2. Eryngium prostratum Nutt. (spreading eryngo)

Pl. 207 d, e; Map 858

Plants perennial, with thin, fibrous roots, glabrous, not glaucous. Stems 7–50 cm long, prostrate, creeping, rooting at the nodes. Leaves opposite or more commonly whorled and basal (rooted nodes may produce a new basal rosette with age), the blades entire or with a pair of narrow basal lobes, the venation netted. Basal leaves long-petiolate, the blades 1–4 cm long, lanceolate to broadly ovate, narrowed or rounded at the base, rounded to bluntly pointed at the tip, the margins entire or with few, relatively coarse, blunt teeth. Leaves at the nodes of the stems similar to the basal leaves, but sessile or mostly short-petiolate, the blades 0.4–2.5 cm long. Inflorescences more or less cylindrical heads 0.4–0.9 cm long, axillary, solitary, mostly long-stalked, grayish blue. Bracts subtending each head 5–10, 2–12 mm long, linear to narrowly lanceolate or narrowly oblanceolate, sharply pointed at the tip, the margins entire or with a few minute teeth. Terminal bracts absent. Flowers numerous, sessile, each subtended by a narrowly lanceolate bractlet 0.5–0.8 mm long. Sepals 0.5–0.8 mm long, ovate to broadly ovate, entire, usually with broad, thin, pale margins. Petals obovate, rounded or shallowly notched at the tip, blue or less commonly white. Ovaries with minute, white tubercles. Fruits 0.5–0.8 mm long, broadly oblong-obovate in outline, with minute, white tubercles. 2n=16. May–November.

Scattered in the southeastern quarter of the state (southeastern U.S. west to Missouri and Texas). Swamps, bottomland forests, margins of ponds, sinkhole ponds, and lakes, banks of streams and rivers, and fens; also pastures.

This diminutive creeping species was recorded by Steyermark (1963) from moist to wet habitats in the Mississippi Lowlands Division and margins of scattered sinkhole ponds in the eastern half of the Ozarks. In more recent years, however, it appears to have spread to a number of additional wetland communities within the original range and is probably more abundant now than it was prior to the 1960s.