It is possible to grow blackberries in Florida, blackberries actually prefer warm, temperate climates as they can be damaged by cold. Perhaps you were confused by their chilling requirement? That is the the time required for the plant to be at low temperature in order for the plant to flower in the spring. You should choose a variety of blackberry based on the number of hours of cold weather you will experience over the winter. Check this with the nursery from which you buy your plants to ensure you purchase the correct variety.

The plants should typically be planted between December and February so you will have to work fast if you want to pull it off this year, otherwise wait until later in the year. Blackberries should be planted in a sunny spot in the garden in well draining soil with a pH between 6.0 and 6.5. Plant bare root plants (plants that come with their roots exposed instead of planted in soil) approximately 1 ft deep by digging a hole large enough for the root ball with enough room for some spread (see the blackberry propagation section here on PlantVillage). In addition, blackberries often produce trailing vines and a trellis may need to be constructed. Growing them next to a fence may also be helpful.