Euphorbia heterophylla |
Euphorbia sect. Poinsettia |
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Mexican fireplant, painted euphorbia |
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Habit | Herbs, annual, with taproot. | Herbs, annual or perennial [rarely shrubs or small trees], with taproot or tuberous rootstock. | ||||||||||||||||||||||||||||||||||||
Stems | erect-ascending, 20–100 cm, sparsely pilose to villous; branches ± straight. |
erect or ascending, branched, terete, glabrous or hairy. |
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Leaves | usually alternate, occasionally opposite proximally; petiole 10–50 mm, pilose; blade narrowly lanceolate to elliptic or broadly obovate (then usually pandurate and 4-lobed), often polymorphic on single plants, 30–200 × 20–140 mm, base acute, margins sparsely glandular-serrulate, hirtellous, flat, apex acute to obtuse, abaxial surface sparsely appressed-pilose, adaxial surface sparsely pilosulous to glabrate; venation pinnate, midvein prominent. |
opposite or alternate; stipules usually present, occasionally absent, at base of petiole; petiole present, glabrous or hairy; blade monomorphic (occasionally polymorphic in E. cyathophora and E. heterophylla), base symmetric, margins entire or toothed, flat to revolute, surfaces glabrous or variously hairy; venation pinnate, midvein often prominent. |
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Involucre | usually campanulate, occasionally nearly hemispheric, 1.5–1.9 × 1.2–1.8 mm, glabrous; involucral lobes divided into several linear, smooth lobes; gland 1, yellow-green, stipitate, clavate, 1–1.4 × 1–1.2 mm, opening circular (occasionally flattened from pressing), with annular rim, glabrous; appendages absent. |
± actinomorphic, not spurred; glands 1–3 (sometimes 4–5 in E. eriantha, E. exstipulata, and E. radians), sessile or stipitate, shallowly cupped to deeply concave; appendages absent or petaloid (E. bifurcata, E. eriantha, and E. exstipulata). |
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Staminate flowers | 8–15. |
3–25. |
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Pistillate flowers | ovary glabrous or puberulent; styles 0.8–1.3 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous or hairy; styles distinct, occasionally appearing connate at base, unbranched or 2-fid. |
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Capsules | broadly ovoid, 2.8–3.8 × 4–5.3 mm, 3-lobed, usually glabrous, rarely sparsely puberulent; columella 2.1–2.8 mm. |
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Seeds | brown-gray to ashy gray, broadly deltoid, 2.4–2.8 × 1.9–2.4 mm, angular in cross section, dorsal face strongly acute-carinate, tuberculate, with broad rounded tubercles in 2 rows; caruncle 0.1 mm. |
caruncle present or absent. |
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Cyathial | arrangement: terminal dichasial branches usually 2, occasionally reduced to congested cyme, 1–2-branched (often congested and difficult to discern); pleiochasial bracts 2–4, often whorled, wholly green or paler green at base, similar in shape and size to distal leaves; dichasial bracts highly reduced, rarely absent in highly congested clusters. |
arrangement: terminal monochasia, dichasia, or condensed pleiochasia with 1–3 primary branches; individual pleiochasial branches unbranched or few-branched at 1 or more successive nodes; bracts subtending pleiochasia (pleiochasial bracts) opposite or whorled, usually wholly green or with paler green, white, pink, or red at base, sometimes wholly white, pink, or red, similar in shape and size to distal leaves or distinctly different, those on branches and subtending cyathia (dichasial and subcyathial bracts) opposite, distinct; additional cymose branches occasionally present in axils of distal leaves, but alternately arranged and without whorled bracts. |
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Cyathia | peduncle 0.9–1.5 mm. |
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x | = 7. |
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2n | = 28. |
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Euphorbia heterophylla |
Euphorbia sect. Poinsettia |
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Phenology | Flowering and fruiting nearly year-round. | |||||||||||||||||||||||||||||||||||||
Habitat | Disturbed areas, roadsides. | |||||||||||||||||||||||||||||||||||||
Elevation | 0–500 m. (0–1600 ft.) | |||||||||||||||||||||||||||||||||||||
Distribution |
Mexico; Central America; South America [Introduced, Ala., Ariz., Calif., Fla., Ga., La., Miss., N.Mex., Tex.; introduced also in Eurasia, Africa]
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North America; Mexico; Central America; South America; West Indies; Eurasia; Africa; Indian Ocean Islands; Pacific Islands; Australia |
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Discussion | Euphorbia heterophylla occurs from the southern United States, where it is likely naturalized, south through Mexico and Central America to South America. Because of its weediness, the precise native range in tropical and subtropical parts of the New World is not well understood. It has become widely established also in warm areas of the Old World. Leaf shape in this species is highly polymorphic within both populations and individuals. Euphorbia heterophylla can appear superficially similar to E. cyathophora but differs in its stipitate, circular involucral glands and its floral bracts that are at most very pale at the base (never colored as is typical in E. cyathophora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Species ca. 30 (10 in the flora). Section Poinsettia belongs to Euphorbia subg. Chamaesyce (Gray) Reichenbach. An expanded sect. Poinsettia is recognized here to include three species that have previously often been included in sect. Alectoroctonum (Schlechtendal) Baillon (E. bifurcata, E. eriantha, and E. exstipulata). These three species differ from the so-called core Poinsettia by the presence of involucral gland appendages, but they possess the shallowly to deeply concave involucral glands and toothed leaves that are generally diagnostic for the broader section. Molecular phylogenetic analyses clearly unite these three species with the other members of sect. Poinsettia and not with sect. Alectoroctonum (Y. Yang et al. 2012). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 323. | FNA vol. 12, p. 317. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia | ||||||||||||||||||||||||||||||||||||
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Synonyms | E. geniculata, Poinsettia geniculata, P. heterophylla | Poinsettia | ||||||||||||||||||||||||||||||||||||
Name authority | Linnaeus: Sp. Pl. 1: 453. (1753) | (Graham) Baillon: Étude Euphorb., 284. (1858) | ||||||||||||||||||||||||||||||||||||
Web links |