2. Euphorbia corollata L. (flowering spurge)

Agaloma corollata (L.) Raf.

Tithymalopsis corollata (L.) Klotzsch & Garcke

E. corollata var. mollis Millsp., misapplied

E. corollata var. paniculata (Elliott) Boiss., misapplied

Map 1664, Pl. 379 a, b

Plants perennial herbs, with a deep, spreading, usually branched rootstock. Stems 20–100 cm long, erect or ascending, unbranched below the inflorescence or occasionally few-branched, the branches not flattened toward the tip, green to yellowish green or tan, rarely reddish- or purplish-tinged, glabrous or less commonly sparsely to moderately pubescent with slender, mostly spreading hairs. Leaves alternate below the inflorescence branches (those of the inflorescence branches alternate, opposite, or whorled) not appearing crowded, sessile or rarely minutely petiolate. Stipules absent or a pair of minute, light brown, convex to conical, sessile glands. Leaf blades 10–60 mm long, unlobed, the margins entire, the surfaces glabrous or sparsely to moderately pubescent with slender, mostly spreading hairs, green to bright green; those below the inflorescence narrowly lanceolate to more commonly oblong, oblong-oblanceolate or elliptic, mostly tapered at the base, rounded or short-tapered to a sharply pointed tip; those along the inflorescence branches narrowly elliptic to elliptic or narrowly ovate (much longer than wide), rounded or angled at the base, angled to a bluntly or sharply pointed tip. Inflorescences terminal umbellate panicles with a whorl of leaves at the base and each of the 3–6(–10) primary branches usually branched 3–5 additional times, the cyathia solitary at the branch tips and branch points. Involucre 1.2–1.8 mm long, glabrous or the outer surface minutely and inconspicuously hairy toward the rim, the rim shallowly 5-lobed, the margin minutely fringed or hairy, the marginal glands 5, 0.5–1.0 mm long, narrowly elliptic to nearly linear, yellowish green to green, with a relatively conspicuous petaloid appendage 1.5–4.5 mm long, this white. Staminate flowers 10–21 per cyathium. Ovaries glabrous, the styles 0.7–1.0 mm long, each divided 1/3–1/2 of the way from the tip into 2 relatively stout lobes, these sometimes somewhat club-shaped. Fruits 2.5–4.5 mm long, glabrous. Seeds 2.5–2.8 mm long, oblong-elliptic to broadly ovate in outline, nearly circular in cross-section, rounded or somewhat angled at the base, the surface smooth or with shallow, faint pits, purplish brown but usually with a thin, white coating, lacking a caruncle. 2n=26, 28, 30. May–October.

Scattered to common throughout the state (eastern U.S. west to South Dakota and Texas; Canada). Upland prairies, glades, ledges and tops of bluffs, savannas, openings of mesic to dry upland forests, and banks of streams and rivers; also pastures, old fields, fallow fields, fencerows, railroads, roadsides, and rarely open, disturbed areas.

More so than in any of the other species of Euphorbia in Missouri, in this attractive species the cyathia with their showy appendages resemble individual normal flowers, and the true nature of the cyathium is apparent only with close observation. Steyermark (1963) treated E. corollata as comprising three varieties differing in stem and leaf pubescence and cyathium size and density. However, the names that he used, var. mollis Millsp. and var. paniculata (Elliott) Boiss., technically are associated with a different species, the southeastern E. pubentissima Michx., which occurs no closer to Missouri than central Tennessee and northern Louisiana. That species differs from E. corollata in its shorter, more slender stems, usually downward-angled, mostly short-petiolate leaves, and involucral glands with somewhat smaller, oval to nearly circular petaloid appendages. Both Huft (1979) and Park (1998) included the epithets var. mollis and var. paniculata as synonyms of E. pubentissima, and both of these monographers of the group treated E. corollata and E. pubentissima as inherently variable species in which formal taxonomic recognition of varieties was not advisable.