A small (1-4 cm tall), ephemeral, succulent winter annual that usually completes its life cycle within a 4-week period in the spring. Young plants are grayish; mature plants reddish-purple. Flowers are inconspicuous. This unusual species comprises the monotypic genus Geocarpon.
Glabrous winter annual, stems simple or branched at the base, the branches few, erect or spreading ascending, mostly 3-4 cm high and less than 0.5 mm thick, often a bright pinkish or reddish or pale purplish color. Leaves simple, opposite, green or pinkish in color, 3-4 mm long, narrowly oblong or ovate-oblong, the margins entire, and the apex acute. Flowers usually axillary, regular, funnelform-campanulate; sepals 5, 3-4 mm long, reddish or reddish-green; petals absent; stamens 5; staminodes 5; ovary superior, lance-ovoid, somewhat trigonous, about the length of the sepals. Fruit is a capsule containing numerous, long-funicular seeds.
In Texas, Geocarpon minimum occurs in a saline barren complex at the vegetative (micro-flora) edge of saline 'slicks' (barren spots), just above the floodplain of the Neches River. The vegetative edge is sometimes called a cryptogrammic lip,' referring to the lichen species and Nostoc sp. that concentrate at the edge of the slicks and the lack of competition with the micro-flora at the vegetative edge of the slicks. The local soils are not mapped at this level of detail but appear to be clay pans, holding late winter rains with a spongy feel to the soil and drying off quickly into a hard cement. The topography also includes mima mounds with micro highs and lows. The site is dominated by micro flora. The saline slick barrens are primarily devoid of vegetation.
Found in southwestern Missouri (Dade, Polk, Greene, and Lawrence Counties). Historically found in St. Clair & Jasper Counties, Missouri. Found in three southeastern counties in Arkansas (Cleveland, Drew, and Bradley) and one northwestern County (Franklin). Also found at two locations in Louisiana (Wynn Parish). In early 2004, confirmed in northeast Texas (Anderson County).
Threats and Reasons for Decline
A major threat to Geocarpon is the destruction or adverse modification of its habitat. In Missouri, some sites have been damaged by trampling and grazing by cattle. It has been suggested that physical disturbance may actually benefit Geocarpon at some sites by maintaining bare substrate for seedling establishment. A more serious threat is from pasture improvement with the subsequent invasion by prairie species. ORVs have also damaged Geocarpon habitat. In southern Arkansas much of the habitat suitable for Geocarpon has been heavily disturbed by silviculture, pasture, agriculture, and road expansion.
Flowering: Late February through March. Illustrations: Line drawings appear in Steyermark (1963). A black-and-white photograph is provided in Steyermark, Voigt & Mohlenbrock (1959). In March 2004, a color photograph appeared on the website of the Center for Plant Conservation.