Blackberries grow wild in northern Florida and can be easily grown in all parts of the state. When planting several plants, choose different varieties to encourage cross-pollination. Remove suckers regularly to keep the plants from spreading out of control. Most blackberry varieties have thorns, so gloves are recommended when harvesting or working with blackberries.
Choose a well-drained site with good air circulation and plenty of sun. Blackberries prefer full sun, but can tolerate some shade. Remove all grass and weeds. Dig the soil to a depth of 1 foot. Check the soil pH and adjust it to between 5.5 and 6.5 if necessary.
Plant bare-root blackberry plants in the winter; between December and February is best. Dig a hole large enough to accommodate the roots of the plant when spread out.
Place the plant in the hole at the same depth that it was originally planted. Fill the hole with soil and tamp it down. Provide a trellis or fence support for trailing varieties.
Plant the blackberry bushes 3 to 4 feet apart in rows that are 10 to 15 feet apart. Water the bushes immediately after planting. Water the plants every other day during the dry months. Consider using drip irrigation. Drip irrigation conserves water, reduces weed growth and keeps the leaves dry.
Apply a layer of organic mulch. Mulching helps conserve water and reduces weed germination. Remove weeds as they appear, either by hand pulling or by shallow hoeing. Blackberry roots are shallow and easily damaged by vigorous cultivation.
Protect plants from frost once the flowers appear. Cover the plants with cloth or plastic on cold nights, or turn on the sprinklers until all danger of frost is past.
Fertilize blackberries in the late spring or early summer of the first year. Apply 4 oz. of 10-10-10 fertilizer per plant. Fertilize in the winter and summer in subsequent years.
Remove suckers as they appear. During the first year, cut off the tip of the elongated shoots to encourage branching and budding. These branches will produce fruit next year.
Prune blackberries after fruiting. Remove dried and dead canes at the crown. Prune the entire bush to a height of 1 foot every 3 to 4 years. This will reduce fruit for the year, but it renews and invigorates the plant for future years.
Hand pick blackberries twice a week as they ripen. Berries are ripe when they change color from red to black. Refrigerate berries immediately after picking.