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Key to families | Table of families and genera

Previous taxon Indexes to all accepted names and synonyms:
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Mark H. Mayfield & Grady L. Webster, except as noted

Annual to shrub, tree [vine, cactus-like succulent]; monoecious or dioecious; sap clear or milky. Stem: generally branched [fleshy or spiny]. Leaf: generally simple, alternate to whorled, generally stipuled, sessile or petioled; blade entire, toothed, or lobed. Inflorescence: flowers solitary or in terminal or axillary cymes, racemes, spikes, or panicles, or (in Euphorbia) 1° inflorescence a compact, flower-like cyathium with much-reduced flowers enclosed within an involucre of fused bracts, cyathia terminal or axillary, 1 or in cyme-like arrays. Flower: unisexual, ± radial; sepals 0 or 2–6, free or fused; petals generally 0(5); stamens 1–many, free or filaments fused; ovary superior, chambers (1)3(4), styles free or fused, undivided, forked, or variously lobed. Fruit: generally capsule that splits into mericarps that then dehisce, releasing seeds. Seed: 1 per chamber; knob-like appendage sometimes present at attachment scar.
217 genera, 6000+ species: ± worldwide especially tropics; some cultivated (Aleurites, tung oil; Euphorbia species; Hevea, rubber; Ricinus). Many species ± highly TOXIC, due primarily to latex, especially if eaten or in contact with skin, eyes. [Yang et al. 2012 Taxon 61:764–789] Eremocarpus moved to Croton, Tetracoccus moved to Picrodendraceae for TJM2; Chamaesyce moved to Euphorbia here (key to genera revised by Thomas J. Rosatti). —Scientific Editor: Bruce G. Baldwin.

Key to Euphorbiaceae


David J. Keil, Thomas J. Rosatti, Mark H. Mayfield & Daryl Koutnik

Annual to shrub [tree; fleshy, ± cactus-like], glabrous or hairy; sap milky; generally monoecious. Stem: prostrate to erect, generally < 1 m; branches arrayed around main stem(s) in 3-dimensions or 2-ranked, resulting in 2-faced stems with adaxial leaf faces all displayed to top side and abaxial leaf faces to bottom side. Leaf: proximal cauline, alternate or opposite, ± sessile to petioled; distal-most cauline in some species whorled, subtending umbel-like cluster of inflorescence branches, leafy bracts distal to whorled leaves generally opposite (whorled); stipules 0, gland-like, thread-like, or scale-like, free or fused, entire to divided; blade entire or toothed (pinnately lobed), base symmetric or asymmetric. Inflorescence: 1° inflorescence a cyathium, resembling a flower; cyathia 1–many, stalked or sessile, terminal (axillary), in generally leafy-bracted cyme-like arrays; cyathium a compact unit comprising an involucre of 5 fused bracts enclosing 1–many reduced staminate flowers and 1(0) pistillate flower; involucre generally 1–5 mm, bract tips alternate with 1–5 nectary glands (derived from modified stipules of involucral bracts), these transversely crescent-shaped or oblong to ± round, flat to cup-like, entire, toothed, or with 2 horn-like lobes, with or without distal, white to pink or red, flat, petal-like appendages; bractlets within involucre membranous or thread-like, often fringed. Staminate flower: (1–4)5–many, generally in 5 clusters around pistillate flower (this difficult to observe); calyx 0; each staminate flower a single stamen jointed to tip of a thread-like pedicel; pedicel persistent, stamen deciduous after pollen released. Pistillate flower: (0)1, central, stalked; calyx 0; ovary chambers 3, styles 3, free or fused at base, undivided or ± deeply forked. Fruit: stalk generally elongating, generally curved, pushing developing fruit from involucre; capsule ± spheric to ovoid or oblong, in ×-section ± round to 3-lobed or -angled. Seed: ± round or ± 3- or 4-angled (flattened) in ×-section, smooth or sculptured; knob-like appendage at attachment scar present or 0.
± 1750 species: warm and/or dry temperate to tropics worldwide. Euphorbus, physician to the King of Mauritania, 1st century [Horn et al. 2012 Molec Phylogen Evol 63:305–326] Forms monophyletic group with Chamaesyce, included here. Euphorbia serrata L. <Noxious weed> considered extirpated from California; 2003 report that Euphorbia exigua L. is possibly naturalizing as yet unconfirmed; Euphorbia marginata Pursh occasionally persisting from gardens, but recent records lacking. Euphorbia graminea Jacq. <Noxious weed> an urban weed. For fruit, seeds, "in ×-section" indicated only if not lobed or angled.
Unabridged references: [Wheeler 1936 Bull S Calif Acad Sci 35:127–147]

Key to Euphorbia

E. spathulata Lam. WARTY SPURGE
Annual, glabrous. Stem: 0.5–4.5 dm. Leaf: proximal cauline alternate, sessile or ± petioled; stipules 0; blade 1–3 cm, obovate to spoon-shaped, finely toothed, base symmetric, tapered, tip obtuse to notched; distal-most cauline in a whorl of 3(4). Inflorescence: 1° inflorescence branches in umbel-like cluster of 3(4) from axils of whorled leaves and also often from axils of distal alternate leaves; cyathia in leafy-bracted cyme-like clusters; bracts opposite, sessile, triangular-ovate, minutely toothed; involucre < 1.5 mm, bell-shaped; glands 4(5), < 1 mm, transversely oblong or elliptic; petal-like appendage 0. Staminate flower: 5–10. Pistillate flower: styles forked ± 1/2. Fruit: 2–3 mm, spheric, lobed, tubercled especially near tip and on lobes. Seed: 1.5–2 mm, ovoid, slightly flattened front-to-back, both sides convex, surface net-like; knob present.
Open, generally disturbed places; < 1300 m. California Floristic Province; to Washington, eastern North America, South America. Mar–Jun [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora,, accessed on Mar 27 2015
Citation for this treatment: [Author of taxon treatment] 2013. Euphorbia, Revision 1, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Mar 27 2015

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Geographic subdivisions indicated for the distribution of Euphorbia spathulata Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.