Flora of North America species comparison

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Euphorbia heterophylla

Euphorbia ouachitana

Mexican fireplant, painted euphorbia
Habit Herbs, annual, with taproot. Herbs, annual, with taproot.
Stems

erect-ascending, 20–100 cm, sparsely pilose to villous;

branches ± straight.

erect-ascending, often basally decumbent, often branched near base, 12–28 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.

petiole 0–3 mm;

blade broadly oblanceolate to subspatulate, or proximalmost often orbiculate, 3–20 × 3–9 mm, base attenuate, margins entire, apex rounded to emarginate, surfaces glabrous;

venation pinnate, midvein prominent.
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.

infundibular, 1.3–1.6 × 1–1.2 mm, glabrous;

glands 4, crescent-shaped; 0.4–0.5 × 0.8–1 mm;

horns divergent, 0.2–0.4 mm.
Staminate flowers

8–15.

15–20.
Pistillate flowers

ovary glabrous or puberulent;

styles 0.8–1.3 mm, 2-fid 1/2 to nearly entire length.

ovary glabrous;

styles 0.8 mm, 2-fid.
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-globose, 2.6–2.7 × 2.5–2.7 mm, slightly lobed;

cocci rounded to ± flattened, smooth, glabrous;

columella 2–2.1 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.

dark brown, oblong-ovoid, 1.5–2 × 1–1.6 mm, with deep, rounded pits in 3–4 regular vertical rows;

caruncle reniform-ovate, conic, 0.5–0.7 × 0.5–0.8 mm.
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 pleiochasial branches 3, 1–3 times 2-branched;

pleiochasial bracts ovate-deltate to subrhombic-ovate, shorter and wider than distal leaves;

dichasial bracts connate 1/4 length, not imbricate, broadly deltate to subreniform, base truncate to broadly obtuse, margins entire, apex obtuse to bluntly acuminate;

axillary cymose branches 1–5.
Cyathia

peduncle 0.9–1.5 mm.

peduncle 0.4–0.7 mm.
2n

= 28.

= 26.

Euphorbia heterophylla

Euphorbia ouachitana
Phenology Flowering and fruiting nearly year-round. Flowering and fruiting spring.
Habitat Disturbed areas, roadsides. Semiopen forests, bluffs and ledges, stream banks, glades.
Elevation 0–500 m. (0–1600 ft.) 100–400 m. (300–1300 ft.)
Distribution
from USDA
Mexico; Central America; South America [Introduced, Ala., Ariz., Calif., Fla., Ga., La., Miss., N.Mex., Tex.; introduced also in Eurasia, Africa]
[WildflowerSearch map]
[BONAP county map]
from FNA
AR; MO; OK; TN; TX
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.)

Euphorbia ouachitana is restricted to semiopen forests and woodlands in the south-central United States. It is similar to E. commutata and has been most commonly identified as that species in the past. However, it differs in its consistently brown seeds that have pits in regular, vertical rows. The two species also differ in E. commutata’s numerous, proximal, long-petiolate elliptic leaves. The proximal leaves of E. ouachitana are spatulate with an orbiculate blade and petiolelike base. Aside from the restricted distribution of E. ouachitana in Missouri and Tennessee, the ranges of E. ouachitana and E. commutata do not overlap (see M. H. Mayfield 2013 for a detailed discussion of the distribution). Euphorbia ouachitana is most common in the Ouachita Mountains from southeastern Oklahoma to Hot Springs County, Arkansas.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 323. FNA vol. 12, p. 306.
Parent taxa Euphorbiaceae > Euphorbia > sect. Poinsettia Euphorbiaceae > Euphorbia > subg. Esula
Sibling taxa
E. aaron-rossii, E. abramsiana, E. acuta, E. agraria, E. albomarginata, E. alta, E. angusta, E. antisyphilitica, E. arizonica, E. astyla, E. austrotexana, E. bicolor, E. bifurcata, E. bilobata, E. blodgettii, E. bombensis, E. brachycera, E. capitellata, E. carunculata, E. chaetocalyx, E. chamaesula, E. cinerascens, E. commutata, E. conferta, E. cordifolia, E. corollata, E. crenulata, E. cumulicola, E. cuphosperma, E. curtisii, E. cyathophora, E. cyparissias, E. davidii, E. deltoidea, E. dendroides, E. dentata, E. discoidalis, E. eriantha, E. exigua, E. exserta, E. exstipulata, E. falcata, E. fendleri, E. florida, E. floridana, E. garberi, E. georgiana, E. geyeri, E. glyptosperma, E. golondrina, E. gracillima, E. graminea, E. helioscopia, E. helleri, E. hexagona, E. hirta, E. hooveri, E. humistrata, E. hypericifolia, E. hyssopifolia, E. indivisa, E. innocua, E. inundata, E. ipecacuanhae, E. jaegeri, E. jejuna, E. laredana, E. lasiocarpa, E. lata, E. lathyris, E. longicruris, E. lurida, E. macropus, E. maculata, E. marginata, E. meganaesos, E. melanadenia, E. mendezii, E. mercurialina, E. mesembrianthemifolia, E. micromera, E. misera, E. missurica, E. myrsinites, E. nephradenia, E. nutans, E. oblongata, E. ocellata, E. ophthalmica, E. ouachitana, E. parishii, E. parryi, E. pediculifera, E. peplidion, E. peplus, E. perennans, E. pergamena, E. pinetorum, E. platyphyllos, E. platysperma, E. polycarpa, E. polygonifolia, E. polyphylla, E. porteriana, E. prostrata, E. pubentissima, E. purpurea, E. radians, E. rayturneri, E. revoluta, E. roemeriana, E. rosescens, E. schizoloba, E. serpens, E. serpillifolia, E. serrata, E. serrula, E. setiloba, E. simulans, E. spathulata, E. stictospora, E. strictior, E. telephioides, E. terracina, E. tetrapora, E. texana, E. theriaca, E. thymifolia, E. tithymaloides, E. trachysperma, E. trichotoma, E. vallis-mortae, E. velleriflora, E. vermiculata, E. villifera, E. virgata, E. wrightii, E. yaquiana
E. aaron-rossii, E. abramsiana, E. acuta, E. agraria, E. albomarginata, E. alta, E. angusta, E. antisyphilitica, E. arizonica, E. astyla, E. austrotexana, E. bicolor, E. bifurcata, E. bilobata, E. blodgettii, E. bombensis, E. brachycera, E. capitellata, E. carunculata, E. chaetocalyx, E. chamaesula, E. cinerascens, E. commutata, E. conferta, E. cordifolia, E. corollata, E. crenulata, E. cumulicola, E. cuphosperma, E. curtisii, E. cyathophora, E. cyparissias, E. davidii, E. deltoidea, E. dendroides, E. dentata, E. discoidalis, E. eriantha, E. exigua, E. exserta, E. exstipulata, E. falcata, E. fendleri, E. florida, E. floridana, E. garberi, E. georgiana, E. geyeri, E. glyptosperma, E. golondrina, E. gracillima, E. graminea, E. helioscopia, E. helleri, E. heterophylla, E. hexagona, E. hirta, E. hooveri, E. humistrata, E. hypericifolia, E. hyssopifolia, E. indivisa, E. innocua, E. inundata, E. ipecacuanhae, E. jaegeri, E. jejuna, E. laredana, E. lasiocarpa, E. lata, E. lathyris, E. longicruris, E. lurida, E. macropus, E. maculata, E. marginata, E. meganaesos, E. melanadenia, E. mendezii, E. mercurialina, E. mesembrianthemifolia, E. micromera, E. misera, E. missurica, E. myrsinites, E. nephradenia, E. nutans, E. oblongata, E. ocellata, E. ophthalmica, E. parishii, E. parryi, E. pediculifera, E. peplidion, E. peplus, E. perennans, E. pergamena, E. pinetorum, E. platyphyllos, E. platysperma, E. polycarpa, E. polygonifolia, E. polyphylla, E. porteriana, E. prostrata, E. pubentissima, E. purpurea, E. radians, E. rayturneri, E. revoluta, E. roemeriana, E. rosescens, E. schizoloba, E. serpens, E. serpillifolia, E. serrata, E. serrula, E. setiloba, E. simulans, E. spathulata, E. stictospora, E. strictior, E. telephioides, E. terracina, E. tetrapora, E. texana, E. theriaca, E. thymifolia, E. tithymaloides, E. trachysperma, E. trichotoma, E. vallis-mortae, E. velleriflora, E. vermiculata, E. villifera, E. virgata, E. wrightii, E. yaquiana
Synonyms E. geniculata, Poinsettia geniculata, P. heterophylla
Name authority Linnaeus: Sp. Pl. 1: 453. (1753) Mayfield: J. Bot. Res. Inst. Texas 7: 642, figs. 2[row 2, right], 6. (2013)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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