How to Grow Blackberries and Raspberries
One of the greatest treats a gardener can grow are raspberries and blackberries. Pay close attention to pests like rabbits, birds, and small children so you have something to harvest this summer.
Blackberries (also Loganberry, Boysenberry, and Youngberry) grow best in fertile, well-drained soils and those soils that are in windy areas or areas of late spring frosts should be avoided. They are easily propagated by tip layering, which is done by inserting the tip of a cane in the soil in the fall, and digging up the young rooted stem the following spring. They are also propagated from suckers or root cuttings.
Plants are set 5—10 ft. apart depending on the training system used. The plants themselves should be planted as early in the spring as possible and cut back to about 8— 10 in. high after planting.
Blackberry canes are biennial, meaning they grow canes one year, produce fruit the next and then die, and should be removed. Varieties differ in the length of the canes. Some varieties, especially those grown in the eastern United States like ‘Darrow’, ‘Bailey’ and ‘Eldorado’, are mostly self-supporting but the loganberries and boysenberries, as well as some Blackberry varieties grown on the Pacific Coast have long trailing stems that must be trained on a trellis; otherwise they would fall to the ground.
If the planting is to be grown without a trellis, the plants should be spaced about 2—3 ft. apart in the row and the rows 8—9 ft. apart. Young shoots will come up between the plants, but cultivation should be used to keep these suckers to a strip of soil about 1 ft. wide. If this is not done the plants can become tangled and very difficult to manage since they have rigid thorns making any pruning difficult without thick gloves and long-handled lobbing shears are used. Mulching can be used, but the suckers coming up between the rows should be eliminated from time to time.
Pruning is best done in the early spring, removing canes that have borne fruits as well as any weak or broken canes. Those canes remaining (if no trellis is used and these are self-erect varieties) should be about 8—10 in. apart, and the laterals should be reduced to about 8—12 buds each. The new canes start growing rapidly in June and the tip of these should be pinched when the canes are about 2—3 ft. tall. This will have to be done weekly since the canes do not all mature at the same time. This will promote sturdy and compact plant development. When harvesting is over the old canes can be removed any time. Those varieties with long, trailing stems are usually trained to a wire trellis. Plants are spaced about 10 ft. apart and the canes tied to the wires. Some gardeners use a simple stake, one to each hill. The stake is about 5—6 ft. tall and the canes merely wrapped around the stake in spiral fashion and the ends clipped off at the top. The canes can be trained on single wires wrapped around them, or on 2 wires or tied in the form of a fan to several wires. This takes more labor perhaps but often results in a higher yield.
Image from University of Maine Cooperative Extension
Blackberries should only be picked when they are fully ripe and about to be used. They do not ripen all at once but over a period of several weeks in July and August, but will ripen earlier with warmer weather. They respond to the application of nitrogen fertilizers in early spring, but the amount should be controlled by shoot growth and fruit production.
Blackberry sawfly and raspberry sawfly may strip the leaves in early summer. They are easily killed with permethrin or carbaryl (e.g., Sevin). Red-necked cane borer kills many canes by boring in the pith. Careful pruning holds these in check. Blackberry psyllid and rose scale cause abnormal and weakened canes. Spraying with insecticide is effective. In the Northwest the blackberry mites cause the “red berry” disease. These gall mites overwinter in buds. Spraying with fungicide when canes are dormant is suggested. The tarnished plant bug can be a serious pest also, but can be effectively controlled by spraying the plants just before the first flowers. Cane borers sometimes produce irregular swellings or lumps (galls) in canes and infested canes are weakened and may die. They should be cut out and burned. Wild blackberries may have this insect and they should be dug out and destroyed if nearby.
These shrubs are among the hardiest of the bush fruits and are perfectly at home in the northern United States and southern Canada. The canes are biennial, as in blackberries, that is, they normally are produced one year, fruit the second year and then die and should be removed in the annual pruning that these shrubs require to keep them in good bearing condition. The new shoots either appear at the base of the plant or as suckers a foot or so from the plant. The also tolerate some shade so they can be planted near a structure or under taller trees.
There are 2 types of red raspberries, those that only fruit once a year, and those sometimes termed “ever-bearing” that fruit early in the season (July), have a few weeks rest, and then fruit again in September or until frost, After growing both types, I prefer the “ever-bearing” group better, for in a good growing season it does seem that we have fresh fruit from early summer to frost, with a break of about 2 weeks. However, some gardeners may not care for raspberries this much or may be away from home in early summer. The fruits of the “ever-bearing” types may not be as large or sweet as the standard varieties. Pruning the “ever-bearing” group is a little different because the same canes that bear in early summer bear again in the early fall. After fruiting in the fall, the fruiting canes can be removed, together with weak canes. This pruning can also be done in the winter or early spring.
Because they send up suckers some distance from the original plant, raspberries, like blackberries, might best be planted in the home garden to a strip about a foot wide. Shoots coming up outside this should be removed. This can easily be done merely with the mechanical cultivator, but using a dandelion knife is the simpler method.
Raspberry canes grow 5—6 ft. tall and, when loaded with fruit, they bend over to the ground, and are hard to pick. It is best to give them some support by tying each cane to a horizontal wire. If this is too much work install a series of strong posts, or PVC or metal pipes 20 ft. apart in a rectangle around the planting area. Run two sets of wires, one about 2 ft. above the ground, the other about 4 ft. above the ground. These 4 wires are the area where all the canes grow and are held upright. There is no need to tie each cane.
Images from University of Maine Cooperative Extension
There are only four items your need to remember when pruning raspberries or blackberries;
• Two-year-old canes are removed entirely.
• Topping one-year-old canes slightly.
• Remove weak canes.
• Remove unwanted suckers.
Pruning is completed in late summer for the single-crop varieties, or in the fall, winter or early spring for the “ever-bearing” varieties. Canes left may have the tops snipped off at about 4 ½ to 6 ft. high, depending on variety. The Black Raspberry and the Purple Raspberry are treated in the same manner, except that the shoots tend to be long and trailing and the ends might be cut off when they have reached their proper manageable height of 5—6 ft. This heading back should be done as soon as the growth reaches this height.
Propagation is accomplished by dividing the plants, digging up rooted suckers, or using a sharp spade through the center of a plant from which many canes have developed. The black raspberries are reproduced by tip layering, in which you select a long arching shoot, placing the tip firmly in the ground with just the end showing. This is done in late summer and by the following spring this should be rooted. Planting can be done in either the fall or the spring, but other things being equal, early spring is probably best. When properly planted, about 30—48 in. apart in the row for the raspberries and 3—6 ft. apart for the black raspberries, the canes are cut back to about 6 in.
Raspberry cane borer, red-necked cane borers and raspberry cane maggot all puncture and girdle the tips of canes and cause them to wilt. Spraying just before bloom with insecticide combined with fungicide prevents much injury, but careful pruning of wilted shoots is also necessary. Raspberry fruit worm is a beetle which eats holes in the first leaves and lays eggs in the blossoms. Small grubs feed in the developing berry. Spraying as above is recommended. Japanese beetle is attracted to Raspberry and spray or dust of insecticide, along with handpicking, should prevent significant loss. Red spider mites often reach the peak of abundance during harvest and a miticide spray just before the fruit forms and after harvest is advisable. For most pests, the insecticide permethrin or carbaryl (e.g., Sevin)
Mosaic resulting from infection by several viruses is the most destructive disease. Discolored, twisted, curled, abnormal leaves are the principle symptoms. Planting the more resistant varieties and careful removal of infected or suspicious plants is the only protection. Infected soil should be avoided for new plantings and any aphids promptly sprayed with insecticide #15. Leaf curl and streak are treated in the same way. Anthracnose may weaken or kill canes following the development of gray spots on the bark. Careful pruning and thinning of weak canes and application of a general spray schedule usually checks the disease. Cane blight and spur blight produce gray or purple blotches on bark which may kill the cane or the fruit spur. A dormant spray of fungicide or a general schedule is advised. A white powdery growth on the wilted tips of new canes indicates powdery mildew.