favored vigorous, productive floricane-bearing variety.
- Jewel — A high-yielding, floricane-bearing selection. Plants have a weeping form and are cold hardy, vigorous, and resistant to most diseases.
- New Logan — A heavy-yielding selection that withstands drought conditions well.
PURPLE (Hybrids). The members of this category were recognized as hybrids of red and black raspberry species as early as 1870. Their berries are not as sweet as those of their two parent species and are best used for processing into jams and jellies. Like their black raspberry parent, they produce their canes predominantly from the crown. However, like their red raspberry parent, they may form suckers from their roots. Members of this category should be grown in the same manner as black raspberries.
Examples of purple raspberries include:
- Brandywine — Considered one of the best of the purple raspberry selections. It produces tart, reddish-purple fruit on tall, thorny canes.
- Royalty — The most widely planted purple variety. The soft, sweet flavored fruit is borne on productive upright, thorny canes and enjoyed fresh as well as processed.
ESTABLISHING RASPBERRY PLANTS IN THE HOME GARDEN
Plant raspberries in late fall or early spring in deep, well-drained soil that is rich in organic matter. Before planting raspberries, have the soil tested about 4 to 6 months in advance. This will allow plenty of time to amend the soil based on soil test results. The Virginia Cooperative Extension (VCE) recommends a pH of 6.0 to 6.5. If the pH is too low, it should be raised to the level suggested by the soil test with dolomitic lime.
Space the plants 3 feet apart for red raspberries and 4 feet apart for black or purple raspberries in rows 8’ to 10’ apart. Prepare planting holes that are large enough to allow the roots to spread out naturally. Position the crown of the plant (where the stem and root come together) one inch below ground level.
Tamp the soil firmly around each plant to remove air pockets from the roots.
Water each new plant well immediately after planting. Water is also critical to raspberries when they are blooming and when the berries are developing. However, avoid overly saturating the soil. Waterlogged soil can increase susceptibility to root rot and other diseases. If the soil does not drain well, consider planting raspberries in raised beds. For best results, use drip irrigation to confine water to the root area.
Use an organic mulch to cover the soil. That will keep the soil moist and cool as well as reduce soil crusting and help control weeds.
Apply fertilizer only as the results of a soil test indicate. Too much fertilizer can cause excess vegetative growth and a decrease in fruit quality. If fertilizer is needed, apply about 0.5 pound of nitrate of soda or 0.75 pound of 10-10-10 per 100 square feet.
It’s important to remove old second-year canes to make room for new first-year canes. This helps prevent disease and promote plant vigor. To tell the difference between old and new canes, older ones are grayish brown in color and have rough-looking, peeling bark. New canes are smooth and green.
Prune dead canes of both summer fruit-bearing and everbearing red raspberry plants in late winter or early spring before new growth emerges. Also prune any small, spindly, or damaged canes. Continue to thin out canes leaving only the thickest, healthiest ones. When you finish, you should have only three to five canes per linear foot. The recommended row width is 1-1/2 to 2 feet. If you want to confine your plants to that width, prune out any new canes that you see growing outside those boundaries.
When pruning everbearing raspberry plants, some gardeners prefer to mow or cut down ALL the canes before new growth emerges. While this makes the pruning task a lot simpler, it does sacrifice the mid-summer crop. This may not be too big a sacrifice since the summer crop is usually small and the larger crop occurs in late summer through fall on these varieties.
The canes of black and purple raspberry plants tend to grow longer than those of the red varieties. As black raspberry canes arch over, they can form new roots where their tips touch the ground, resulting in overcrowding. To prevent this from happening, snip off the top 2 or 3 inches of stem growth in summer when the new canes are about 30” long. This will solve the rooting problem, keep the canes at a more manageable height, and encourage the development of more lateral shoots and fruit buds. Cut dead two-year canes back to the ground in late winter or early spring.
Everbearing raspberry varieties tend to be more erect than summer-bearing varieties and rarely need to be trained to a trellis. Summer-bearing varieties may need support as fruit production weighs down the canes. One common method is to install sturdy wood or metal posts with supporting crossbars at either end of the row. Stretch wire between the crossbars on both sides of the plants about 3 feet above the ground to confine the canes. If necessary, attach canes to the wires with twine. Another method is to train the canes along an existing fence. A third method is to tie the canes to stakes. For more information on trellising methods, see Small Fruit in the Home Garden.
HARVESTING AND STORING RASPBERRIES
Raspberries are ready to pick when they separate easily from the core. Harvest early in the day when temperatures are coolest and after the dew has dried. Because the fruits are fragile, layer them in shallow containers no more than 3 to 4 berries deep. Don’t wash the berries until you’re ready to eat them. Refrigerate the unwashed berries immediately in air-tight containers. If you pick more raspberries than you can use within the next few days, freeze them in a single layer on a baking sheet for a few hours. Once the berries are frozen, transfer them to freezer containers and store for up to 10 months.
Raspberries, particularly the black varieties, are subject to a number of viral and fungal diseases. Viruses are commonly transmitted to plants by aphids or nematodes. Once a raspberry plant is infected with a virus, remove the plant and destroy it.
Of the various fungal diseases — such as cane blight, gray mold, anthracnose, or Phytophthora root rot — Verticillium wilt is the most problematic for raspberries. A soil-borne fungus, it enters susceptible plants through their roots, spreads through the plant’s vascular system, and causes the leaves to die. Affected plants should be removed and destroyed.
To prevent viral and fungal diseases in raspberries:
- Purchase certified virus and Verticillium wilt-free planting stock.
- Avoid planting raspberries where other plants infected with wilt were previously grown.
- Space plants properly for good air circulation and exposure to light.
- Make sure the soil drains well to prevent root rot diseases.
- Mulch around roots to prevent fungal spores from splashing up on foliage.
- Replant with quality stock about every 5 to 7 years.
- Remove any wild bramble fruit plants from the vicinity of your garden.
- Remove and destroy pruned raspberry canes. Don’t add them to the compost pile.
Japanese beetles commonly flock to raspberry plants in mid-summer, skeletonizing leaves and chewing holes in the berries. At the first indication of damage, start hand picking the beetles early in the morning when they are sluggish and drop them into a pail of soapy water. Spider mites weave webs around the leaves and canes and feed on plant tissue by sucking out the plant juices. Their damage results in yellow spots on the foliage. A sharp spray of water or insecticidal soap should kill the mites. Cane borer damage is indicated by wilted raspberry cane tips. To prevent the borers from tunneling down into the canes where they will overwinter, cut off the cane tip about an inch below the wilted portion.
Growing raspberries is rewarding and easy to do. Although best eaten fresh right off the plant, they make a tasty, healthy addition to salads, desserts, and even savory dishes. Add them to fresh spinach or mixed green salads for a sweet-tart pop of flavor. Incorporate them into a mixed-berry fruit salad with blackberries, blueberries, and strawberries. Combine them with other salsa ingredients to serve with chicken or shrimp. For a sweet treat, bake them in muffins and enjoy with your morning tea or coffee. Make a fresh berry sauce to serve over ice cream or as an accompaniment for desserts with lemon or chocolate flavors. Blend frozen raspberries with peaches, mango or other fruits to make a nutritious, vitamin-rich smoothie. No matter how you use them, make raspberries an important part of your diet.
Homegrown Berries, Timber Press, 2014
“Small Fruit in the Home Garden,” Virginia Cooperative Extension Publication 426-840 https://www.pubs.ext.vt.edu/426/426-840/
“Japanese Beetle Pest Management in Primocane-Bearing Raspberries,” Virginia Cooperative Extension Publication 2909-1411 (https://www.pubs.ext.vt.edu/2909-1411)
“Raspberry Cane Borer,” North Carolina State Fact Sheet (https://content.ces.ncsu.edu/raspberry-cane-borer)
Oregon State University Berry Health Benefits Fact Sheets, (http://berryhealth.fst.oregonstate.edu)