The only state where you'll find four-petal pawpaw, Asiminia tetramer, is Florida, and the only two counties in Florida where you'll find it are Martin and Palm Beach.
This plant is extremely rare. So rare that the number of living plants have been counted, numbered and regularly monitored. So rare that both the federal government and the state list four-petal pawpaw as endangered. The problem is that it exists only in the coastal sandpine ridges of the two counties, land that is also extremely rare these days in an undeveloped state. The only chance for the four-petal pawpaw's survival, really, is preservation of as much of this land as is practical.
Four-petal pawpaw is a member of the custard apple family (a more familiar and widespread member of the clan is the pondapple) and can grow to about 10 feet high. It has a tough, deep taproot that allows it to survive – and to an extent thrive after – intense fires. It actually produces more flowers and more fruit after a fire than in years prior, probably because open ground provides opportunity for new plants to establish themselves. It will survive when it's overshadowed by other plants, but it puts more energy into growing bigger leaves needed for photosynthesis and less into flowering and fruiting.
Four-petal pawpaw flowers as early as February, peaking in May and June, but continuing through the summer. The flowers are cream-colored on the outside and deep red at the center, which distinguishes it from its widespread cousin, netted pawpaw. They are also unpleasant smelling. The leaves grow alternately along the stem, are oblong in shape and fairly large. The fruit is a berry-like thing called a monocarpal: a single flower can produce as many as eight monocarpals and each monocarpal can have as many as nine seeds.
According to the U.S. Fish and Wildlife Service, beetles seem to be the major pollinators, although certain wasps and flies get into the act as well. The fruit, which is said to smell like a banana, ripens after two to three months; gopher tortoises and small mammals, including the Florida mouse, eat it and help distribute the seeds in the process. The seeds once planted take between one and eight months to germinate; the root system develops over the next several months before the stem and first leaves emerges. Four-petal pawpaw is a host to the zebra swallowtail butterfly.
A survey done by state in 1988 found there were 800 to 900 individual plants on 16 natural areas in Martin and Palm Beach. The Fish and Wildlife Service also noted that there were records saying that St. Lucie County was part of four-petal pawpaw's range but concluded that either was an error or the plant is now locally extinct.
Oddly enough, unlike many plants that seemingly were found, classified and named the moment the first Europeans stepped foot in Florida, the four-petal pawpaw wasn't discovered and categorized as a species until 1924. Even then, it was mistakenly considered part of different genus until 1960. It is a member of Annonacaeae, the custard apple family.