Euphorbia heterophylla |
Euphorbia platysperma |
|
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Mexican fireplant, painted euphorbia |
dune spurge, flat-seed spurge, flatseed sandmat |
|
Habit | Herbs, annual, with taproot. | Herbs, annual or short-lived perennial, with slender taproot. |
Stems | erect-ascending, 20–100 cm, sparsely pilose to villous; branches ± straight. |
prostrate, spreading and often mat-forming, 10–100 cm, glabrous. |
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; stipules usually distinct, occasionally connate basally, rarely to middle, subulate, narrowly triangular, or divided into 2–4 subulate segments, 0.5–1.1 mm, glabrous; petiole 1–3.6 mm, glabrous; blade oblong to obovate, 5–12 × 3–5 mm, base subsymmetric, cuneate to attenuate, margins entire, apex usually acute to mucronulate, rarely obtuse, surfaces glabrous; only midvein conspicuous. |
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. |
campanulate to obconic, 1.5–2 × 1.3–2.5 mm, glabrous; glands 4, yellowish, subcircular to oblong, 0.5–0.6 × 0.5–0.6 mm; appendages white, ovate to oblong or almost triangular, 0.3–0.6 × 0.3–0.8 mm, distal margin entire or shallowly 2–3-lobed. |
Staminate flowers | 8–15. |
45–50. |
Pistillate flowers | ovary glabrous or puberulent; styles 0.8–1.3 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous, styles 0.4–0.6 mm, 2-fid 1/2 length. |
Capsules | broadly ovoid, 2.8–3.8 × 4–5.3 mm, 3-lobed, usually glabrous, rarely sparsely puberulent; columella 2.1–2.8 mm. |
ovoid to ellipsoid, 2.7–3.2 × 2.2–2.9 mm, glabrous; columella 2.6–2.8 mm. |
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. |
whitish, pinkish, or light brown, ellipsoid-oblong, weakly dorsiventrally compressed and semielliptic in cross section, 2.2–2.5 × 1.3–1.6 mm, with sharp linelike longitudinal ridge on adaxial side, smooth and rounded on back. |
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. |
|
Cyathia | peduncle 0.9–1.5 mm. |
solitary at distal nodes; peduncle 1.6–4.1 mm. |
2n | = 28. |
|
Euphorbia heterophylla |
Euphorbia platysperma |
|
Phenology | Flowering and fruiting nearly year-round. | Flowering and fruiting year-round in response to sufficient moisture. |
Habitat | Disturbed areas, roadsides. | Sand dunes in Sonoran Desert scrub. |
Elevation | 0–500 m. (0–1600 ft.) | 60–200 m. (200–700 ft.) |
Distribution |
Mexico; Central America; South America [Introduced, Ala., Ariz., Calif., Fla., Ga., La., Miss., N.Mex., Tex.; introduced also in Eurasia, Africa]
|
AZ; CA; Mexico (Baja California, Sonora) |
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.) |
|
Source | FNA vol. 12, p. 323. | FNA vol. 12, p. 282. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | E. geniculata, Poinsettia geniculata, P. heterophylla | Chamaesyce platysperma |
Name authority | Linnaeus: Sp. Pl. 1: 453. (1753) | Engelmann: in W. H. Brewer et al., Bot. California 2: 482. (1880) |
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