A N F Keys
1 Staminate and pistillate flowers distinct, not borne within an involucre; latex (if visible) clear or only cloudy
2 Blades conspicuously palmately lobed, 100−500 mm long; capsule spinescent .. Ricinus communis [pics]
2' Blades entire or finely toothed, short to 85 mm long; capsule not spinescent
3 Shoots glabrous; inflorescence spikelike; bractlet of flower having 2 trumpet-shaped glands; calyx absent; stamens 2 .. Stillingia linearifolia [pics]
3' Shoots hairy; inflorescence a cyme or racemelike; bractlet of flower without trumpet-shaped glands; calyx present, stamens 6 or more .. Croton
1' Staminate and pistillate flowers formed as a cyathium resembling a bisexual flower (involucre having 4 conspicuous nectary glands and both stamenlike staminate flowers and 1 stalked pistillate flower); latex copious and white .. Euphorbia
1 Dioecious perennial; shoots open-branched, covered by appressed, reflective, peltate-stellate hairs, each hair with center aging brownish; styles 3 and branched above; capsules 3-seeded .. Croton californicus [pics]
1' Monoecious annual; shoots intricately and regularly 3-branched, with mixed long, spreading unbranched and stellate hairs; style 1 and unbranched; capsules 1-seeded .. Croton setigerus [pics]
1 Shoots strongly planed (plagiotropic) with only opposite leaves; blades asymmetric at base, with stipules at base; fleshy appendage on seed (caruncle) absent (subgenus Chamaesyce)
2 Leaves and capsules with hairs
3 Perennial with many stems at base; blades entire; nectary glands burgundy to blackish with showy, wide, white appendages; staminate flowers 15 or more
4 Plants densely tomentose; appendages with hairs; cyathia 2−3 mm wide and capsules 1.5−2 mm long .. Euphorbia melanadenia
4' Plants sparsely hairy; appendages glabrous; cyathia 1.2−2.7 mm wide and capsules 1.3−1.6 mm long .. Euphorbia polycarpa [pics] (part)
3' Annual with conspicuous taproot; blades with short teeth; nectary glands yellowish green to yellowish orange or reddish with narrow whitish and pinkish appendages; staminate flowers 2−10
5 Capsules 1−1.2 mm long; nectary glands reddish .. Euphorbia prostrata [pics]
5' Capsules 1.3−1.8 mm long; nectary glands typically yellowish green to yellowish orange
6 Blades with teeth nearly to base, often with dark reddish central spot; cyathia < 1 mm wide; capsules short-strigose .. Euphorbia maculata [pics]
6' Blades with teeth only above midpoint, lacking central spot; cyathia 1−2 mm wide; capsules without appressed hairs .. Euphorbia serpyllifolia var. hirtula
2' Leaves and capsules glabrous
7 Nodal adventitious roots present or showing root buds; cyathia < 1 mm across .. Euphorbia serpens [pics]
7' Nodal adventitious roots absent; cyathia 1.3−4 mm across
8 Annual with conspicuous taproot; nectary glands with yellowish green or yellowish orange to reddish .. Euphorbia serpyllifolia var. serpyllifolia [pics]
8' Perennial with many stems at base; nectary glands purplish red to burgundy
9 Only lower stipules fused across node; capsules 1.3−1.6 mm long .. Euphorbia polycarpa [pics] (part)
9' Both lower and upper stipules fused across node; capsules 1.7−2 mm long .. Euphorbia albomarginata [pics]
1' Shoots not planed (orthotropic), strictly helically alternate or with lower leaves opposite decussate; blades symmetric at base, without stipules; fleshy appendage on seed (caruncle) present and often mushroomlike
10 Glands of cyathium with paired hornlike ends; seeds lacking netted ridges
11 Blades entire with a tapered base; capsules ca. 2 mm long, prominently 2-crested on each valve face; seeds whitish gray with vertical depressions .. Euphorbia peplus [pics]
11' Blades with small teeth and sometimes basal lobes; capsules 3.3−4 mm long, not 2-crested on valve face; seeds dark brown coated by tannish layer and minutely granular .. Euphorbia terracina [pics]
10' Glands of cyathium lacking hornlike ends; seeds with netted ridges
12 Cauline leaves opposite decussate and strongly 4-ranked, blades 30−150 mm long; capsules 6−12 mm long, sometimes minutely bumpy .. Euphorbia lathyris [pics]
12' Cauline leaves helically alternate; blades to 20 mm long; capsules ca. 2.5 mm long, conspicuously warty .. Euphorbia spathulata [pics]
The text of the above keys used with permission from
A Naturalist's Flora of the Santa Monica Mountains and Simi Hills, California
© Copyright
Barry A. Prigge and Arthur C. Gibson
2013