Euphorbia prostrata |
Euphorbia exserta |
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blue weed, ground spurge, prostrate sandmat, prostrate spurge or sandmat |
coastal sand spurge, maroon or purple sand spurge |
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Habit | Herbs, annual, with taproot. | Herbs, perennial, with spreading rootstock. |
Stems | prostrate to decumbent, usually not mat-forming, 10–30 cm, crisped-villous to glabrate (proximally). |
erect or ascending, unbranched or branched, solitary, few, or occasionally densely clumped, previous year's dead stems not persistent, 20–33 cm, usually glabrous, rarely sparsely villous, glaucescent. |
Leaves | opposite; stipules connate (lower side) or distinct (upper side), triangular-subulate, often lacerate distally, 0.5–1 mm, short crisped-villous to glabrate; petiole 0.5–1.5 mm, usually short crisped-villous, sometimes wooly at distal nodes; blade broadly elliptic to elliptic-oblong, ovate-spatulate, or ovate, 3–11(–15) × 3–6(–8) mm, base slightly asymmetric, rounded to slightly cordate and oblique, margins serrulate at least in distal 1/2, sometimes obscurely so, apex obtuse, abaxial surface finely crisped-villous, adaxial surface usually glabrous or glabrate, sometimes sparsely crisped-villous; 3-veined from base. |
alternate; stipules less than 0.1 mm; petiole (0–)1–3 mm, glabrous; blade linear or linear-elliptic to obovate or orbiculate, proximal greatly reduced, scalelike, 15–30 × 1–20 mm, base cuneate to rounded, margins entire, apex rounded, broadly acute, or emarginate, surfaces glabrous, glaucescent; venation often obscure on narrow leaves, midvein conspicuous. |
Involucre | obconic, 0.6–0.9 × 0.5 mm, crisped-villous or glabrous; glands 4, reddish, oval to oblong, 0.1 × 0.1–0.2 mm; appendages white to pink, rudimentary, 0–0.2 mm, distal margin entire or irregularly scalloped. |
usually dark red, campanulate, 1.3–1.6 × 1.4–2.1 mm, glabrous; glands 5, usually dark red, rarely greenish red, elliptic reniform, thickened, 0.3–0.5 × 0.8 mm; appendages white or green, often forming narrow rim around distal margin of gland, 0–0.2 mm, entire. |
Staminate flowers | 3–6. |
20–25. |
Pistillate flowers | ovary densely crisped-villous; styles 0.1 mm, 2-fid nearly entire length. |
ovary glabrous; styles 0.4–0.8 mm, 2-fid at apex. |
Capsules | broadly ovoid, 1.2–2 × 1.4–1.5 mm, crisped-villous along keels and toward base, often glabrous between keels; columella 1–1.2 mm. |
depressed-globose, 1.8–2.5 × 3.6–4.4 mm, glabrous; columella 1.9–2.4 mm. |
Seeds | white but with barely concealed brown surface beneath, ovoid, sharply 4-angled in cross section, abaxial faces plane to convex, adaxial faces concave, 0.8–1.1 × 0.5–0.7 mm, with several narrow, sharp, slightly irregular, transverse ridges. |
ashy white, ovoid, 2.1 × 1.3 mm, angled with 5 blunt longitudinal ridges, with shallow and irregular pits; caruncle absent. |
Cyathia | solitary or in small, cymose clusters at distal nodes or on congested, axillary branches; peduncle 1–2 mm. |
usually in terminal dichasia, sometimes pleiochasia; peduncle 6–33 mm, filiform, glabrous. |
2n | = 18. |
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Euphorbia prostrata |
Euphorbia exserta |
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Phenology | Flowering and fruiting early spring–fall. | Flowering and fruiting spring–summer. |
Habitat | Disturbed areas, fields, gardens, sidewalks, sandy places, ballast piles. | Xeric to dry pine-oak scrub of sand hills, pine-oak woodlands, pine-oak savannas. |
Elevation | 0–1400 m. (0–4600 ft.) | 0–150 m. (0–500 ft.) |
Distribution |
AL; AR; AZ; CA; CO; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MO; MS; NC; NE; NM; OH; OK; PA; SC; SD; TN; TX; UT; VA; WV; WY; Mexico; Central America; South America; West Indies [Introduced in Eurasia, Africa, Pacific Islands, Australia]
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FL; GA; NC; SC; VA
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Discussion | Euphorbia prostrata is native to tropical America and possibly into the southern part of the flora area. It is likely adventive throughout most of the northern part of its range. It is widely naturalized throughout much of the rest of the tropics. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
K. R. Park (1998) recognized both Euphorbia exserta and E. gracilior as distinct species, with the former known only from the holotype. However, this treatment follows M. J. Huft (1997) and treats E. gracilior as a synonym of E. exserta. Although the type of E. exserta is unusual in having greenish red (versus dark red) cyathia and glands, as well as small gland appendages, it is otherwise typical of the species as a whole, including features such as the upright habit, reddish coloration, scalelike proximal leaves, and filiform peduncles to 30 mm that are also common to plants formerly treated as E. gracilior. Euphorbia gracilis Elliott, which has sometimes been applied to E. exserta, is an illegitimate name (a later homonym of E. gracilis Loiseleur-Deslongchamps) and pertains here. The upright habit and usually dark red cyathia and glands distinguish Euphorbia exserta from the otherwise similar E. ipecacuanhae, while the glaucescent vegetative parts and smaller gland appendages readily separate E. exserta from the similar E. curtisii. Euphorbia exserta is found on the Gulf and Atlantic coastal plains. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 285. | FNA vol. 12, p. 246. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Synonyms | Chamaesyce prostrata | Tithymalopsis exserta, E. gracilior, T. gracilis |
Name authority | Aiton: Hort. Kew. 2: 139. (1789) | (Small) Coker: Pl. Life Hartsville, 88. (1912) |
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