Blackberries are a deciduous crop that thrives in the temperate climate of the southeast. While several blackberry species are native to Florida, wild blackberries tend to produce smaller berries with lower yields compared to improved varieties. Blackberry cultivars ripen during May and June, and due to their easily perishable nature are an ideal crop to produce for local markets.
Good drainage and air circulation are a must for successful cultivation of blackberries. When selecting a planting site, avoid low-lying areas to reduce opportunities for flooding and frost injury. Plant in full sun and maintain a pH between 5.5 and 6.5.
The ideal planting time for blackberries is during the winter months of December through February. When using bare-root plants, keep the roots moist, plant at the same depth as they were planted in the nursery, and prune the shoots to around 6 inches. Spacing will vary according to cultivar, but in general, space erect cultivars 3 feet apart and trailing cultivars 5 feet apart.
Blackberries have low fertilizer requirements and, due to their shallow roots, can be easily harmed by excessive fertilizer. Apply a 10-10-10 N-P-K with micronutrients during late spring or summer after initial planting, utilizing ¼ pound per plant or 5 pounds per 100 foot row; do not apply fertilizer in winter of initial planting. During second year and beyond, use ¼ to ½ pound per plant, or 10 pounds per 100 foot row, during winter and summer following harvest.
Proper irrigation and weed control are critical during the establishment year. Drip irrigation is recommended as it does not wet the foliage or stimulate excessive weed growth. Irrigation frequency depends on the water-holding capacity of the particular soil. Use organic or plastic mulch to conserve water and control weeds.
Proper pruning is essential for successful blackberry plant establishment. Blackberries produce two types of growth: primocanes and floricanes. Primocanes are first year shoots that do not produce berries. They become fruit-bearing floricanes the second year.
It is recommended to prune the tips off primocanes of erect or semi-erect bushes once they have reached a height of 30 to 36 inches in order to promote lateral branching. For trailing blackberries, tip when 40 to 48 inches. Tip early in the season to ensure formation of flower bud initiation is complete before winter dormancy.
Floricanes will desiccate and die once fruiting is complete. It is essential to completely prune out the floricanes immediately following fruiting to reduce disease pressure.
Harvest season for each blackberry cultivar lasts about 3 to 4 weeks. To extend your season, plant cultivars with various ripening dates. Blackberries are ready to harvest when they change from red to black, and are very perishable. Pick in morning or evening when temperatures are low, and refrigerate immediately at 32° F to 40° F.
Blackberry bushes can be erect or trailing and with or without thorns. While blackberries vary from self-fruitful to self-unfruitful, most erect blackberries are self-fruitful and therefore do not require a pollinator. Many of the newer blackberry cultivars, notable by their Native American names, come from the University of Arkansas and have been trialed by the University of Florida. The following cultivars are recommended for north Florida: ‘Apache’, Arapaho’, ‘Chickasaw’, ‘Choctaw’, ‘Kiowa’, ‘Natchez’, ‘Quachita’, Osage’, ‘Oklawaha’, Floragrand’, and ‘Brazos’.
Reference: The Blackberry: http://edis.ifas.ufl.edu/hs104