Colors

Data mode

Account

Login
Sign up

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Euphorbia

1 Shrubs with succulent stems; [subgenus Euphorbia, sect. Crepidaria].
..2 Stems zigzag
..2 Stems straight
1 Herbs.
....3 Leaves strictly opposite, oblique or inequilateral at base; branches prostrate (less usually erect); [subgenus Chamaesyce; section Anisophyllum]
....3 Leaves alternate or opposite, not oblique or asymmetric at base; branches usually erect.
......4 Bracteal leaves lobed or toothed (rarely linear), usually marked with red or white at the base or purple-spotted; glands of the cyathia usually 1 (rarely more), bilabiate, lacking petaloid appendages; [subgenus Chamaesyce; section Poinsettia]
......4 Bracteal leaves entire, not marked with red (white-margined in E. marginata); glands of the cyathia 4-5, flattish, not bilabiate, with or without petaloid appendages.
........5 Glands of the cyathia 5 (or 7-10 on the central cyathium in E. pubentissima), with petaloid appendages 0.1-5.0 mm long (measured along a radius), these white, maroon, red, pink, or green; stipules present, glandlike, often minute; [subgenus Chamaesyce; section Alectoroctonum]
........5 Glands of the cyathia 4 (except 5 in E. purpurea), oval, reniform, or crescent-shaped, lacking petaloid appendages (the glands themselves yellowish or green); stipules absent or vestigial
..........6 Ovary and capsule subtended by a calyx-like structure; seeds without caruncles; involucral gland appendages absent; [subgenus Euphorbia; section Nummulariopsis]
..........6 Ovary and capsule not subtended by a calyx-like structure; seeds with caruncles; involucral gland appendages hornlike or absent; [subgenus Esula]

Key to Euphorbia, Key A: subgenus Chamaesyce, section Anisophyllum, subsection Hypericifoliae {add to Key A: E. blodgettii, E. hypericifolia, E. mesembrianthemifolia, E. ophthalmica, E. serpyllifolia var. serpyllifolia}

1 Young stems and leaves glabrous; leaves either entire or serrulate, at least at the apex (use 10× magnification).
..2 Leaves serrulate, at least at the apex (use 10× magnification); seeds with 2-4 transverse ridges.
....3 Seeds 1.0-1.3 mm long, with 3-4 transverse ridges
....3 Seeds 0.8-1.0 mm long, with 2-3 (-4) transverse ridges
..2 Leaves absolutely entire; seeds smooth.
......4 Stipules united into a triangular scale-like structure (this often lobed or fringed), thus appearing as 2 stipules at each node
......4 Stipules separate, lacerate, appearing as 3 or 4 stipules at each node.
........5 Mature seeds bluntly angled or subangled in cross section, 1.0-1.4 (1.6) mm long (except for 1.8-2.1 mm long in E. cordifolia); leaves either 1.5-2× or 4-5× as long as wide, not fleshy; [sandy inland habitats or coastal dunes in E. cumulicola].
..........6 Leaves 1.5-2× as long as wide, green throughout; [more widespread].
..........6 Leaves 4-5× as long as wide, the leaf margin red; [FL]
............ 7 Seeds ashy white with a brown longitudinal line on adaxial surface, 1.1-1.4 (-1.6) mm long; leaf bases angled or rounded, with one side of the leaf base often expanded into a small rounded auricle
............ 7 Seeds gray or tan with dark brown mottling, 1.8-2.1 mm long; leaf bases cordate to rounded, without an auricle on one side
........5 Mature seeds rounded in cross section, (1.3-) 1.5-2.6 mm long; leaves 2-3 (-5)× as long as wide, often somewhat fleshy; [of barrier island dunes and other sandy coastal habitats].
............ ..8 Mature seeds (1.3-) 1.5-1.9 mm long; cyathia terminal on the stems and also axillary
............ ..8 Mature seeds (2.0-) 2.2-2.6 mm long; cyathia terminal on the stems
1 Young stems and leaves pubescent (at least in lines along the stems); leaves serrulate, at least at the apex (use 10× magnification).
............ ....9 Ovary and capsule glabrous.
............ ......10 Seeds 0.8-1.0 mm long, light gray, the faces with 2-3 (-4) horizontal, low, blunt ridges, sometimes connected by 1-2 cross ridges; stems glabrous when young (uncommonly puberulent along 1 side of the branchlets); capsule 1.5-2.0 mm long
............ ......10 Seeds 1.0-1.3 mm long, dark gray, faces without ridges, though irregularly and finely wrinkled; stems puberulent when young on 1 side only; capsule 2.0-2.5 mm long.
............ ........11 Stems ascending or suberect, puberulent when young
............ ........11 Stems prostrate or widely spreading, spreading-hirsute
............ ....9 Ovary and capsule pubescent.
............ ..........12 Stems with 2 types of trichomes, the longer 3-5 mm long; cyathia in axillary and terminal cymes, at least some of the peduncles > 10 mm long
............ ..........12 Stems with 1 type of trichome, these < 2 mm long; cyathia solitary or several in axils, the peduncles < 5 mm long.
............ ............ 13 Capsules spreading-villous, especially or solely on the angles; styles 0.2-0.3 mm long, bifid nearly to the base; seeds sharply quadrangular-angled, the faces with 3-4 transverse ridges
............ ............ 13 Capsules minutely appressed-puberulent, on the entire surface (though sometimes primarily on the lower portion); styles 0.3-0.7 mm long, bifid only in the upper half or third; seeds quadrangular but not angled, the faces with inconspicuous transverse ridges or nearly smooth.
............ ............ ..14 Involucre cleft on 1 side half its length; leaves mostly obovate, 1.5-2× as long as wide; styles 0.5-0.7 mm long, filiform; seed faces nearly smooth; adventitious roots formed at middle nodes along the stem
............ ............ ..14 Involucre cleft on 1 side a fourth to a third its length; leaves mostly oblong, 2-3× as long as wide; styles 0.3-0.4 mm long, clavate; seed faces transversely ridged; adventitious roots not formed

Key to Euphorbia, Key B: subgenus Chamaesyce, section Poinsettia

1 Principal stem leaves opposite, dentate, neither lobed nor linear; plant pubescent.
..2 Leaf undersurface hairs stiff and distinctly widened towards their bases; capsules 4.0-4.8 mm wide; seeds angular in cross section, unevenly tuberculate
..2 Leaf undersurface hairs soft and little or not thickened towards their bases; capsules 3.5-4.0 mm wide; seeds rounded in cross section, evenly tuberculate
1 Principal stem leaves alternate, either lobed or linear; plant usually glabrous.
....3 Cyathial gland with a circular opening; bracteal leaves wholly green or green and paler at base (sometimes purple-spotted); seeds angular, with a small caruncle and pronounced longitudinal dorsal ridge, but lacking a distinct transverse tubercular ridge near the middle
....3 Cyathial gland 2-lipped, the opening elliptical and elongate; bracteal leaves wholly green, purple, white, pink, or red, or green or purplish towards the tip and white, pink, or red at the base; seeds cylindrical, lacking both a caruncle and longitudinal dorsal ridge, but with a distinct transverse tubercular ridge near the middle.
......4 Annual herbs from spreading taproots; leaf blades 4-40 mm wide; bracteal leaves usually green with white, pink, or red at base, or some or all bracts wholly white, pink, red, or green; capsules green at maturity; involucral glands 1; [widespread in our region]
......4 Perennial herbs with thick, woody taproots; bracteal leaves usually purplish green (or with pink at base); capsules purplish at maturity; involucral glands 3-5; [s. FL]

Key to Euphorbia, Key C: subgenus Chamaesyce, section Alectoroctonum

1 Upper stem leaves and/or dichasial bracts with white margins or entirely white.
..2 Cyathial bracts glabrous, often entirely white (less commonly only white along margins)
..2 Cyathial bracts densely pilose, with conspicuous white margins.
....3 Leaf surfaces pilose; cyathial bracts linear to narrowly oblanceolate; seeds 4.3-4.5 mm long
....3 Leaf surfaces glabrous; cyathial bracts narrowly elliptic to oblanceolate; seeds 3.7-3.9 mm long
1 Upper stem leaves and bracteal leaves entirely green, not whitened.
......4 Leaves opposite, linear-filiform; [primarily of the c. US, w. of the MS river]
......4 Leaves alternate, variously shaped (linear to ovate); [widespread, including c. US].
........5 Petaloid appendages (0.5-) 1.0-4.4 mm long (measured along a radius), about as long as wide or longer, white; stems 1.4-9 (-11) dm tall, erect or ascending.
..........6 Leaves broad (ovate, oblanceolate, elliptic, or lanceolate), < 5.5× as long as wide; leaf blades slightly revolute or planar; glands green.
............ 7 Involucral glands 4; leaf adaxial (upper) surface densely pilose; leaf bases cordate
............ 7 Involucral glands 5; leaf adaxial (upper) surface usually glabrous (besides ciliate margins in E. apocynifolia); leaf bases cuneate to rounded.
............ ..8 Petioles 5-11 mm long; leaves with ciliate margins; cyathia across the appendages ca. 2.5 mm; nodes 7-11 below the umbels; [shady, mesic hardwood forests over limestone or in sand over limestone]
............ ..8 Petioles 0-3.5 (-10) mm long; leaves without ciliate margins; cyathia across the appendages (3.5-) 4–8 (-11) mm; nodes 20-75 nodes below the umbels; [habitats various, generally open, drier, and acidic, e.g., pine woods, sandhills, sandstone, ruderal sites]
............ ....9 Plants (2-) 4-9 (-13) dm tall; aerial stems multiple, (1-) 3-10 stems from a crown, each (1.2-) 2.5-5 (-7) mm in diameter at the base; leaves ascending, leathery, sessile; primary bracts smaller than stem leaves; petaloid appendages oblong or spatulate, 2.5-4.4 mm long; seeds 2.6-3.2 mm long; [NH and MA west to s. ON, MI, WI, MN, and NE, south to se.VA, c. NC, n. GA, s. AL, and e. TX]
............ ....9 Plants 3.5-6.5 dm tall; aerial stems 1 (-3) from a crown, each 1.0-2.2 mm in diameter at the base; leaves usually reflexed, thin, petiolate or subpetiolate; primary bracts similar to stem leaves in size; petaloid appendages orbicular or oval, 0.9-2.2 mm long; seeds 1.8-2.3 mm long; [c. MD, VA, and c. and sw. TN, south to Panhandle FL and s. MS]
..........6 Leaves linear, > 8× as long as wide); leaf blades conspicuously revolute or involute; glands green or dark purple.
............ ......10 Main stem not branching at base, erect or ascending, usually densely pubescent, dark grey or green; leaves not succulent, revolute, petiolate; stipules obsolete; glands green or rarely purple; petaloid appendages entire; [e. and c. GA (or e. SC?) south and west to Panhandle FL and e. TX]
............ ......10 Main stem branching at base, ascending or spreading, glabrous, green or greenish purple; leaves succulent, involute, sessile or short petiole; stipules present and glandular; glands purple; petaloid appendages deeply crenate; [c. and s. peninsular FL]
........5 Petaloid appendages 0.05-0.6 mm long (measured along a radius), shorter than wide, green, red, white, or pink; stems (0.8-) 1.5-4.5 (-6) dm tall, erect, ascending or decumbent; leaves ciliate-margined (E. mercurialina and E. curtisii) or not.
............ ........11 Leaf margins ciliate; cyathia 3.5-5.9 mm wide (across the appendages), green; leaves not fleshy, 1.7-2.2 (-3)× as long as wide, not especially variable; [of mesic forests with rich soils]
............ ........11 Leaf margins not ciliate (except some marginal hairs in E. curtisii); cyathia 2.0-3.4 mm wide (across the appendages), green or maroon; leaves slightly to strongly fleshy, 0.7-20× as long as wide, often very variable in shape, even on the same plant; [of more or less xeric sandhill woodlands with acidic, sandy soils].
............ ..........12 Stems usually 10-18 per crown, decumbent to weakly ascending; leaves opposite (scales on the lower stem sometimes alternate), fleshy, blue-green with a narrow, thickened, red-hyaline margin; branching dichotomous from the base of the plant (the branches typically equal, though sometimes unequal)
............ ..........12 Stems 1-4 (-9) per crown, erect to strongly ascending; leaves alternate, opposite, or in whorls of 3 (at least some alternate on a plant), less fleshy, green to blue-green, without a red margin (or with a very narrow, slightly red-hyaline, but not thickened margin in E. exserta); branching alternate below the inflorescence (rarely dichotomous or trichotomous), the branches typically unequal.
............ ............ 13 Cyathia and capsules green; petaloid appendages white or pink; leaves thin-textured, green, finely pubescent with appressed white hairs (0.1-0.3 mm long) on the lower surface and margins (visible at 10× or greater); branching primarily alternate; leaves primarily alternate (typically opposite or 3-whorled below the inflorescence); cyathia unisexual, plants usually unisexual (dioecious)
............ ............ 13 Cyathia and capsules maroon; petaloid appendages maroon-red; leaves slightly fleshy, somewhat blue-green, glabrous; branching primarily opposite; leaves primarily opposite (usually some alternate on upper branches); cyathia bisexual, plants bisexual

Key to Euphorbia, Key E: subgenus Esula

1 Principal stem leaves finely serrulate (especially toward the apex); [subgenus Esula, section Helioscopia].
..2 Ovary and capsule smooth
....3 Leaf margins crenulate, the teeth rounded; terminal pleiochasial branches (rays) usually 3 and not or less radiant from above; capsules 1.6–2 mm long; seeds 1.4–1.5 mm long; [endemic to southeastern TX and adjacent LA
....3 Leaf margins serrulate, the teeth pointed; terminal pleiochasial branches (rays) usually 5 and conspicuously radiating from above; capsules 2.5–4 mm long; seeds 1.6–2.2 mm long [uncommon non-native of disturbed areas in e. US]
..2 Ovary and capsule verrucose-roughened.
......4 Plants perennial, with thickened woody taproots; stems villous (often densely so, especially on inflorescence branches); leaves to 25 mm wide; [non-native waif]
......4 Plants annual, rarely biennial, with thin herbaceous to only partially woody taproots; stems glabrous (or occasionally pilose in E. platyphyllos); leaves to 11 mm wide; [natives and waifs].
........5 Leaves sparsely pilose, usually with acute apices; plants usually with 5 terminal pleiochasial branches; [non-native waif, disturbed areas]
........5 Leaves glabrous, usually with obtuse or rounded apices; plants usually with 3 terminal pleiochasial branches; [natives of intact and disturbed areas].
..........6 Seeds smooth or very obscurely reticulate, 1.7-2.5 mm long; cyathia with the involucre 1.2-1.5 mm long; involucral bracts typically red; dichasial bracts cordate-clasping
..........6 Seeds distinctly alveolate, 1.3-1.8 mm long; cyathia with the involucre 0.6-0.9 mm long; involucral bracts typically yellow; dichasial bracts rounded to subcordate
1 Principal stem leaves entire.
............ 7 Stem leaves opposite, decussate (each succeeding pair turned by 90 degrees); seeds 4-6 mm long; [subgenus Esula, section Lathyris]
............ 7 Stem leaves alternate (or mostly so); seeds 1-3 mm long.
............ ..8 Stem leaves linear to narrowly oblong, 10-90 mm long (5-30 mm long in E. cyparissias), averaging ca. 10× as long as wide; [subgenus Esula, section Esula].
............ ....9 Stem leaves 10-30 mm long, (5-)10-30 mm wide
............ ....9 Stem leaves 30-80 mm long, 3-8(-12) mm wide
............ ..8 Stem leaves oblanceolate, obovate, elliptic, spatulate, or oblong, 10-100 (-150) mm long, (3-)5-30 mm wide, averaging 1-5× as long as wide.
............ ......10 Principal stem leaves elliptic to oblong, (50-) 70-100 cm long; rhizomatous perennial to 1 m tall; seeds smooth, 3-5 mm long; rays of the umbel usually 5-8; [subgenus Esula, section Helioscopia]
............ ......10 Principal stem leaves oblanceolate to obovate, 10-20 mm long; annual, biennial, or perennial by basal offshoots, to 0.4 m tall; seeds pitted, 1.3-2.0 mm long; rays of the umbel 3 (-5).
............ ........11 Seeds pitted only on one face, the inner face furrowed; [subgenus Esula, section Tithymalus]
............ ........11 Seeds pitted on both the inner and outer faces.
............ ..........12 Seeds coarsely pitted with transversely elongate pits in 4 vertical rows (appearing nearly transversely rugose); glands of the cyathia crescent-shaped, the horns short and blunt; [subgenus Esula, section Pithyusa]
............ ..........12 Seeds either finely pitted with numerous, evenly distributed, isodiametric pits, or tuberculate; glands of the cyathia crescent-shaped, the horns slender, elongate, and caudate; [subgenus Esula, section Tithymalus].
............ ............ 13 Seeds tuberculate
............ ............ 13 Seeds finely pitted with numerous, evenly distributed, isodiametric pits.
............ ............ ..14 Dichasial bracts connate 1/4–1/2 of their length (often only on one side)
............ ............ ....15 Petioles 0-3 mm long; capsules ovoid-globose, 2.6-2.7 mm long; seeds with deep, rounded pits in 3-4 regular, vertical rows; [Interior Highlands of AR, e. OK, and s. MO; disjunct in c. TN]
............ ............ ....15 Petioles 2-5 mm long; capsules subglobose, 2-2.5 mm long; seeds with scattered, deep and broad pits; [TX]
............ ............ ..14 Dichasial bracts usually distinct, occasionally subconnate basally.
............ ............ ......16 Dichasial bracts strongly imbricate; seeds gray to purple-gray or sometimes nearly black
............ ............ ......16 Dichasial bracts not imbricate; seeds white to gray or red-brown to brown.
............ ............ ........17 Biennial or occasionally annual herbs; petioles of lower stem leaves 5-10 mm long; leaf blades usually oblanceolate to obovate, rarely ovate, 3-10 mm wide (at least some blades more than 5 mm wide); capsules 2.5-3.2 mm long.
............ ............ ........17 Annual herbs; petioles of lower stem leaves 0-2 mm long; leaf blades linear to oblanceolate, spatulate-cuneate, or slightly lanceolate, 0.5-5 mm wide; capsules 1.8-2.4 mm long.
............ ............ ..........18 Seeds reddish brown to brown, 1.3-1.4 × 0.8-0.9 mm, with 4-6 shallow pits or irregular oblong grooves on adaxial faces, small-pitted or nearly smooth on abaxial faces.
............ ............ ..........18 Seeds white to gray, 1.4-1.7 × 1-1.6 mm, with pits scattered over entire surface.
............ ............ ............ 19 Leaf blades oblanceolate, 3-5 mm wide; seeds ovoid, 1.6-1.7 × 1.4-1.6 mm; [granitic outcrops, GA].
............ ............ ............ 19 Leaf blades linear to slightly lanceolate or linear-oblanceolate, 0.5-2.5 mm wide; seeds ellipsoid, 1.4-1.7 × 1.0-1.3 mm; [sandy soils, TX Coastal Plain].
............ ............ ............ ..20 Stems 10-22 cm tall; leaf blades linear-oblanceolate, apices rounded; dichasial bracts reniform-ovate to subdeltate-ovate, bases truncate; seeds 1.6-1.7 × 1.1-1.3 mm, the surfaces with regular concave depressions; [Atascosa, Bexar, Wilson counties, TX].
............ ............ ............ ..20 Stems 6-13 cm tall; leaf blades linear to slightly lanceolate, apices acute; dichasial bracts broadly ovate-lanceolate, bases rounded; seeds 1.4-1.5 × 1-1.1 mm, the surfaces with irregular, not obviously concave depressions; [Jim Hogg, Kenedy counties, TX]

Key D: subgenus Euphorbia, section Nummulariopsis

1 Leaf blades < 6× as long as wide; leaves 5-32 mm wide.
..2 Involucres of cyathia 2.4-3.6 mm tall and wide; styles 3.3-3.6 mm long, connate ca. 1/2 their length; [Highlands county in c. peninsular FL]
..2 Involucres of cyathia 1.3-2.5 mm tall and wide; styles (1-) 1.3-1.5 mm long, connate ca. 1/4 their length; [FL Panhandle]
1 Leaf blades (5-) 7-20 (-50)× as long as wide; leaves 1.5-14 (-15) mm wide.
....3 Peduncles 2-5 mm long (except that of the 1st cyathium at the base of the pleiochasium) and not exceeding the dichasial bracts; seeds depressed-globose, wider than long
....3 Peduncles 6-24 mm long, often exceeding the dichasial bracts; seeds ovoid-globose, longer than wide.
......4 Leaf blades 1.5-3.5 (-4.5) mm wide, 15-20 (-50)× as long as wide; leaf apices short-acute to acuminate; [FL peninsula]
......4 Leaf blades (3-) 4-15 (-15) mm wide, 5-10 (-25)× as long as wide; leaf apices obtuse to short-acute; [ne. FL west to s. MS]