Euphorbia dentata |
Euphorbia bifurcata |
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green poinsettia, tooth poinsettia, tooth spurge |
fork spurge |
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Habit | Herbs, annual, with taproot. | Herbs, annual, with slender, fibrous taproot. |
Stems | erect or ascending, 15–60 cm, both pilose and inconspicuously strigillose; branches usually ± straight, occasionally proximal branches arcuate. |
erect, 20–70 cm, glabrous or with few scattered spreading hairs; branches arcuate, branching appearing dichotomous. |
Leaves | usually opposite, occasionally alternate at distal nodes; petiole 5–20 mm, pilose; blade 30–70 × 4–35 mm, narrowly lanceolate to suborbiculate, usually broadest below middle, base usually acute to subobtuse, rarely subtruncate, margins coarsely crenate-dentate or doubly crenate, strigillose, flat to slightly revolute, apex broadly acute, abaxial surface long pilose with weak, filiform hairs, adaxial surface sparsely pilose to glabrate; venation pinnate, midvein prominent. |
usually alternate, occasionally opposite at proximalmost node; petiole 15–49 mm, glabrous; blade usually ovate, rarely oblong or elliptic, 13–54 × 7–38 mm, base usually rounded to broadly cuneate, rarely truncate, margins finely serrulate, apex obtuse, surfaces glabrous or with few scattered hairs; venation pinnate, midvein prominent. |
Involucre | campanulate, 3.8 × 1.8 mm, glabrous; involucral lobes divided into several linear, smooth lobes; glands (1–)2, green, sessile and broadly attached, 0.7–0.9 × 0.9–1.2 mm, opening oblong, glabrous; appendages absent. |
tubular or obconic, 1–1.7 × 0.7–1.4 mm, glabrous except for few hairs on lobes; involucral lobes divided into several linear, smooth lobes; glands 1(–3), greenish, sessile and broadly attached, 0.3–0.4 × 0.4–0.8 mm, opening oblong to subcircular, glabrous; appendages petaloid, white, elliptic, oblong, transversely oblong, or forming thin, lunate rim on gland margin, not incurved and covering glands, 0.3–0.9 × 0.6–1.3 mm, entire, undulate or slightly lobed, glabrous. |
Staminate flowers | 8–10. |
20–30. |
Pistillate flowers | ovary glabrous, styles 1.2 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous; styles 0.6–1 mm, 2-fid 1/2 length. |
Capsules | depressed-globose, 2.5–2.8 × 3.5–4 mm, 3-lobed, glabrous; columella 1.8–2.1 mm. |
oblate, 2.8–3.1 × 3.6–4.5 mm, glabrous; columella 1.9–2.4 mm. |
Seeds | pale gray to black, ovoid, rounded in cross section, 2.1–2.7 × 1.7–2.1 mm, evenly minute-tuberculate; caruncle 0.4–0.6 mm. |
brown to blackish, ovoid, rounded in cross section, 1.9–2.4 × 1.5–1.8 mm, irregularly and coarsely tuberculate; caruncle absent or rudimentary. |
Cyathial | arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched; pleiochasial bracts 2–4, often whorled, wholly green or paler green, white, or mauve at 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 dichasial branches 2, few-branched (weakly defined); pleiochasial bracts 2–3, opposite or whorled, wholly green, similar in shape and size to distal leaves; dichasial bracts smaller than distal leaves, often white at base. |
Cyathia | peduncle 0.7–1 mm. |
peduncle 0.9–3.5(–6.2) mm. |
2n | = 28. |
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Euphorbia dentata |
Euphorbia bifurcata |
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Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting summer–fall. |
Habitat | Bottomland forests, stream and river banks, bluffs, prairies, glades, fallow fields, roadsides, railroad cinders, open disturbed areas. | Riparian areas with cottonwoods and willows, pinyon pine woodlands, pine-oak forests, Douglas fir forests with pines. |
Elevation | 0–1000 m. (0–3300 ft.) | 1900–2300 m. (6200–7500 ft.) |
Distribution |
AL; AR; GA; IA; IL; IN; KS; KY; LA; MD; MI; MO; MS; NC; NE; OH; OK; PA; SC; TN; TX; VA; WV; ON; Mexico (Chihuahua, Coahuila, Nuevo León, Tamaulipas)
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NM; TX; Mexico; Central America (Guatemala) |
Discussion | Euphorbia dentata is native from northern Mexico and the south central United States north and east through the Ohio River Valley. Scattered occurrences in the southeastern United States likely represent adventive populations. Reports of E. dentata as a noxious weed (from the United States and the Old World) should most likely be attributed to introductions of E. davidii. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia bifurcata is found in the mountains of southern New Mexico (Doña Ana, Grant, Lincoln, Otero, and Sierra counties) and trans-Pecos Texas (Brewster, Jeff Davis, and Presidio counties). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 321. | FNA vol. 12, p. 319. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > sect. Poinsettia |
Sibling taxa | ||
Synonyms | Poinsettia dentata | |
Name authority | Michaux: Fl. Bor.-Amer. 2: 211. (1803) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 190. (1859) |
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