Euphorbia davidii |
Euphorbia pubentissima |
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David's poinsettia, David's spurge, tooth poinsettia, tooth spurge |
false flowering spurge, southeastern flowering spurge |
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Habit | Herbs, annual, with taproot. | Herbs, perennial, with spreading rootstock. |
Stems | erect or ascending, 20–70 cm, both coarsely and sparsely hirsute and closely strigillose; branches usually ± straight, occasionally proximal branches arcuate. |
erect, usually unbranched, occasionally few branched distally, solitary or few, previous year's dead stems not persistent, 30–65 cm, usually glabrous, rarely villous. |
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. |
alternate; stipules 1 mm; petiole (0–)1–2(–10) mm, glabrous or densely villous; blade lanceolate, lance-ovate, elliptic, or obovate, 40–68 × 6–18 mm, often reflexed, base cuneate to rounded, margins entire, apex usually rounded, sometimes broadly acute, abaxial surface glabrous or villous, adaxial surface usually glabrous, rarely sparsely villous; venation occasionally obscure on small leaves, midvein conspicuous. |
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. |
campanulate or hemispheric, 1.3–1.7 × 1.8–2.2 mm, glabrous or villous; glands 5 (7–10 on central cyathium), green, reniform or broadly elliptic, 0.3–0.5 × 0.5–0.8 mm; appendages white, orbiculate or narrowly flabellate, 1–2.2 × 1.5 mm, entire. |
Staminate flowers | 5–8. |
20–25. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 1 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous or sparsely villous; styles 0.6–1.1 mm, 2-fid 1/2 length. |
Capsules | broadly ovoid, 2.9–3.3 × 4–4.8 mm, 3-lobed, glabrous; columella 2.2–2.7 mm. |
globose, 2–2.4 × 3.3–4.8 mm, glabrous or sparsely villous; columella 1.8–2.1 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. |
light gray, ovoid, 2.2–2.4 × 1.6–1.8 mm, with shallow depressions; caruncle absent. |
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. |
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Cyathia | peduncle 0.5–1 mm. |
in terminal pleiochasia; peduncle 1–5 mm (or 15–40 mm on early flowering individuals), usually glabrous, occasionally sparsely villous. |
2n | = 56. |
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Euphorbia davidii |
Euphorbia pubentissima |
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Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting spring–fall. |
Habitat | Forests, stream and riverbanks, prairies, roadsides and open disturbed areas. | Open fields, cliffs, woods, floodplains. |
Elevation | 200–1500 m. (700–4900 ft.) | 0–900 m. (0–3000 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]
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AL; FL; GA; LA; MD; MS; NC; SC; TN; VA; WV
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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.) |
The taxonomic history of Euphorbia pubentissima is complex. The species has been included within a very broadly defined E. corollata in the past. Therefore, its geographic distribution appears significantly more wide-ranging in some treatments. The framework established by M. J. Huft (1979) and later by K. R. Park (1998) is followed here. Euphorbia pubentissima is recognized as a variable species restricted to the southeastern United States. The species can be distinguished from E. corollata by its shorter involucral gland appendages and smaller seeds. Euphorbia paniculata Elliott, which sometimes is applied to E. pubentissima, is an illegitimate name (a later homonym of Euphorbia paniculata Desfontaines). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 320. | FNA vol. 12, p. 250. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Synonyms | E. apocynifolia, E. corollata var. paniculata, E. corollata var. zinniiflora, E. zinniiflora, Tithymalopsis apocynifolia, T. paniculata, T. zinniiflora | |
Name authority | Subils: Kurtziana 17: 125, figs. 1, 2H–J. (1984) | Michaux: Fl. Bor.-Amer. 2: 212. (1803) |
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