Blackberries grow well in zones 4 to 9. Choose hardy, virus-free plants cultivated to your specific growing zone. Because varieties have different growth habits (upright or trailing), plan ahead to create a training and support system to match the variety you select. Blackberries are self-fertile so you can plant just one cultivar and harvest a crop-usually 10 to 15 pounds of berries per season per mature (2 to 3 year-old) plant.
Blackberries need at site that provides full sun and well-drained soil. Ideally the soil should have a slightly acidic pH (about 6.0). Domestic cultivars should be planted at least 300 feet away from their wild counterparts. Erect trellises or other types of supports before planting.
Erect blackberry varieties should be spaced in 3 foot intervals with 8 feet between each row. Trailing types should be spaced 5 to 8 feet apart with 6 to 8 feet between rows. The plants themselves should be planted to a depth about 1 inch greater than they were at the nursery. Apply a thick layer of organic mulch to the base of plants.
Care & Maintenance:
Blackberries may need maintenance pruning after the first season. Pinch off the tips of new canes when they reach 3 feet (or the top of the trellis for trailing types). After harvesting berries, cut fruit bearing canes to the ground. Apply a fertilizer (5-10-10 or 8-8-8) around fruit canes each spring. In the winter, thin canes so that only 4 to 6 remain per row (8 to 10 per plant for trailing varieties) and shorten all side branches to 12 to 18 inches. Canes from trailing types should be laid on the ground in the winter and covered to avoid cold damage.
Harvesting & Storage:
Blackberries ripen according to the variety grown and regional growing conditions, usually starting in mid-summer and continuing on through mid-fall. Collect berries every few days when fully ripe as they will not ripen off the stem. Ripe fruit will feel soft once it is pulled away from the plant. Pick the berries in the morning while it's still cool and remove any rotting berries at the same time to reduce the spread of mold and disease. Blackberries are delicate and should be handled gently to avoid crushing. Store them in a shallow container in the refrigerator immediately after picking. They are very perishable and will stay fresh for only one to two days at normal refrigerator temperatures, but will keep a day or two longer at cooler temperatures (31 to 32F ).
By Ellen Brown