Plants annual; roots fleshy. Stems erect or suberect, fleshy, succulent; trichomes inconspicuous at nodes and in inflorescence; branches 5-35 cm. Leaf blades linear to lanceolate, terete to hemispheric, 5-15 × 1-3(-5) mm, apex acute; involucrelike leaves (3-)5-8. Flowers 9-15 mm diam.; petals yellow, obovate to oval-obovate, 5-8 × 2-5 mm, apex rounded; stamens 12-30; stigmas 5-7. Capsules subglobose, 3.3-5.5 mm diam. Seeds brownish red, dark brown, or rarely black, orbiculate or elongate, flattened, 0.6-0.65 mm; surface cells slightly raised, obscurely stellate, sometimes granular, tubercles absent. 2n = 16.

Flowering year-round. Coastal beaches and shell mounds; 0 m; Fla.; West Indies; South America.

Portulaca rubricaulis traditionally has been treated as P. phaeosperma (J. K. Small 1933). C. D. Legrand (1962) and R. P. Wunderlin (1982) consider the types of P. phaeosperma and P. rubricaulis to be conspecific. Only the yellow-flowered form has been seen in the United States; Legrand reported a salmon or orange-red to red form from the Caribbean.