X
Jump to key:

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

Euphorbiaceae

Euphorbia

Copy permalink to share

1 Plants shrubs or subshrubs with succulent stems OR abundant stem spines; [subgenus Tirucalli OR subgenus Euphorbia (sections Crepidaria and Goniostema); FL].
  2 Plants bearing succulent stems only, without broadened leaves; [subgenus Tirucalli]
  2 Plants with broad leaves, not merely just long thin green succulent stems.
    3 Stems with abundant spines; [sect. Goniostema]
    3 Stems succulent, lacking abundant spines; [sect. Crepidaria].
      4 Stems zigzagged
      4 Stems straight
1 Plants herbaceous, lacking succulent or spiny stems; [subgenus Chamaesyce; Esula; Poinsettia; Euphorbia (sect. Nummulariopsis); widespread, including FL]
        5 Leaves strictly opposite, oblique or inequilateral at base; branches prostrate (less usually erect); [subgenus Chamaesyce; section Anisophyllum]
        5 Leaves alternate or opposite, not oblique or asymmetric at base; branches usually erect.
          6 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]
          6 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.
             7 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]
             7 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
               8 Ovary and capsule subtended by a calyx-like structure; seeds without caruncles; involucral gland appendages absent; [subgenus Euphorbia; section Nummulariopsis]
               8 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}

Copy permalink to share | Check for keys that lead to this key

1 Leaves serrulate, at least at the apex (use 10× magnification); seeds with 2-4 transverse ridges WHICH TAXA BELOW 1A have smooth seeds?
  2 Leaves and stems glabrous.
    3 Seeds with 3-4 (-6) prominent transverse ridges that interrupt abaxial keel; cyathia glands red to purple (sometimes yellow on older cyathia); stems prostrate; [s. IN and c. TN westward, primarily w. of MS river]
    3 Seeds with faint ridges, not interrupting abaxial keel; cyathia glands green, brown, or yellow to pink (lacking a darkened red or purple coloration).
      4 Stems erect to ascending (the tips not drooping)
      4 Stems prostrate to ascending, drooping at tips or plants mat-forming.
        5 Staminate flowers 2-5; seeds 0.9-1.0 mm long, minutely beaded with 3-4 transerve ridges that do not interrupt abaxial keel; [coastal LA and TX only]
        5 Staminate flowers 5-20; seeds 1.0-1.4 mm long, smooth, dimpled, or rugose; [scattered in our area, widespread in w. US]
  2 Leaves and stems variously pubescent.
          6 Ovaries and capsules glabrous.
             7 Stipules connate on both sides of stems.
               8 Stipules irregularly lacerate, ca. 0.5 mm long (sometimes to 1.0 mm); stems erect to ascending, the hairs (at least sparsely) pilose proximally and glabrous distally; seeds with 2-3 prominent transverse ridges, sometimes reticulate-pitted; [native SC s. to FL, w. through TX; waif northwards]
               8 Stipules triangular, or laciniate-subulate into filiform segments; stems prostrate or erect to ascending, the hairs usually spreading hirsute, strigillose or pilose (not just proximally); seeds rugulose, sometimes also bearing low transverse ridges; [VA w. to IL northward]
             7 Stipules distinct (or only basally connate on one side of the stem in E. nutans).
                 9 Leaf blade surfaces papillate, often also with at least some long thin hairs; cocci of capsule often elongated, distally empty; [TX]
                 9 Leaf blade surfaces not papillate, pilose, villous, sericeous, or glabrous; cocci of capsule not elongated nor distally empty; [collectively widespread].
                   10 Stipules usually distinct, sometimes connate on one side of stem; capsules 1.9-2.3 mm long; stems ascending or suberect, puberulent when young; adaxial surface of leaf blade often red-mottled; [widespread throughout our area]
                   10 Stipules distinct or connate (if connate, on both sides of stem); capsules 1.4-1.8 mm long; stems prostrate or widely spreading, spreading-hirsute [VA w. to IL northward]
          6 Ovaries and capsules variously pubescent.
                     11 Stipules connate (sometimes only on one side of the stem).
                       12 Stems erect to ascending.
                          13 Stipules usually distinct, rarely connate at base, if divided the segments deltate to linear-subulate; capsules and ovaries with whitish hairs; staminate flowers 2-8; seeds 0.7-0.9 mm long, usually rugulose or with 3-6 low transverse ridges; [widespread]
                          13 Stipules distinct when young, connate into a deltate scale when older, erose or laciniate with dark glands at the base or along the margins; capsules and ovaries with yellowish hairs; staminate flowers 15-25; seeds 1.2-1.3 mm long, with 3-5 shallow depressions separated by low, inconspicuous ridges; [c. and s. FL only]
                       12 Stems prostrate.
                            14 Capsules with conspicuous glabrous areas between pubescent keels.
                              15 Seeds smooth or with faint transverse ridges, reddish-brown, orange, or grayish-pink colored; plant pubescence variously sericeous, pilose, or villous; staminate flowers 6-15; [s. FL only]
                              15 Seeds with sharp transverse ridges, white with concealed brown color beneath the seed surface; plant pubescence crisped-villous; staminate flowers 3-6; [widespread, including s. FL]
                            14 Capsules uniformly pubescent, not with conspicuous glabrous areas between keels.
                                16 Styles unbranched
                                16 Styles 2-fid.
                                  17 Capsules strigose to sericeous; involucral gland appendages unequal; staminate flowers 3-5; [LA and FL]
                                  17 Capsules pilose to villous; involucral gland appendages ± equal in size (or absent); staminate flowers 8-12; [s. TX]
                     11 Stipules distinct.
                                    18 Styles unbranched
                                    18 Styles 2-fid.
                                       19 Capsules usually glabrous between pubescent keels (the pubescence most conspicuous only on the keels).
                                         20 Seeds smooth or with faint transverse ridges, reddish-brown, orange, or grayish-pink colored; plant pubescence variously sericeous, pilose, or villous; staminate flowers 6-15; [s. FL only]
                                         20 Seeds with sharp transverse ridges, white with concealed brown color beneath the seed surface; plant pubescence crisped-villous; staminate flowers 3-6; [widespread, including s. FL]
                                       19 Capsules uniformly pubescent, not with conspicuous glabrous areas between keels.
                                           21 Cyathia clustered, or in dichotomously branched axillary inflorescences. [THIS CHARACTER NEEDS VALIDATION OR RE-WORDING, TEST IN HERBARIUM]
                                             22 Gland appendages absent
                                             22 Gland appendages present (the petaloid portion of the cyathia, distal to the glands).
                                               23 Plants with coarse pubescence, the stem trichomes consisting of larger yellow and smaller white types; stipules usually distinct, rarely connate at base (if divided the segments deltate to linear-subulate); gland appendages sometimes absent or diminuitive; staminate flowers 2-8; seeds 0.7-0.9 mm long, usually rugulose or with 3-6 low transverse ridges; [widespread]
                                               23 Plants with fine pubescence, the stem trichomes only of one white type; stipules distinct when young, connate into a deltate scale when older, erose or laciniate with dark glands at the base or along the margins; gland appendages present; staminate flowers 15-25; seeds 1.2-1.3 mm long, with 3-5 shallow depressions separated by low, inconspicuous ridges; [c. and s. FL only]
                                           21 Cyathia solitary in the leaf axils, or in reduced unbranched axillary inflorescences. [THIS CHARACTER NEEDS VALIDATION OR RE-WORDING, TEST IN HERBARIUM]
                                                 24 Gland appendages (the petaloid portion of the cyathia) conspicuously unequal in length, at least one or two shorter than the remaining appendages; plants mat-forming (E. thymifolia) or not (only occasionally in E. pergamena); [FL].
                                                    25 Plants mat-forming, stems prostate only; glands elliptic; ovary densely strigose; staminate flowers 3-5; [disturbed uplands]
                                                    25 Plants not mat-forming (only occasionally in E. pergamena), stems prostate to ascending; glands lunate (crescent-shaped) or reniform (kidney-shaped); ovary puberulent, sericeous, or pilose; staminate flowers 5-15; [intact sites, occasionally disturbed].
                                                      26 Plants annual with taproots, the stems 10-45 cm long, pilose; leaves sometimes revolute; capsules pilose; seeds orange-brown, glaucous; staminate flowers 5-8; [pine rocklands, marl prairies, or disturbed uplands]
                                                      26 Plants perennial with thickened rootstocks, the stems 5-18 cm long, sericeous on upper surface and glabrous on lower surface; leaves not revolute; capsules puberulent, sericeous, or strigillose; seeds whitish to gray; staminate flowers 15; [pine rocklands]
                                                 24 Gland appendages ± equal in length; plants usually mat-forming; [collectively widespread, including FL].
                                                        27 Plants perennial with strongly thickened and lignified roostocks; staminate flowers 8-12; [s. TX only]
                                                        27 Plants annual with taproots (or sometimes taprooted perennials in E. thymifolia); staminate flowers 2-5; [collectively widespread in our area].
                                                          28 Middle nodes of stems forming adventitious roots (slowly pull up some of the stems to see if rooted in soil)
                                                          28 Stems not forming adventitious roots (stems merely lying flat).
                                                            29 Leaves serrulate (on the longer leaf margin) or subentire; seeds 1.0-1.2 mm long; styles clavate; [widespread]
                                                            29 Leaves (the larger ones at least) usually conspicuously serrate, smaller leaves serrulate; seeds 0.7-0.9 mm long; styles slender; [FL]
1 Leaves absolutely entire; seeds smooth, variously rugose or wrinkled, or bearing 2-4+ distinct transverse ridges.
                                                              30 Stems and leaves variously pubescent, at least on the upper stem surface (except E. deltoidea ssp. deltoidea, which can be pubescent to glabrous on both sides).
                                                                 31 Capsules with glabrous areas between the pubescent keels; plants annual; [s. TX]
                                                                 31 Capsules uniformly pubescent throughout (sparsely pubescent to glabrous in E. deltoidea ssp. deltoidea, but lacking the conspicuous contrast between keels and inter-keel space described above); plants perennial; [widespread, including TX].
                                                                   32 Distal leaves linear to elliptic-linear; [TX]
                                                                   32 Distal leaves not consistently and conspicuously linear (instead elliptic to ovate); [widespread, including TX]
                                                                     33 Stems erect to ascending.
                                                                       34 Stipules filiform; [OK and TX westward]
                                                                       34 Stipules triangular or subulate; [s. FL].
                                                                         35 Gland appendages unequal in length; stem pubescence limited to the upper surface (lower stem surface glabrous)
                                                                         35 Gland appendages ± equal in length; stem pubescence on both upper and lower stem surfaces.
                                                                           36 Stipules pilose; stems not wiry, 1-3 mm in diameter
                                                                           36 Stipules villous-hirsute; stems wiry, < 1 mm in diameter.
                                                                              37 Stem and capsule pubescence villous with uncinate or irregularly twisted hairs, 0.2-0.5 mm long
                                                                              37 Stem and capsule pubescence villous-hirsute with straight, spreading hairs, 0.6-0.7 mm long
                                                                     33 Stems prostrate or decumbent.
                                                                                38 Stipules filiform; [OK and TX westward]
                                                                                38 Stipules triangular or subulate; [s. FL or s. TX].
                                                                                  39 Capsules canescent; glands purple-black; the appendages absent or forming narrow rim around distal margin of gland; [s. TX]
                                                                                  39 Capsules glabrous or variously pubescent (canescent in E. deltoidea ssp. serpyllum); glands green to yellow-green or pinkish colored; the appendages either absent, forming a narrow ring, or present; [s. FL]
                                                                                    40 Gland appendages unequal in length; glands pinkish
                                                                                    40 Gland appendages ± equal in length; glands green to yellow-green.
                                                                                      41 Leaves and stems glabrous or sparsely pubescent
                                                                                      41 Leaves and stems canescent or villous.
                                                                                        42 Stem and capsule pubescence villous with uncinate or irregularly twisted hairs, 0.2-0.5 mm long
                                                                                        42 Stem and capsule pubescence canescent with appressed hairs, < 0.1 mm long
                                                              30 Stems and leaves glabrous (on both sides).
                                                                                           43 Stipules connate, forming a conspicuous scale-like structure; stems frequently rooting at the nodes.
                                                                                             44 Leaf margins whitish; plants perennial, with a moderately to strongly thickened rootstock; [TX westward]
                                                                                             44 Leaf margins green; plants annual, or sometimes perennial with a slightly thickened rootstock (E. blodgettii); [widespread, including TX].
                                                                                               45 Glands red, the appendages unequal in length; cyathia solitary, in cymose clusters distally on stem, or in congested axillary branches; [peninsular FL]
                                                                                               45 Glands yellow, the appendages uniformly equal in length; [widespread]
                                                                                           43 Stipules distinct, not merging to form a singular scale-like structure; stems rooting or not.
                                                                                                 46 Seeds 1.6-2.4 mm long; [OK and TX westward]
                                                                                                 46 Seeds 0.8-1.4 mm long; [collectively widespread].
                                                                                                   47 Cyathia solitary at distal nodes, the distal nodes not also bearing small cymose clusters.
                                                                                                     48 Stems prostrate, plants herbaceous, sometimes mat-forming.
                                                                                                        49 Leaf blades oblong to oblong-elliptic, 2.6-7.6 mm wide; involucral glands yellowish-pink, 0.3-0.5 mm long, the gland appendages 1.1-1.5 mm long; seeds 1.8-2.1 mm long
                                                                                                        49 Leaf blades narrowly elliptic to lanceolate, 1-2 mm wide; involucral glands slightly stipitate, ca. 0.1 mm long (rudimentary), the gland appendages 0.1-0.2 mm long; seeds 1.0-1.3 mm long
                                                                                                     48 Stems erect to ascending, plants herbaceous or subshrubs, not mat-forming.
                                                                                                          50 Plants subshrubs or small shrubs, conspicuously woody; [coastal habitats, FL]
                                                                                                          50 Plants herbaceous, sometimes slightly woody at base or with a thickened root stock but plants not obviously subshrubs or shrubs; [s. TX or s. FL]
                                                                                                            51 Leaf blade surfaces papillate, often also with at least some long thin hairs; cocci of capsule often elongated, distally empty; [s. TX]
                                                                                                            51 Leaf blade surfaces not papillate, usually glabrous or nearly so; cocci of capsule not elongated or distally empty; [s. FL].
                                                                                                              52 Leaves (2.2-) 3.0-6.0 (-8.3)× longer than wide, narrowly lanceolate to linear elliptic, 1-veined; [s. FL mainland only]
                                                                                                              52 Leaves 0.01–3.0 (-3.5)× longer than wide, ovate to lanceolate, 1–3-veined; [s. FL mainland or FL keys]
                                                                                                                53 Leaf apex acute; cyathia gland and appendage length 0.4-0.6 mm total; [FL keys only]
                                                                                                                53 Leaf apex obtuse to rounded; cyathia gland and appendage length 0.6-1.0 mm total; [s. FL mainland only]
                                                                                                   47 Cyathia solitary, or often in small cymose clusters at distal nodes.
                                                                                                                  54 Mature seeds bluntly 3-4 angled in cross-section, 0.9-1.4 (-1.7) mm long (except E. missurica, with seeds 1.5-2.0 mm long, but with leaves conspicuously linear); leaves fleshy or not.
                                                                                                                     55 Leaves linear (at least distally); seeds 1.5-2.0 mm long
                                                                                                                     55 Leaves oblong, ovate or elliptic; seeds 0.9-1.4 (-1.7) mm long.
                                                                                                                       56 Seeds gray to reddish brown, 0.9-1.1 mm long; leaf bases asymmetric but lacking expanded round auricle; [FL]
                                                                                                                       56 Seeds ashy white with a brown longitudinal line on adaxial surface, 1.1-1.4 (-1.7) mm long; leaf bases angled or rounded, with one side of the leaf base often expanded into a small rounded auricle; [s. IL to TX, westward]
                                                                                                                  54 Mature seeds rounded in cross section, (1.3-) 1.5-2.6 mm long; leaves often somewhat fleshy; [coastal only, barrier island dunes and other sandy coastal habitats].
                                                                                                                         57 Mature seeds (1.3-) 1.5-1.9 mm long; styles 0.2–0.3 mm; [preferring habitat behind foredunes, VA s. to FL, w. to TX]
                                                                                                                         57 Mature seeds (2.0-) 2.2-2.6 mm long; styles 0.7–1 mm; [preferring pioneer habitat in front of foredunes and along upper beach areas, FL Atlantic n. to Long Island in our area]

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

Copy permalink to share | Check for keys that lead to this key

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

Copy permalink to share | Check for keys that lead to this key

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; [ADD Euphorbia species 1].
               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 D: subgenus Euphorbia, section Nummulariopsis

Copy permalink to share | Check for keys that lead to this key

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]

Key to Euphorbia, Key E: subgenus Esula

Copy permalink to share | Check for keys that lead to this key

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); [subgenus Esula, section Lathyris]
             7 Stem leaves alternate (or mostly so); seeds 1-3 mm long.
               8 Leaves, pleiochasial bracts, and dichasial bracts of similar length throughout the plant; dichasial bracts alternate; pleiochasial branches 3-branched at nodes; cyathia glands lacking divergent, hornlike appendages; [coastal s. FL only]
               8 Leaves and bracts of dissimilar length, not uniform throughout the plant; dichasial bracts opposite; pleiochasial bracts unbranched or 2-branched at nodes; glands of the cyathia with or without hornlike appendages; [widespread, including FL]
                 9 Stem leaves linear to narrowly oblong, averaging ca. 10× as long as wide; [subgenus Esula, section Esula].
                   10 Stem leaves (5-) 10-30 mm long, 0.5-3 mm wide
                   10 Stem leaves 30-80 mm long, 3-8(-12) mm wide
                 9 Stem leaves oblanceolate, oblong, obovate, elliptic, or spatulate, averaging 1-5× as long as wide.
                     11 Seeds smooth, 3-5 mm (E. purpurea) or 1.4-1.6 mm long (E. helleri).
                       12 Primary stem leaves 6-15 mm long; plants taprooted annuals to 30 cm; ovaries glabrous; [LA and TX; section Tithymalus]
                       12 Primary stem leaves (50-) 70-100 cm long; plants robust rhizomatous perennials to 100+ cm tall; ovaries verrucose; [primarily Appalachian; section Helioscopia]
                     11 Seeds pitted or tuberculate, 1.3-2.0 mm long.
                          13 Seeds with one side pitted, the other with longitudinal grooves; [section Tithymalus].
                            14 Stem leaves obovate to suborbiculate, 4-15 mm wide; [widespread, non-native]
                            14 Stem leaves spatulate, 1-4 mm wide; [TX, native]
                          13 Seeds pitted on both faces.
                              15 Ovaries basally pilose; horns (of the glands) either short and blunt OR absent; seeds coarsely pitted with transversely elongate pits in 4 vertical rows; [section Pithyusa]
                              15 Ovaries glabrous; horns (of the glands) slender, elongate, and usually divergent; seeds finely and evenly pitted or tuberculate; [section Tithymalus].
                                16 Seeds tuberculate
                                16 Seeds finely pitted with numerous, evenly distributed, isodiametric pits.
                                  17 Dichasial bracts connate 1/4-1/2 of their length (often only on one side).
                                    18 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]
                                    18 Petioles 2-5 mm long; capsules subglobose, 2-2.5 mm long; seeds with scattered, deep and broad pits; [TX]
                                  17 Dichasial bracts usually distinct, occasionally subconnate basally.
                                       19 Dichasial bracts strongly imbricate; seeds gray to purple-gray or sometimes nearly black
                                       19 Dichasial bracts not imbricate; seeds white to gray or red-brown to brown.
                                         20 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.
                                         20 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.
                                           21 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.
                                           21 Seeds white to gray, 1.4-1.7 × 1-1.6 mm, with pits scattered over entire surface.
                                             22 Leaf blades oblanceolate, 3-5 mm wide; seeds ovoid, 1.6-1.7 × 1.4-1.6 mm; [granitic outcrops, GA].
                                             22 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].
                                               23 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].
                                               23 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]