Four-petal Pawpaw

Asimina tetramera

Description

Four-petal pawpaw, Asimina tetramera, is a large woody shrub, formed of one or several upright stems, 3.3-10 ft (1-3 m) tall, with large toothless leaves. Flowers have four sepals and six pink or maroon petals (two sets of three each); fruits are pale yellow. Flowering occurs primarily from May to August and sporadically in other months. The fruiting period is from about May to September. The flowers give off a fetid odor.

Habitat

Four-petal pawpaw's habitat is the sand pine scrub that grows along old dune ridges. The plant is well-adapted to the occasional severe fires and hurricanes that visit its habitat, because new sprouts grow readily from the roots. Without fire and hurricanes, four-petal pawpaw is eventually shaded out by evergreen oaks and sand pines.

Distribution

The plant was first discovered in 1924 at Rio, Florida, just north of Stuart. Historically, four-petaled pawpaw grew throughout the scrub sand pine dunes along the Atlantic coast of Florida, stretching from the coast inland in Martin and northern Palm Beach counties.

Much of the original pine scrub habitat of four-petal pawpaw has undergone urban development, and the species is now restricted to small remnant patches of scrub throughout its range. About 100 plants grow in Jonathan Dickinson State Park. In 1985, several dozen plants were surveyed in the Hobe Sound National Wildlife Refuge. Sixty plants grow on several acres that serve as a biological preserve on the grounds of an office building in Palm Beach County.

Other remaining four-petal pawpaw plants are mostly on private lands, scattered along U.S. Highway 1 in northern Palm Beach County, where urban development is proceeding at a break-neck pace. Already one-third of about 100 plants surveyed in June 1985 in Palm Beach and Martin counties outside of parks or preserves have been lost to residential development. Estimated population numbers in the primary sites are: Jonathan Dickinson State Park -100; private grounds of an office building in Palm Beach County -60; and a Palm Beach County park -40. A total of about 500 plants are known to exist in the wild

Threats

Where scrub vegetation survives, four-petal pawpaw may die out because brush fires have been controlled. When there is no fire, scrub oaks or sand pines eventually overtop and shade out the pawpaw. Both Jonathan Dickinson State Park and Hobe Sound National Wildlife Refuge have a program for prescribed burning of vegetation. Tracts of scrub on private land may have to be renewed by other methods, such as cutting. Most of the original sand pine scrub habitat is now urbanized, and the species is essentially confined to remnant areas of scrub vegetation in scattered sites.

Conservation and Recovery

The prescribed fire management plan at the Hobe Sound National Wildlife Refuge should help these plants survive there, but there is little hope for plants on private land, unless landowners can be convinced of the value of preserving sand pine scrub habitat.

The plant is protected in Jonathan Dickinson State Park except for small areas that are used for military communication facilities, which could be altered in the future. Four-petal pawpaw may also occur in areas on or near the Hobe Sound National Wildlife Refuge where the U. S. Army Corps of Engineers holds easements for disposal of dredge spoils from the Intracoastal Waterway. The plants which occur in a Palm Beach County park are threatened by the development of recreational facilities and by illegal dumping.

While resprouting from the roots is characteristic of the species, reproduction from seeds appears to be limited. The large seeds of four-petal pawpaw have oily endosperm and apparently a limited period of viability. Seed collected from fresh, ripe, fruit planted immediately germinated well, but older seeds did not germinate. Cultivated seedlings, grown for four years, have grown slowly, with most growth concentrated in the root system which is sensitive to transplanting disturbance. This indicates that the shrub has a limited reproductive capacity, that long-term germplasm storage may be impractical, and it appears that this shrub's reproductive capacity in the wild is very limited. The species is also so limited in distribution and population size that any indiscriminate scientific or other collecting would pose a threat to its existence. Florida law does regulate taking, transport, and sale of the plants, but it does not provide habitat protection. Moyroud and Susan Wallace of Bok Tower Gardens have successfully germinated seeds and grown young plants in a garden setting.

Contacts

Regional Office of Endangered Species
U. S. Fish and Wildlife Service
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

Jacksonville Ecological Services Field Office
6620 Southpoint Dr. S., Suite 310
Jacksonville, Florida 32216-0958
Telephone: (904 )232-2580
Fax: (904) 232-2404

References

Austin, D.F., and B.E. Tatje. 1979. Asimina tetramera, pp. 5-6. In D.B. Ward, ed. Rare and Endangered Biota of Florida; Vol. 5, Plants. University Presses of Florida, Gainesville.

Austin, D. F., B. E. Tatje, and C. E. Nauman. 1980"Status Report on Asimina tetramera." U.S. Fish and Wildlife Service, Atlanta.

Kral, R. 1983. "Asimina tetramera." In Report onSome Rare, Threatened, or Endangered Forest-Related Vascular Plants of the South. U.S. Department of Agriculture Forest Service, Washington, D.C.

U.S. Fish and Wildlife Service. 1988. Recovery Plan for Three Florida Pawpaws. U.S. Fish and Wildlife Service, Atlanta, Georgia. 20 pp.

U.S. Fish and Wildlife Service. 1986. Endangered and Threatened Wildlife and Plants: Endangered Status for Three Florida Shrubs. Federal Register 51(187):34415-34420.

Wilbur, R. 1970. "Taxonomic and Nomenclatural Observations on the Eastern North American Genus Asimina (Annonaceae)." Journal of the Elisha Mitchell Scientific Society 86:88-95.

Wunderlin, R. P., D. Richardson, and B. Hansen.1980. "Status Report on Asimina rugelii." Report.U.S. Fish and Wildlife Service, Atlanta.