Early in this century, black raspberries were just as popular as red raspberries. And no wonder! This jet black bramble, sometimes called a blackcap, has a rich, sweet taste. The berries are firm and not overly juicy. When you eat them fresh, their texture is a little thicker than red raspberries or blackberries. Their firmness also helps the fruit resist rotting better than other brambles, either on the plant or in your refrigerator.
Despite the black raspberry's past popularity and the fact that it will grow well from zone 4 south through zone 8, today the blackcap is mostly a regional favorite. The middle Atlantic region and Ohio are traditional hotbeds of black raspberry enthusiasm. There are a few commercial growers of black raspberries in the East, all with small plantings. The state that grows the most black raspberries is Oregon, with about 1,000 acres planted. Most of these berries are mechanically harvested for processing into jams, dessert flavorings and even a natural dye for meat. You may already enjoy black raspberries, but if you don't yet know them, you've got a real treat in store.
The black raspberry is a native fruit, growing wild along the edges of woods from Quebec to North Dakota, and south to Arkansas and Georgia. The first variety, Ohio Everbearing (small and not very tasty), was named in 1832. By the end of the 19th century, thousands of acres of black raspberries were being planted in western New York alone. In his 1925 classic, The Small Fruits of New York, Ulysses Prentiss Hedrick described almost 200 varieties of black raspberry, most of them selections from the wild. Today, however, only a handful of black raspberry cultivars are readily available.
Although named varieties of black raspberries do differ from one another in fruit size, firmness and flavor, the differences are not all that great. Nor are named varieties very different from good wild ones, with one important exception. Wild black raspberries are very lely to carry diseases. Nurseries, on the other hand, work diligently to produce plants that are close to disease-free.
Here are some of the best named blackcap varieties available today. Expect to pick between three and four pints per plant over the 10- to 14-day ripening period. Blackcap harvest starts at the very end of the strawberry season and a few days earlier than the first red raspberries. You'll get to taste your first berries a year after planting.
'Allen'. Bred in New York in 1947 and named in 1963, it ripens in a concentrated period, so nearly all the fruit can be picked at once. Bristol is one of its parents.
'Blackhawk'. Bred in Iowa and introduced in 1953, it is one of the hardiest varieties available and ripens about five days later than most blackcaps.
'Bristol'. Bred in New York in 1921 and named in 1963, it has become the most widely planted blackcap in the East.
'Haut'. Bred in Maryland by Harry Swartz, currently the most active blackcap breeder, and released in 1984, Haut ripens three to five days later and has a longer picking season than most blackcaps.
'Jewel'. Bred in New York and named in 1973, it is slightly late in ripening and is one of the most disease-resistant varieties. Bristol is one of its parents.
'Munger'. Developed in Ohio and introduced in 1897, it is still the leading variety for machine harvesting in Oregon.
Among the varieties listed in 1925, quite a few were everbearing or bore white fruits. In years to come, look for both of these traits to be reintroduced. Also look for complex hybrids of black raspberries and various species of other raspberries and blackberries, including some that are tropical and Asiatic.
Rule number one in growing black raspberries is: Don't do what I did! When I put in my first planting, I dug nearby wild blackcaps, then set them in a row with my collection of red raspberries. Not only are wild blackcap likely carriers of disease, but the red raspberries may be symptomless carriers of mosaic virus, which aphids can spread to nearby black raspberries.
Instead, purchase nursery-grown plants -- they're much less likely to carry diseases than wild plants are. Few nurseries can officially certify their plants to be virus-free because symptoms are not always obvious and there is not yet a convenient test that determines whether or not plants are infected with mosaic. But researchers are developing a virus test, so that in the future, virus indexing and tissue culture propagation can ensure disease-free nursery plants.
Plant blackcaps as far away as possible from red raspberries or other cultivated brambles, and remove existing wild berries if practical, or your new plants may soon pick up diseases. Black raspberries are susceptible to Verticillium wilt, so also avoid planting where other hosts of this soilborne disease -- such as brambles, tomatoes, peppers, potatoes or eggplants -- recently grew.
When choosing a site, pay attention to sunlight and soil. A sunny site promotes sweeter fruit and quicker drying of leaves, canes and fruits, which helps thwart fungal disease. The soil itself must be rich in humus and well drained, with a pH of about 6. One quarter pound of 10-10-10 (or another fertilizer with an equivalent amount of nitrogen) per plant will get young blackcaps off to a good start. A third of a pound of soybean meal is a good organic alternative. Spread the fertilizer evenly over the surface of the planting bed and work it in shallowly. Most of the roots of black raspberries grow in the surface layers of the soil, so blanket the ground with a thick organic mulch such as leaves or straw.
Space plants three feet apart in the row, with eight feet between the rows. Right after you plant, lop all canes back to the ground, just in case they have any diseases on them. You don't have to worry about plants spreading underground like red raspberries, because most nblack raspberry shoots arise right at the base of the plant. Black raspberries do spread in their own way, however. They take root wherever the tips of arching canes reach down and touch the ground. Don't allow those tips to root unless you want to propagate new plants.
1. Raspberry canes are biennial, growing stems the first season, then fruiting and dying in the second season. So the first step in pruning is to cut the canes to the ground right after they finish fruiting. They'll soon die anyway, and removing them admits more sunshine to the new canes growing from the base of the plant. Finish pruning old canes before plants leaf out in spring.
2. In the summer, when the new canes reach about 20 inches tall, pinch out the top two inches to keep them at 18 inches. Do this weekly for several weeks until all the new canes (primocanes) have reached the desired height and been pinched back.
3. The summer topping described in step 2 stimulates growth of side branches, which will fruit the following season. Pinching back at 18 inches keeps the plants stocky enough that you won't need a trellis. (Alternatively, you could run a single wire above the row at about three feet. Delay pinching until the canes are tall enough to be tied to the wire.)
4. In the dormant season, preferably just before growth begins in spring, thin out canes, removing any that are diseased, damaged or spindly. On remaining canes, shorten the side branches proportionally to their vigor. The largest side shoots can be 18 inches long, and the thinnest about six inches long.
Black raspberries fall prey to a number of diseases. Orange rust is a fungus that produces decorative but deadly splotches of orange spores on the leaves. Anthracnose fungus can also be debilitating, attacking black raspberries more readily than red raspberries. The weakened canes, spotted with purple-margined gray lesions, are susc to winter cold damage and produce dried-up fruits. Black raspberries also are very susceptible to mosaic virus. In its advanced stages, mosaic causes mottled leaves as well as stunting, and even death, of a plant.
Disease problems of black raspberries vary from site to site. "Some plantings get rust, while others do not," says Dr. Harry Swartz, a breeder of black raspberries at the University of Maryland. "I could not get infection in my test plots on young or old plants even after dusting them with the contents of a one-ounce bottle of spores that I had collected."
In a test planting of black and red raspberries during two wet years, Pennsylvania State University's Dr. Barbara Goulart found that the blacks outyielded the reds, in spite of the blacks' higher susceptibility to anthracnose. Even mosaic infection is unpredictable. Some commercial plantings in New York become unproductive within three years because of mosaic virus while other plantings seem unaffected. Farther south and in the Pacific Northwest, mosaic is less common. The Pacific Northwest does have its share of Verticillium, though.
The first line of defense is to obtain clean plants from a nursery. Then select a site with the good drainage and the ample sunlight that raspberries like. Prune to encourage air circulation and remove diseased canes.
If anthracnose becomes a problem, spray the plants with lime-sulfur solution at budbreak and, if needed, during the growing season. Always keep an eye out for orange rust and mosaic virus. Pull up and burn any plants you suspect carry either disease. Even with clean plants and a clean site, a black raspberry planting will eventually decline from a buildup of pests, so don't be surprised if you need to replant at a new site in 5 to 10 years.
Article published on June 23, 2008.