By Roberta Bailey
When the strawberries are ripe, they are the best berry; then come the raspberries, their less acidic, more delicate flavors convincing me that they reign supreme; but full summer brings the deep purple blackberry borne on fierce red canes, and when one waits for the shiny black fruits to soften and dull in sheen until they drop into the hand, the rewards are great, perhaps the greatest.
Blackberries are odd. In many locations, turn your back and they will over-run the farm. Yet few cultivated varieties are hardy enough to survive Maine winters. Horticulturist Lewis Hill says that hardy varieties are no longer available. Perhaps the good patches so many of us know of have escaped from old hardy farm plantings. ‘Mini Hardy’ and ‘Darrow’ are the two hardiest commercial varieties available. Hardy ‘wild’ patches with good fruit and no sign of disease may be the best source of plants. Both erect and trailing cane varieties are common. Erect varieties tend to have better flavor and need no trellising.
The crown of the blackberry plant is hardy to 40 below zero. The canes are much less hardy, as they are susceptible to northern winter’s drying winds. Choose a site that is protected from the winds arid where the snow will build up, insulate the canes and prevent them from dying back. Fruit ripen best on a cool northern slope versus a sunny southern slope.
Blackberries, like all brambles, have a perennial root system that produces biennial, reddish canes. The first year canes, called primocanes, are vegetative. In their second year, these canes, now called floricanes, bear fruit. Shortly after bearing fruit, they die. The root crown also grows new primocanes every year. If well-maintained, a blackberry plant will live for 10 years.
Site Preparation and Planting
Blackberries are fairly shallow-rooted. They adapt to many soil types but thrive in well-drained, humus-rich loam or sandy loam. Avoid heavy, wet, clay soils. The roots will not tolerate saturated soil or standing water. A pH of 6.0-7.0 is ideal.
Consider preparing a site one year in advance. Brambles do not compete well with grass or weeds. A nitrogen-rich, weed-smothering cover crop will add the necessary fertility and organic matter while eliminating weeds. Plan to mulch the established patch annually.
Once you have chosen a site, prepare the soil deeply, adding as much humus as possible. Compost, well-rotted manure and alfalfa meal are excellent choices. Blackberries also require phosphorous and potassium for fruit ripening and to help harden the canes in fall. Test your soils and add amendments as needed.
Blackberry plants are sold bare-rooted, in pots, and as tissue cultures, usually rooted in small soil plugs. Bare-rooted plants should be soaked for a few hours then either heeled into a trench or planted in their new bed. Plant as early as the ground can be worked, but not at the wet mud stage. Do not expose blackberry roots to direct sunlight. Sunlight significantly increases plant mortality. Cover the roots with a bag or cloth.
Potted plants can be planted at any time. Loosen their roots before planting. Tissue cultured plants that are green and growing will need to be potted and hardened off before being set out. If fully dormant, they can be cut back to the ground and set out.
Plant on a cloudy, windless day to reduce stress. Water in with a fish emulsion solution. Keep the shallow- rooted plants well watered throughout their first season. They need at least 1″ per week. Water is also needed in the three to four weeks preceding harvest. Plants should be spaced 2 to 4 feet apart within rows, with rows 6 to 10 feet apart.
Unlike many tree fruits, brambles require nitrogen in their first year to promote shoot growth. One month after planting, add a 2-foot-wide circle of nitrogen-rich food around each plant, but keep it 3 to 4 inches from the crown to avoid burning. One-half pound of elemental nitrogen per 100 foot row is the recommended rate for the first year. Application rates increase to 3/4 pound in the second year and 2 pounds in the third and all following years. An early spring (before mid-May) application of 60 to 100 pounds of well-rotted manure per 1000 square feet will supply the nutrients needed each year.
Mulch the bed heavily with wood shavings, bark chips, leaves, lawn clippings, seaweed, or other roughage. Sawdust tends to compact too much. Cardboard, black plastic, old carpet or metal roofing used as a layer underneath the mulch between rows deters weeds as well as unwanted suckering. As the mulch around the plants breaks down, it will help feed the plants.
No pruning is needed the first year. The second spring, feed and add mulch as needed. Thin out weak canes, and thin the primocanes to 6″ apart. In a 12-inch wide row, the ideal spacing is 4 to 6 canes per linear row foot. Tip the primocanes at 3 to 4 feet. Cut the laterals back to 12 to 18″ while they are still dormant. In fall, remove and burn dead floricanes.
In the third and following years, feed and mulch. Prune out broken branches. Remove sick plants and suckers growing in the wrong places. In late summer, thin canes to 6″ apart. In fall, cut back primocanes to 4 to 5 feet for winter.
Blackberries tend to be healthy plants especially when well maintained. A few diseases deserve vigilance. Orange rust shows itself as bright orange spores on the underside of leaves. As the rust is a systemic disease that spreads through the plant, infected plants must be dug and destroyed. Blackberries are also susceptible to anthracnose. Look for small, ash grey spots on the canes near the base of the plant and on leaves and fruit. Avoid planting anthracnose-prone crops near blackberries. These include sweet peas/beans, cucumbers, raspberries and grapes.
A partial crop of berries can be expected in the second year and a full crop in the third. Erect blackberries yield 3 to 6 pounds of fruit per plant. Trailing varieties can yield as high as 20 pounds per plant. Fruit ripens 40 to 60 days after bloom, which is late July or early August in Maine. The harvest period lasts four to five weeks, with fruit needing to be picked every two to three days.
Blackberries are best when just past their firm and shiny stage, when they get soft and dull looking and very sweet. If picked too early, they will be tart.
Blackberry fruit is very tender. Pick the fruit into shallow containers and keep them in the shade. If left in the sun, they can lose color and become sour. Pick in the cool of morning, handling as little as possible, then chill and process readily. Blackberries can be frozen as is. They can well in a light syrup and make excellent juice, wine, jelly, jam and syrup. I’ve become particularly fond of blackberry juice mixed in apple cider.
Hill, Lewis, Fruit and Berries for the Home Gardener, Storey Communications, 1992.
Otto, Stella, The Backyard Berry Book, Oncographies, 1995.
Rodale, J.I. and Staff, How to Grow Vegetables and Fruits by the Organic Way, Rodale, Inc., 1961.