PORTULACACEAE (purslane family)

Plants annual or perennial herbs (woody elsewhere), often somewhat succulent, sometimes with tubers or with thickened or tuberous roots. Aerial stems simple or branched, sometimes reduced and inconspicuous (absent elsewhere), erect to spreading. Leaves basal and/or alternate or opposite, the leaves at each node equal in size or nearly so, sessile or petiolate. Stipules absent or uncommonly represented by hairs at the nodes (in Portulaca). Leaf blades simple, variously shaped, the margins usually entire. Inflorescences terminal and/or axillary clusters, racemes, or panicles, sometimes appearing umbellate, occasionally reduced to a solitary flower, the flowers and/or branch points sometimes associated with leaflike or scalelike bracts. Flowers actinomorphic, perfect, hypogynous or (in Portulaca) perigynous to epigynous. Calyces of 2 free sepals (3–9 elsewhere), these sometimes overlapping basally, persistent at fruiting or shed as the flower opens. Corollas of 4–6 free petals (rarely numerous in doubled horticultural forms, occasionally fused basally elsewhere, occasionally shed as the flower opens and thus appearing apetalous elsewhere), these variously shaped, sometimes rounded or shallowly notched at the tip.Stamens 4 to numerous, often appearing opposite the petals, the filaments distinct or fused basally into clusters, sometimes attached to the petal bases, the anthers small, various colors, dehiscing longitudinally. Staminodes absent.Pistil 1 per flower, the ovary superior or (in Portulaca) partially to completely inferior, of usually 3 fused carpels, with 1 locule, the placentation free central or basal. Style 1, 3–9-branched nearly to the base or nearly unbranched, the stigmas 1 per style branch (sometuimes appearing as a single, lobed unit when the styles are fused to near the tip), capitate, club-shaped, or linear. Fruitscapsules, 1 to many-seeded, the dehiscence longitudinal or circumscissile, sometimes only with age. Seeds kidney-shaped to globose, sometimes somewhat flattened, the embryo appearing curved or coiled. Twenty to 30 genera, about 450 species, worldwide.

The family is treated here in the traditional sense, as the familial limits are still controversial. Several phylogenetic studies based on both morphological and molecular markers have provided evidence that, on the one hand, such families as Basellaceae, Cactaceae, and Didiereaceae are specialized derivatives from within the Portulacaceae as traditionally circumscribed, and on the other hand that there exist three or more major lineages within the traditional Portulacaceae that could be classified as separate families (Rodman, 1990, 1994; Hershkovitz and Zimmer, 1997; Applequist and Wallace, 2001; Edwards et al., 2005; Nyffeler, 2007; Nyffeler and Eggli, 2010). By this latter view, among the genera in Missouri only Portulaca would be retained in Portulacaceae in the strict sense; Claytonia and Phemeranthus would be classified in the Montiaceae and Talinum would be segregated into the Talinaceae.

A number of members of the Portulaceae are cultivated as garden ornamentals, including various species of Lewisia Pursh, Phemeranthus, Portulaca, and Talinum. A few of the larger succulents are grown as specimen plants in homes, greenhouses, and conservatories.