Euphorbia spathulata
Euphorbia graminea
prairie spurge, reticulate seed spurge, spatulate leaf spurge, warty spurge
grassleaf spurge
erect or ascending, unbranched or branched, 10–70 cm, glabrous.
erect or ascending, branched, 30–80(–110) cm, strigillose or glabrescent, sharply angled.
petiole absent or to 0.2 mm;
blade oblanceolate, oblong-oblanceolate, spatulate, or cuneate, 10–50 × 6–11 mm, base broadly attenuate to rounded or shallowly cordate-clasping, margins finely serrulate (usually distally), apex usually rounded to obtuse, occasionally slightly retuse or obcordate proximally, bluntly mucronate, surfaces glabrous;
venation pinnate, midvein prominent.
usually alternate, sometimes some opposite;
stipules usually 0.2–0.5 mm, rarely rudimentary;
petiole 0.4–5.9 mm, strigillose;
blade ovate, elliptic, linear-elliptic, or oblong, 10–83 × 3–39 mm, base attenuate, rounded, or cuneate, margins entire, apex acute or obtuse, surfaces strigillose;
venation occasionally obscure on narrow leaves, midvein conspicuous.
campanulate to cupulate, 0.6–1(–1.5) × 0.8–1.2 mm, glabrous;
glands 4–5, elliptic, oblong, to slightly reniform, 0.2–0.6 × 0.4–1 mm;
horns absent.
campanulate or obconic, 1–1.8 × 0.8–1.7 mm, glabrous or strigillose toward rim;
glands (1–)2–4, yellow to greenish, elliptic or oblong, 0.1–0.3 × 0.2–0.4 mm;
appendages white to tinged purple, ovate and often hoodlike or forming narrow rim around distal margin of gland, 0.3–1.6 × 0.4–0.9 mm, entire.
3–10.
30–40.
ovary glabrous;
styles 0.8–1.5 mm, 2-fid.
ovary glabrous;
styles 0.7–1 mm, 2-fid from 1/2 to nearly entire length.
depressed-globose, 2–3.5 × 4 mm, 3-lobed;
cocci rounded, verrucose, verrucae 0.1–0.2 mm, glabrous;
columella 1.4–2.2 mm.
ovoid-oblate, 2.5–3 × 3–3.5 mm, glabrous;
columella 1.6–1.9 mm.
red-brown to dark purple, occasionally ± glaucous, broadly ellipsoid-ovoid to nearly globose, 1.3–2.5 × 1.5–1.8 mm, smooth, reticulate, or finely low-ridged;
caruncle irregularly reniform to round, subconic to lenticular, 0.3–0.4 × 0.5–0.6 mm.
gray, brown, or nearly black, ovoid, circular or weakly angled in cross section, 1.5–1.7 × 1.3–1.5 mm, coarsely tuberculate with longitudinal rows of shallow pits;
caruncle absent or punctiform, 0.1–0.2 mm.
arrangement: terminal pleiochasial branches 3(–5), each 1–3 times 2-branched;
pleiochasial bracts broadly ovate to ovate-oblong, shorter and wider than distal leaves;
dichasial bracts distinct, broadly ovate, ovate-triangular, or ovate-elliptic, base cordate-clasping or subcordate to rounded, margins serrulate, apex rounded to obtuse or acute;
axillary cymose branches (0–4)5–12.
peduncle 0.3–1(–1.5) mm.
in usually terminal, rarely axillary, dichasia, distal dichasial bracts often white;
peduncle 0.4–4.5 mm (to 15 mm at first node of inflorescence), glabrous.
Euphorbia spathulata
Euphorbia graminea
As treated here, Euphorbia spathulata is a wide-ranging and variable species. J. B. S. Norton (1900) recognized a number of segregates (for example, E. arkansana, E. dictyosperma, and E. obtusata) all of which are included here in a broadly defined E. spathulata. The only segregate species that has been widely recognized in regional floras is E. obtusata (for example, M. L. Fernald 1950; T. S. Cooperrider 1995; G. Yatskievych 1999–2013, vol. 2). Authors have generally distinguished the eastern North American E. obtusata from the western E. spathulata by the former's larger seeds (1.7–2.3 mm versus 1.5–1.7 mm) with smooth (versus reticulate) surfaces, larger involucres, red (versus yellow) involucral glands, and cordate-clasping (versus rounded to subcordate) dichasial bracts. Examination of specimens of E. spathulata in the broad sense from throughout North America showed that there is some geographic patterning to seed size and surface sculpturing, but the variation does not segregate cleanly into two discrete taxa. Plants from western North America typically have small seeds (1.5–1.7 mm) with reticulate surfaces, although some western individuals have seeds 1.8–1.9 mm long with reticulate surfaces. Plants from Texas generally have small seeds (1.5–1.6 mm) but with the surfaces either reticulate or completely smooth. Plants from adjacent Louisiana have small seeds with faintly reticulate to almost bumpy surfaces. Plants from eastern North America have larger seeds (2–2.3 mm) with usually smooth surfaces, although individuals from Tennessee and the Carolinas have faintly reticulate surfaces. Involucre height, gland color, and the shape of the dichasial bracts do not segregate with seed size as previous treatments have suggested.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Euphorbia graminea occurs natively from northern South America to northern Mexico. The species is a variable and taxonomically complex entity whose boundaries are not well defined and are in need of further study. Euphorbia graminea is often weedy and has recently become established in warmer areas of the southern United States, where it will likely become more common in the future. In recent years, a cultivar of E. graminea has found considerable horticultural success and is marketed under the trade name "Diamond Frost."
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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