Blackberries grow in two distinct forms; both bear fruit in summer. The canes of both kinds begin growth in one year, then produce a crop in the second year; they then die (to be replaced by new canes).
Blackberry varieties from the midwestern and eastern states tend to be the erect sort: hardy, stiff-caned plants that grow upright to 4 to 6 feet. Both erect blackberries and semierect types (crosses between erect and trailing types) succeed in Zones 1-9, 14-41.
Blackberries commonly grown in the West tend to be trailing. Some of these are so distinctive that they have separate names ― boysenberry, loganberry, marionberry, olallieberry. In the South, trailing kinds known as dewberries are often grown. Trailing blackberries are hardy in Zones 4-9, 14-24; some types succeed in Zones 28-32.
Planting and care
Plant erect blackberries 2 to 3 feet apart, allowing 6 to 10 feet between rows. Trailing blackberries need more room; set them 4 to 6 feet apart and allow 9 to 10 feet between rows. After planting, cut back canes of both kinds to 8 to 10 inches long.
In areas with very cold winters, blackberries that are marginally hardy for your area should be mulched heavily over winter. Bury the first-year canes (those that have not yet produced a crop) under a layer of straw, leaves, or cut conifer branches.
Pests and diseases
Blackberries are susceptible to verticillium wilt, so don’t plant them where you have grown potatoes, tomatoes, eggplants, or peppers in the last 2 years. Prevent problems by buying healthy stock and, if possible, resistant varieties.