Our black Labrador, Molly, developed a taste for raspberries. She began grazing on the berries that dropped to the ground and worked her way up as far as she could reach if we didn’t watch her closely. And Molly’s not the only member of the family fascinated by the taste of this flavorful fruit.
Raspberries get their scientific name, Rubus idaeus, from a legend that claims Greek gods returned from Mount Ida in Turkey with these luscious berries. Considered a delicacy by many since they are so perishable, raspberries have been a part of my life for as long as I can remember. After growing raspberries, harvesting the fruit was one of my childhood chores growing up in northern Minnesota, and as a young married couple, my husband and I started our own raspberry patch with plants from my parents’ garden.
Lately, our raspberries aren’t doing as well as we’d like, and it’s no wonder. After interviewing raspberry expert Dave Wildung, retired horticulturist at the University of Minnesota North Central Research and Outreach Center in Grand Rapids, Minnesota, I understand why: We did almost everything wrong. Wildung warns home gardeners to avoid the “neighbor policy” of acquiring raspberry plants.
“Raspberries are very prone to virus diseases that are vectored by aphids,” he says. “Even when you buy certified disease-free nursery stock, there’s a limited time those plants are virus-free.”
Noxious diseases are present in most older raspberry patches, so our plants from my parents’ garden were almost certainly infected.
“Virus diseases are very hard to see,” says Wildung. “Once a virus disease gets into a plant, there’s nothing you can do to get rid of it.”
Crumbly berries are one sign of a virus, another sign is greatly reduced plant vigor, and the last is smaller fruit. Another mistake we made long ago was not preparing our bed in advance by getting rid of all perennial weeds like quack grass. And a third error was failing to remove all wild berry plants within 600 feet of our raspberry patch. Wildung says it would be very rare to find a wild plant that doesn’t have a disease.
When to plant raspberries and raspberry culture
Plant raspberries as early in the spring as you can obtain plants, and as soon as the ground will allow you to get into the garden. Raspberries prefer light-textured soil. The ideal is sandy loam or loamy sand. Do a soil test before planting, and try to add phosphorus and potassium according to the test results. The only nutrient they need after that usually will be nitrogen applied every spring before growth starts.
These perennials like plenty of water, and trickle irrigation works well unless you have sandy soil. One to two inches of water a week is a good rule to follow. Mulch lightly to improve organic matter, but be sure the mulch isn’t so thick that it restricts new cane growth. If possible, plant raspberries in full sun. Good air circulation is critical to prevent disease.
Two types of raspberries
There are two types of raspberries: summer-bearing and fall-bearing. The summer-bearing types need to be pruned every year, removing the old canes and pruning down the density of the new ones. Raspberry plants are unique in that they have perennial root systems that continue to grow, and they have a biennial cane system. The first year the cane is vegetative, and the second year it flowers, bears fruit and then dies.
Breeders at the University of Minnesota have been involved in raspberry evaluation for more than 80 years, and they introduced Latham, a popular summer bearer, in 1920. Boyne came along in 1960, and Killarney and Nova are more recent introductions.
A while ago, someone made a revolutionary discovery, according to Wildung — a plant that started to flower on the tip of the new cane. This find was the beginning of fall-bearing raspberries. Now most breeding programs are working with fall-bearing types because those canes can be cut down to the ground after harvesting and don’t require any other differential pruning. Mowing off the canes after harvest also eliminates the chance of winter injury.
Heritage was one of the first fall-bearing raspberry varieties, but it is too late for our short Zone 3 season. Autumn Bliss was a 1983 introduction from Great Britain, and it is two weeks earlier than Heritage. Wildung says the fall-bearing plants produce larger fruit than the summer bearers. To find out what type of raspberry is recommended for growing raspberries in your area, contact your county extension office or ask at local nurseries and garden centers.
Systems for pruning raspberry bushes
Two types of pruning systems are commonly used for raspberries. For our summer-bearing types, we planted four rows of raspberry canes about 25 feet long and 8 feet apart. We placed strong posts 10 feet apart in the rows with two sets of lateral wires, 3 1/2 and 5 feet high, on either side of the post. This system of training the plants is often referred to as the hedgerow or matted row system. We arranged the canes between the wires to prevent them from spreading.
“The key to pruning is to prune the density down to the point where at the base the row is no wider than a foot,” says Wildung, “and within that row continue to prune out the weakest canes so you get down to a density of eight to 10 canes per running foot of row.” Raspberry plants can become their own worst enemy if you don’t prune out enough canes. Some growers prefer the hill system, in which they tie the five to eight strongest canes in teepee fashion to a stake.
Rejuvenating raspberries
To rejuvenate our raspberry patch, every year, the old canes that have fruited are removed as soon as the harvest is over, leaving only the younger canes that are setting buds for next year’s crop. You can recognize the older canes by their grayish-brown color, peeling skin and brittle wood. Cut these canes off cleanly at the soil line. The healthy young canes are a shiny tan or purplish-red and generally won’t have any branches.
Every spring, we thin the new canes to 2 feet apart, taking care to remove any canes smaller in diameter than a pencil. Cutting the canes close to the ground promotes new growth from below the soil and avoids stubs that serve as entry places for insects and diseases.
We mulch with leaves between the raspberry rows to keep weeds to a minimum and hold the moisture that’s so important to a berry crop. We add compost or manure to each row in the fall so it has a chance to break down through the winter months. We also use nitrogen along the rows in early spring — about 1 pound per 25 feet.
Mow fall-bearing raspberries to the ground either after harvest in the fall or in early spring before growth begins.
High-tunnel raspberries
The use of high-tunnel greenhouses for growing raspberries is a growing trend. (For more on high tunnels, read The Benefits of Building a High Tunnel.) Last year, horticulturist Shengrui Yao, then working at the University of Minnesota North Central Research and Outreach Center, planted fall-bearing raspberries in a high-tunnel greenhouse, and she was amazed at the results. Some plants grew 7 feet tall and produced the equivalent of 16,000 pounds per acre in their second season. Many began bearing in early August and produced until November 2. Their cousins out in the field produced just a fraction of the fruit, the equivalent of 4,000 pounds per acre. Her favorite varieties for northern Minnesota’s Zone 3 climate were Polana and Joan J.
Yao recommends shoveling snow over the base of the plants during the winter months for additional protection and closing up the high tunnels. She also advises using a propane heater to maintain a temperature of 35 degrees F in the high tunnel for frost protection. Purchasing tissue culture plants from a reliable nursery is ideal. She pinched the most vigorous plants twice during the growing season so they bushed out and didn’t get too tall.
“In a climate like ours (Zone 3), high tunnels allow you to get earlier raspberry production, a much longer growing season and larger, better quality fruit,” says Wildung.
Raspberry lovers everywhere take note, and enjoy the fruit of your labors.
Margaret Haapoja grew up picking raspberries in her parents’ garden, and she has grown them for many years in her own garden, where her husband now tends the patch. She enjoys those luscious berries on her cereal every morning in late July.
Top summer-bearing raspberry varieties
Boyne: Very winter hardy with excellent fruit quality and good yields. Introduced in 1960 from Morden, Manitoba.
Killarney: Released in 1961 from the Morden, Manitoba, breeding program and a sibling of Boyne, slightly larger, but later maturing than Boyne. Excellent yields and good winter hardiness. Has outproduced Boyne in recent years.
Latham: Introduced from the University of Minnesota breeding program more than 60 years ago, this variety is widely adapted and has good yields and winter hardiness. It is susceptible to diseases.
Nova: Relatively new variety introduced from Nova Scotia, widely adapted, productive and winter hardy. Best yielding summer-bearing variety at the University of Minnesota North Central Research and Outreach Center in Grand Rapids.
— Bob Olen
Top fall-bearing raspberry varieties
Autumn Bliss: Begins bearing 2 to 3 weeks before Heritage. Yields 50 percent of its total crop during the first three weeks of harvest. Shows a tolerance to heat for southern growers. Fruit is large, dark-red with a pleasant, mild flavor. No. 1 fall-bearing raspberry in Indiana.
Caroline: Produces huge, very sweet, firm fruit. Ripens before Heritage and is a big producer. Plant resistant to root rot, making it suitable for a wide range of soil types. Vigorous growth habit and disease resistance as well as exceptional fruit quality make it a good choice for home gardeners.
Heritage: Hardy variety that produces two crops. The first is in July and the second is a fall crop beginning in September and bearing until the first hard freeze. Berries are large, brilliant red, extremely firm and attractive. Superb for freezing and delicious for table use. Fall crop is larger than the summer one. Rated the No. 1 fall-bearing variety.
Autumn Britten: Nice fruit, fewer canes, midseason, double berries. Originated in Great Britain. Ripens before Caroline and Heritage, bearing fruit from late summer through the fall. Very large, very firm and coherent berry that is flavorful. Winter hardy in trials at Nourse Farms.
Polana: At least three weeks earlier than Heritage, Polana allows you to grow fall varieties in more northern locations and still produce a great crop. Berries are highly productive, large, glossy in appearance, with good flavor. Canes are short and vigorous. Ripens early August in southern New England. A great choice for early fall raspberries. Polana needs extra fertilizer in May and June.
Joan J: High yielding, thornless, with large, flavorful fruit that hold their size well. Berries are firm, easy to pick (release well) and recommended when early fruit is required.
Protecting from theft
Netting is sometimes necessary to keep birds like robins from stealing some of the crop. Hornets often come in late in the season to feast on the berries. To deter them, be sure to keep the patch picked clean. Overripe fruit is going to be a drawing card.
Raspberry sources
Indiana Berry Farm
2811 U.S. Hwy 31
Plymouth, IN 46563-9196
800-295-2226
J.W. Jung Seed Co.
335 S. High St.
Randolph, WI 53956-1425
800-297-3123
Nourse Farms
41 River Road
South Deerfield, MA 01373-9615
413-665-2658
