Euphorbia davidii |
Euphorbia falcata |
|
---|---|---|
David's poinsettia, David's spurge, tooth poinsettia, tooth spurge |
sickle spurge |
|
Habit | Herbs, annual, with taproot. | Herbs, annual, with taproot. |
Stems | erect or ascending, 20–70 cm, both coarsely and sparsely hirsute and closely strigillose; branches usually ± straight, occasionally proximal branches arcuate. |
erect, unbranched or branched, 5–20 cm, glabrous. |
Leaves | usually opposite, occasionally alternate at distal nodes; petiole 7–25 mm, strigose; blade usually narrowly to broadly elliptic, occasionally lance-elliptic, 10–100 × 5–35 mm, base cuneate to attenuate, margins coarsely crenate-dentate, strigose, revolute to nearly flat, apex broadly acute to acuminate, or obtuse, abaxial surface strigose with stiff, strongly tapered hairs, adaxial surface sparsely strigose-hirsute; venation pinnate, midvein prominent. |
petiole absent; blade obovate, linear-oblong, or spatulate, 2–20 × 2–10 mm, base cuneate or attenuate, margins entire, apex acute, obtuse, emarginate, or mucronate, surfaces glabrous; venation usually inconspicuous, sometimes 3-nerved from base, midvein prominent. |
Involucre | cylindric, 2.5–3 × 1.3–1.8 mm, glabrous; involucral lobes divided into 5–7 linear, papillate lobes; gland 1, yellow-green, sessile and broadly attached, 0.9 × 1.3 mm, opening oblong, glabrous; appendages absent. |
cupulate, 0.5–1.2 × 0.6–1.3 mm, glabrous; glands 4, elliptic to orbiculate, 0.2–0.3 × 0.3–0.8 mm; horns usually absent, occasionally divergent, 0.5–1.2 mm. |
Staminate flowers | 5–8. |
6–10. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 1 mm, 2-fid 1/2 to nearly entire length. |
ovary pilose only at base, styles 0.9–1.1 mm, 2-fid. |
Capsules | broadly ovoid, 2.9–3.3 × 4–4.8 mm, 3-lobed, glabrous; columella 2.2–2.7 mm. |
subovoid, 2–3 × 1.8–3 mm, slightly lobed; cocci rounded, smooth, glabrous or slightly pilose along abaxial region; columella 1.1–1.8 mm. |
Seeds | black to brown or pale gray, ovoid to triangular-ovoid, angular in cross section, 2.4–2.9 × 2.2–2.9 mm, low-tuberculate, tubercles irregularly arranged or in faint, transverse row; caruncle 0.9–1.1 mm. |
grayish, whitish, or light brownish, ovoid, 1.2–1.8 × 0.7–1.1 mm, transversally sulcate; caruncle subglobose to subconic, 0.2–0.5 × 0.2–0.5 mm. |
Cyathial | arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched; pleiochasial bracts 2–4, often whorled, green with diffuse greenish white to mauve near base, similar in shape and size to distal leaves or slightly narrower; dichasial bracts similar in shape to distal leaves but smaller, often highly reduced. |
arrangement: terminal pleiochasial branches 2–5, each 2–6 times 2-branched; pleiochasial bracts similar in shape to but usually shorter and wider than distal leaves; dichasial bracts distinct, widely ovate, rhombic, or suborbiculate, imbricate, base cordate, truncate or cuneate, margins finely denticulate, apex acute or obtuse, strongly mucronate; axillary cymose branches 0–10. |
Cyathia | peduncle 0.5–1 mm. |
peduncle 0–2 mm. |
2n | = 56. |
|
Euphorbia davidii |
Euphorbia falcata |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting spring–summer. |
Habitat | Forests, stream and riverbanks, prairies, roadsides and open disturbed areas. | Waste places, roadsides. |
Elevation | 200–1500 m. (700–4900 ft.) | 0–1600 m. (0–5200 ft.) |
Distribution |
AR; AZ; CA; CO; FL; IA; ID; IL; IN; KS; KY; LA; MA; MI; MN; MO; NC; NE; NJ; NM; NY; OH; OK; SD; TN; TX; UT; VA; VT; WI; WV; WY; ON; QC; Mexico (Chihuahua, Coahuila, Sonora) [Introduced in South America, Eurasia (China, Russia), Australia]
|
KY; MD; OH; PA; TN; VA; WV; s Europe; c Europe; w Asia; c Asia; s Asia; n Africa [Introduced in North America; introduced also in South America (Chile)] |
Discussion | Euphorbia davidii is native from the southwestern United States and northern Mexico north through the southern Great Plains; it apparently is adventive elsewhere. The species is the weediest member of the E. dentata species group (following M. H. Mayfield 1997) and has become an agricultural weed in North America, South America (for example, Argentina), and in the Old World (particularly Australia and Russia). Euphorbia davidii can be distinguished from the closely similar E. dentata by its larger capsules and seeds, often more elliptic leaves, and shorter, stiffer hairs. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 12, p. 320. | FNA vol. 12, p. 302. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | Tithymalus falcatus | |
Name authority | Subils: Kurtziana 17: 125, figs. 1, 2H–J. (1984) | Linnaeus: Sp. Pl. 1: 456. (1753) |
Web links |
|