The Blackberries of North America and Europe are a mighty clan of innumerable species and hybrids that have taxed the efforts of botanists to classify them. The many species in North America have furnished varieties suitable for cultivation in most of the United States except the cold, dry Great Plains region, and for the milder portions of Canada. One European species, the Cut-leaved Blackberry, Rubus laciniatus, has run wild on the Pacific Coast where it is cultivated.
Blackberry growing began in the eastern United States about 1850, when wild selections were brought into cultivation. Blackberries are not grown much now in the East, but Texas, Oklahoma and Arkansas have substantial acreages in commercial production.
Ripe Blackberries are a delicious fruit and provide home-grown berries after the Raspberries have finished. If plants of good varieties, true to name, are planted and the Tarnished Plant Bug is controlled, Blackberries may be grown successfully on suitable soils in many parts of North America. The erect, or bush type Blackberries are discussed here first; the trailing varieties are treated separately at the end of this presentation under a special heading.
Blackberries are less hardy than Raspberries, but the hardier varieties may be grown in the milder portions of the northern United States and Canada. Southward there are varieties suitable for the milder climate and the long hot summers. Winter injury of the Blackberry is chiefly from severe cold, rather than from the breaking of dormancy in mild weather, which causes so much late winter or spring-killing of Raspberries.
The site should be protected from the prevailing winds which dry out the canes in winter, a factor in winterkilling. Winds also dry out the soil in summer. A sloping site is preferable as it is not so cold in the winter, nor so subject to frost as low spots surrounded by higher ground. Wild Blackberries may harbor Orange Rust Disease, and, in the South, Rosette (double blossom) Disease, as well as insect pests. These wild plants should be eliminated near gardens, as they may complicate insect and disease control in the cultivated planting.
The soil should be a good farm or garden soil, not extreme in texture, and well supplied with organic matter. Deep, sandy loams are ideal, but clay loams will do very well if well managed. Good drainage is essential as Blackberries will not tolerate wet feet. The water table should not be nearer the surface than 3 ft. for more than a day or two during the growing season.
Blackberries are propagated from suckers which are produced in large numbers, and from root cuttings. The roots are dug in the fall, cut up in 4-in. lengths, stored in moist sand or peat over winter and planted out in nursery rows in the spring. In the fall they are large plants ready for planting.
Varieties of the bush type grown in the North are badly mixed in the trade so that it is very difficult to get plants of Eldorado and a few others true to name. Plants of known good performance should be used if available locally.
Eldorado, in the northern states, has long been the standard variety. The new varieties Bailey and Hedrick are similar types that have promise for New York and places with comparable conditions. Eldorado is resistant to Orange Rust. Snyder is one of the hardiest, but the berries are small and not of high quality.
The Evergreen Blackberry(Black Diamond) is grown in Oregon, Washington, and New Jersey. The plants are vigorous, semi trailing and productive of late-ripening fruit. They are usually grown on a trellis or stake. A thornless sport is available.
Himalayais a very vigorous semitrailing variety of the European Blackberry, Rubus procerus, that grows well in California. Brainerd, a hybrid of Himalaya, does well south of New Jersey and is grown commercially in Arkansas and western Oregon. In Texas and Oklahoma, Dallas, Early Wonder, Lawton and Haupt are popular. McDonald is grown in the Gulf region and Early Harvest generally in the South. Crandall is the leading variety in southern California.
Blackberries may be set either in the fall or early spring. The plants are set in rows 8-9 ft. apart, and 2-3 ft. apart in the row. The sucker plants will soon fill in the row, making a hedgerow which should be kept narrow for ease in maintenance.
Summer care consists of keeping down weeds by cultivating as shallowly as possible to prevent injury to the roots. A summer mulch is excellent, but the suckers will grow through it and must be removed at intervals or the planting will soon become an unmanageable thicket of Blackberry canes. The hedgerow should be kept about 1 ft. wide. After harvest, or about August 1st, cultivation should be discontinued and a cover crop sown between the rows. This is turned under or disced in the following spring.
Blackberries may be expected to respond to a nitrogenous fertilizer. Ammonium nitrate, or nitrate of soda, to provide about 60 pounds of nitrogen to the acre, may be used. This will take about 200 pounds of ammonium nitrate or 400 pounds of nitrate of soda. Other materials to supply the same amounts of nitrogen may be substituted. Stable manure, if available, is always excellent, but it should not be used to excess or the plants will make too lush a growth and suffer from winter injury. Some judgment must be exercised in fertilization as soils vary greatly in fertility and it is easy to overfertilize.
Blackberry canes of the hardy temperate zone varieties are biennial; they grow one season, bear fruit the next and in turn are replaced. The roots live on indefinitely, sending up new canes each year from the crown and from roots at a distance from the crown. If not restrained, they will spread many feet from the original.
Pruning, How to Do It. The new shoots are cut off (topped) at a height of 3 ft. as soon as that height is attained. The topped shoots develop strong branches, as a result, rather than grow very tall. The following spring, while still dormant, these laterals are headed back to 18-24 in. At this time the weaker and broken canes are removed, leaving a row about a foot wide. The canes which have fruited are cut out after harvest, or any time thereafter until the following spring. On dry soils the pruner must reduce the crop by cutting off fruit buds, and on moist soils more fruit buds may be left.
The home gardener should let the berries become fully ripe before picking them. A fully ripe Blackberry is a very delicious fruit. Berries that go to market are picked before they are fully ripe and are sour and hard. After picking, they should be moved to a cool, shady spot, as they soon turn red in the sun.
Trailing Blackberries include the Dewberries as well as the Loganberry, Youngberry, Boysenberry and other recent trailing hybrids. Varieties in this group have weak canes that sprawl on the ground and are grown on trellises or posts. They may be propagated by tip layering, whereas the erect Blackberries are increased from suckers or root cuttings. The plants are usually less hardy than the hardiest Blackberries, and they are mostly grown south of the latitude of Washington, D. C., and in the Pacific Coast states, where substantial commercial acreages are found.
The trailing Blackberries have the same soil and cultural requirements as the upright Blackberries, which are dealt with earlier in this article, but require a warmer climate and must be grown on trellises, or posts.
Varieties. The Loganberry, once widely grown on the Pacific Coast, is now being replaced by the Boysenberry and Youngberry, which are similar, but superior varieties. Loganberry plants are vigorous and very productive of large, dark-red, tart berries suitable for canning, freezing, and for juice. A thornless sport is available.
The Youngberry grows well south of Washington, D. C., and west of the Cascade Mountains on the Pacific Coast. The berries are large, deep wine-red, much sweeter than those of the Boysenberry and Loganberry, and ripen 10 days earlier than the Boysenberry. The thornless variant is considered to be less productive.
The Boysenberry is the most recent of this group and is replacing the others because of its greater productivity. The plants are vigorous and productive. The berries are very large, dark red, soft, tart and suitable for canning, freezing, and for jam and juice. This berry has been tried in the northern states, where it requires winter protection, but generally it does not produce much fruit there.
Cascade, Pacific, Chehalein, and Olallie are recent new trailing Blackberries of Oregon origin that are promising for trial in the Pacific Coast trailing Blackberry areas.
Lucretia, usually referred to as a Dewberry, is a vigorous, productive plant that bears large, jet-black, tart, early-ripening berries. It is grown chiefly in North Carolina and has been grown a little in the Hudson Valley of New York and in Michigan. Mayes, another Dewberry of Lucretia type is the leading variety in Texas.
Advance, grown in Florida and southern California, consists of a mixture of two clones, and each requires cross-pollination. The berries are large, very firm, good and very early.
The trailing Blackberries are propagated by layering the tips of the new canes. The tips are inserted vertically in the soil to a depth of 2 or 3 inches in late summer and fall. In the spring they are severed from the mother plant, dug and used for field planting. Root cuttings are also used for propagation as with the erect Blackberries. The thornless sports should be propagated by tip layering to perpetuate the thornless type. Plants grown from root cuttings of the thornless types will be thorny.
The trailing Blackberries are all grown on supports to keep the fruit clean and to aid in harvesting. In North Carolina, the Lucretia variety is grown on 5-ft. stakes set 5 ft. apart each way. In North Carolina, all of the canes, new as well as fruiting, are cut off at ground level immediately after harvest to aid in controlling fungus diseases. During the remainder of the growing season enough cane growth is made to produce a crop the following year. In the spring the canes are gathered into a bundle, wound around the stakes spirally and tied in 2 or 3 places with soft string.
In Michigan, Lucretia is set 21/2 feet apart in rows 7-8 ft. apart and the canes are tied to a single wire about 21/2 ft. from the ground.
On the Pacific Coast a two-wire trellis, or sometimes a single-wire trellis, is used. The wire is about 5 ft. from the ground, and with the two-wire trellis the second wire is 2 ft. below the top wire.
The plants of Boysenberry, Youngberry and varieties of similar vigor are set 8-10 ft. apart in rows 8-10 ft. apart, depending upon the tillage machinery to be used. The rows may be closer where a garden tractor or hoe is to be used.
The new canes are trained along the ground under the trellis to keep them out of the way of tillage tools and the pickers. U-shaped wires or short stakes hold them in place. After harvest the canes that bore the crop are cut out.
In late summer or autumn or in early spring, the canes are trained to the trellis in various ways. With a single-wire trellis the canes are taken up and twisted along the wire in one or both directions from the plant. With the two-wire trellis the canes are raised to the top wire, twisted around it, brought down to the lower wire and back to the plant. Some tying is done to hold the canes in place. In another method the canes are extended in each direction along the single wire, or along both wires in the case of the two-wire trellis.