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sun spurge

weak spurge

Habit Herbs, perennial, with moniliform tuberous rootstock. Herbs, annual, with taproot.
Stems

erect, 5–20(–30) cm, usually glabrous, occasionally puberulent;

branches ± straight.

erect, unbranched, 7–20 cm, glabrous.

Leaves

alternate;

petiole 0–2 mm, glabrous or strigose;

blade linear-lanceolate to ovate or broadly elliptic, 25–50 × 3–20 mm, unlobed, base rounded (tapered to petiole), margins with few glandular teeth, strigillose, flat to revolute, apex acute, abaxial surface coarsely strigose, adaxial surface strigose-hirsute;

venation pinnate, midvein prominent.

petiole 1–2 mm, reduced distally;

blade spatulate-cuneate, 8–10 × 4–5 mm (greatly reduced in size proximally), base cuneate, margins entire, apex rounded to emarginate or obcordate, surfaces glabrous;

venation pinnate.

Involucre

broadly globose-cupulate, 1.7–2.1 × 2.2–2.5 mm, glabrous or puberulent;

involucral lobes divided into triangular segments;

glands 1–4(–5), white, sessile and broadly attached, 1.1 × 1.4 mm, opening oblong, glabrous;

appendages absent.

campanulate, 0.8–1.1 × 0.7–1 mm, glabrous;

glands 4, elliptic to trapezoidal, 0.3–0.6 × 0.6–1.2 mm;

horns divergent, 0.5–1 mm.

Staminate flowers

20–25.

10–15.

Pistillate flowers

ovary glabrous or puberulent, styles 3–4 mm, 2-fid 1/2 to nearly entire length.

ovary smooth, glabrous;

styles 0.6–1 mm, 2-fid.

Capsules

depressed-globose, 3.8–5 × 4–5 mm, 3-lobed, glabrous or puberulent;

columella 3.6–4.5 mm.

depressed-globose, 1.8–2.2 × 2.2–2.9 mm, slightly lobed;

cocci rounded to slightly flattened, smooth, glabrous;

columella 1.5–1.8 mm.

Seeds

white, mottled brown to gray, ellipsoid, rounded in cross section, 4–4.6 × 2.4–3.2 mm, smoothly and broadly pitted or grooved;

caruncle 0.1 mm.

reddish brown to brown, often glaucous, oblong, 1.3–1.4 × 0.8–0.9 mm, abaxial faces with 15–20 shallow pits or almost smooth, adaxial faces with 4–6 large shallow pits or irregular oblong grooves;

caruncle conic, hat-shaped, 0.3–0.4 × 0.4–0.6 mm.

Cyathial

arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched (often highly condensed);

pleiochasial bracts 6–8(–10), as tight involucrate whorl, wholly white to pale pink or red, usually narrower than distal leaves;

dichasial bracts linear and highly reduced.

arrangement: terminal pleiochasial branches 3, each 1–3(–4) times 2-branched;

pleiochasial bracts obovate, similar in size to distal leaves;

dichasial bracts distinct or basally subconnate, not imbricate, triangular-ovate, base truncate or cordate, margins entire, apex mucronate;

axillary cymose branches 1–4.

Cyathia

peduncle 2–5.5 mm.

peduncle 0.2–0.6 mm.

Euphorbia radians

Euphorbia tetrapora

Phenology Flowering and fruiting spring–summer. Flowering and fruiting spring.
Habitat Pinyon-juniper woodlands, oak savannas, desert grasslands and scrub. Sandy soils, dry open woods.
Elevation 700–2500 m. (2300–8200 ft.) 0–300 m. (0–1000 ft.)
Distribution
from FNA
AZ; TX; Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
LA; OK; TX
[BONAP county map]
Discussion

Euphorbia radians is widely distributed but scattered from the Sonoran and Chihuahuan deserts south to Oaxaca in Mexico. The species is distinct among species in sect. Poinsettia in the flora area in its precocious habit, often flowering before the leaves emerge.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Euphorbia tetrapora is endemic to a portion of the western Gulf coastal plain. D. S. Correll and M. C. Johnston (1970) included Alabama and Georgia in the distribution of this species as well, probably due to Engelmann’s citation of a Georgia specimen from the herbarium of Samuel Boykin. Whether the Boykin specimen came from Georgia, where Boykin was based, is unclear. Because no records to support its occurrence in the eastern Gulf coastal plain (Alabama or Georgia) have been found, those states are here excluded from the distribution of E. tetrapora.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 12, p. 324. FNA vol. 12, p. 311.
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. 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. 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. 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. 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. 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 Poinsettia radians Tithymalus tetraporus
Name authority Bentham: Pl. Hartw., 8. (1839) Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 191. (1859)
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