Blackberries

Blackberries are a great addition to your backyard garden. They are easy to grow, produce plentiful fruits that are highly nutritious and very healthy. In fact, blackberries are one of the fruits with the fruits with the highest antioxidant content. Blackberries are very versatile, being consumed fresh, prepared as jellies or as desserts such as cobblers or pies.
There are three classes of blackberries: trailing, semi-trailing, or erect. The trailing varieties (sometimes referred to as dewberries) are thorny, the semi-trailing varieties are thornless, and the erect varieties are thornless or thorny. As a general rule, the erect varieties are more cold-hardy than the semi-trailing or trailing varieties.
Semi-training blackberry varieties should be planted 6 to 8 feet apart in a row, with rows 10 feet apart. Trailing varieties are less vigorous and should be planted about 4 feet apart with rows to 8 feet apart. Erect varieties are normally established by planting root cuttings that are planted about 2 feet apart. Plant blackberries in early spring, about 4 to 6 weeks before the last frost. When planting, make sure the crown is planted 2 inches below the soil line. Spread the roots carefully. Prune old canes back to 6 inches.
Mulch aids in water retention and weed control. Mulch with pine straw or bark. Blackberries are quite drought-hardy, but require considerable water during the fruiting period. Apply about 1 inch of water per week by irrigation if rainfall is not met.
Fertilize blackberries in the early spring when growth starts and again just after harvest. During the first year or two of growth, apply the fertilizer in a 12-inch circle around the plant. On older plants, broadcast the fertilizer down the row.
Blackberries have crowns that produce biennial shoots (live for 2 years, then die). During the first year of growth the shoots are called primocanes. These primocanes develop flower buds the first year of growth. In the second year the shoots are called floricanes. These floricanes produce flowers that mature into fruit. After fruiting these floricanes die and should be removed.
Trailing and semi-trailing varieties need support by a trellis or similar structure. Using a two-wire system with wires at 3- and 5-feet high works well. As the shoots emerge in the spring, tie the shoots to the wires in a fan-shaped pattern. Do not top the canes during the growing season. The old floricanes should be pruned out and discarded during the dormant season.
Train unpruned erect varieties to a one-wire trellis. Erect varieties do not need support if the primocanes are pruned during the summer to keep the canes from growing more than 3 to 4 feet in height. When the shoots are 30 to 36 inches tall, cut off the tip to promote branching. After harvest, cut and remove all floricanes. During the winter, prune the laterals to 12 to 14 inches for easier harvesting and larger berries.
Blackberries are ripe and are at peak flavor when they begin to lose their glossy shine and turn slightly dull. Trailing and semi-trailing varieties begin to ripen in early June. Erect varieties ripen about two weeks earlier than trailing or semi-trailing varieties. Harvest will cover two to three weeks.
Blackberry insect problems are minimal. General pesticides can control aphids, Japanese beetles, and spider mites on an as-needed basis. Chemical controls are not available for crown borers. Diseases include rust, fruit rot and “double blossom”. A fungicide program can control fruit rot and be a preventative program for rosette. If severe infection occurs, summer mowing of all canes down to the ground will reduce infection of later emerging primocanes. Leaf and cane diseases are controlled by the use of copper, lime sulfur or Bordeaux. Apply all chemicals according to directions on the label.
A variety trail carried out at Clemson University Musser Fruit Research Farm showed the highest yields under their conditions were Natchez, Navaho, Von, and Osage, followed by other such as Triple Crown, Ouachita and Arapaho. Navaho and Ouachita had some of the highest brix (sugar content) and Prime-Ark® Freedom, a primocane-fruiting variety, had bigger fruit size.
For more information on blackberries, please visit the Home and Garden Information Center website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7pm on SCETV or mig.org. Email Outen at [email protected]
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