Distribution: Scrub plum occurs on the Lake Wales Ridge in Lake, Osceola, Orange, Polk and Highlands Counties, Florida.

Habitats: Scrub plum occurs on both white and yellow sands in sandhill and scrub habitats.

Life History: Scrub plum is a long-lived, multi-stemmed (but non-clonal) woody shrub to 1.5m in height. It has the spiny ziz-zag branching and small, dry season-deciduous leaves characteristic of many plants adapted to xeric habitats. The five-petaled flowers are about 1 cm in diameter and have numerous stamens with conspicuous yellow anthers that are exerted well above the floral cup. Some flowers have a well-developed pistil equal in height to the stamens, while in other flower the pistil is vestigial and nonfunctional. Fruits are 1 to 2.5 cm long ovoid drupes that take on a vaguely peachy color as they ripen.

Phenology: Plants typically add stems annually, especially in recently burned populations. Individuals drop most of their leaves in the winter dry season. Flowering occurs in February-March when the plants are largely leafless. Long-unburned individuals flower sparsely or not at all. Fruit maturation is low in comparison to flowering due to high levels of premature abscission and predation.

Breeding System and Pollination: Scrub plum is andromonoecious. Andromonoecy is a rare breeding system characterized by the presence of male and bisexual flowers on the same individual. The fragrant white flowers attract numerous insect visitors. Scrub plum is believed to be self-incompatible.

Genetics: There have been no studies of scrub plum genetics.

Population Dynamics: Seedling recruitment appears to be rare in scrub plum. Adult mortality is very low. Scrub plum resprouts vigorously following fire, but flowering declines with time-since-fire. Long-unburned populations seem to persist with little change in size for many years.

Interesting Facts: Andromonoecy is found in only 2% of flowering plants. It is thought to be an adaptation that optimizes allocation of resources to male and female function. Under this hypothesis, natural selection favors the termination of investment in female function (and female structures) once female reproductive success is maximized, but individual fitness may be enhanced by continued investment in male function since male flowers entail lower costs (e.g., no cost of fruit and seed production). Male flowers may enhance overall plant fitness in at least two ways. By adding to floral display, they may attract additional pollinators and they may contribute pollen to fertilizations on other plants in the population.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: The Plant Ecology Lab has been studying scrub plum since 1996. We have conducted demographic monitoring of tagged individuals in several populations at Lake Wales Ridge State Forest and at Lake Wales Ridge National Wildlife Refuge (Carter Creek Sandhill). Recent burns are allowing us to assess whether fire intensity affects demography. Currently we are investigating the reproductive biology of scrub plum by conducting experiments to document the details of its unusual breeding system and by monitoring fruit development. We are also carrying out germination experiments.

Data Availability: No are data available at the present time.

Contact Person: Carl W. Weekley

Literature Cited:

1. Bertin, R.I. 1982. The evolution and maintenance of andromonoecy. Evolutionary Theory 6:25-32.
2. U.S. Fish and Wildlife Service. 1999. Scrub plum. South Florida multi-species recovery plan. U.S. Fish and Wildlife Service, Atlanta, Georgia, USA.
3. Weekley, C.W. 1997. Prunus geniculata monitoring report. Unpublished report to the Florida Plant Conservation Program of the Division of Forestry, Tallahassee, FL, 5+ pp.
4. Willson, M.F. 1983. Plant reproductive biology. John Wiley & Sons, NY.

Home | Top | Index