Can a Bruce Plum Tree Grow in Southwest Florida?

Chilling Hours

• All trees that drop their leaves in winter require a resting period, triggered by cold weather and short days, to prepare for the coming year. After this period is fulfilled, the tree breaks dormancy and starts its growing season. In fruit tree production, this period of cold, known as chilling hours or chill units, holds special importance. Chill units measure the number of hours temperatures stay between 45 and 32 degrees Fahrenheit. Hours below 32 degrees don't count toward the total, and hours above 60 degrees impact it negatively. During the period of winter dormancy, trees need sufficient chill hours to bear fruit in a timely manner. Plums requiring high chill hours will fail to break dormancy properly in Florida's low-chill areas.

Bruce Plum

• Resilient and flavorful, Bruce plums originated from a cross between North American native plums and Japanese trees. Ideal for low-lying, frost-prone areas, Bruce exhibits excellent cold hardiness and is suitable for Florida's USDA zones 8 through 9. It has an attractive semi-dwarf, weeping habit and sweet, sunset-colored fruit. However, Bruce plums require 500 chill hours per winter dormancy season. In Florida, that occurs only in the northern-most section of the state. While the tree would grow farther south, its chill requirements wouldn't be met and it likely would not bloom or set fruit. Growing in southwest Florida's USDA zone 10, where annual chill hours range from 0 to 210, Bruce would struggle. Not getting enough winter dormancy leads to a weakened tree, and possibly early death from insects and disease.

Gulf Series

• In response to the need for plums adapted to Florida's mild, low-chill winters, the University of Florida's fruit breeding program developed several plums known as the Gulf series. All plums in this series begin with the prefix "Gulf" in their cultivar name. They are considered tropical plums suitable for Florida's USDA zones 8 through 9, with potential for use into USDA zone 10. These plums are better-suited to the central areas of the state, but show great promise for southern areas. Research on their performance in southwest Florida continues at the University of Florida Research & Education Center at Immokalee, Florida. For gardeners wishing to grow plums in the southwest region of the state, the Gulf series may be the only viable, commercially available choice for the region.

Plum Culture

• Like all fruit trees, plums should be planted in full sun and well-drained soil. Hilltop planting sites, where cold air will drain away to lower-lying areas, helps protect tender buds from freeze damage in spring. Although plums are not particular about soil requirements, optimal pH is between 5.5 and 6.5. Throughout Florida, irrigation will be necessary during the first year of the planting, with supplemental moisture during dry periods throughout the life of the tree. Most plums are not self-fruitful. This means another variety must be present for pollination to occur. Bruce plums and the Gulf series trees require pollinators, although the Gulf varieties are fruitful when crossed within the series. Heavy-fruiting trees, the Gulf series mature early, often bearing fruit in the second year after planting. Honey bees are the main pollinators for these and other Florida plums.