1 Plant caulescent; leaf blades much longer than broad, base narrowly cuneate; peduncle/pedicel juncture articulated; bottom petal saccate at base, blade slightly to greatly exserted beyond lateral and upper petals.

  2 Leaves strictly alternate; leaf blades entire or with 1-2 random coarse teeth on either margin; corolla uniformly green; bottom petal < 1.3× as long as the others, blade slightly expanded, retuse; capsule 15-23 mm long; seeds 4.5-5.0 × 3.5-4.8 mm, subglobose, tan; [native, of nutrient-rich forests]

  2 Leaves strictly opposite, or upper leaves alternate and lower (sub)opposite; leaf blades entire, with few random crenations, or uniformly crenate or serrate; corolla white to violet or blue with yellow throat; bottom petal 1.5-3× as long as the others, blade somewhat to very much expanded, emarginate to broadly rounded; capsule < 10 mm long; seeds < 2 mm broad, flattened, black; [native of OK and TX westward, also as exotic waifs eastward]

1 Inflorescence an involucrate head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescences, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamens 5, the fruit a cypsela

1 Inflorescence, flower, and fruit structure various, but not with the combination of features as above (sometimes the flowers in a head subtended by bracts, e.g. Eryngium in APIACEAE, but then with other features differing, such as stamens 4, or green calyx present, or petals separate, or fruit a schizocarp of mericarps, etc.).

  2 Basal leaves 2-lobed, pinnately lobed, or palmately lobed (not considering cordate, hastate, or auriculate leaf bases as “lobed”).

    3 Basal leaves 2-lobed, hinged between the lobes, each lobe with stiff, marginal, eyelash-like bristles; [Coastal Plain of NC and SC, rarely planted and weakly naturalized elsewhere]

    3 Basal leaves 3-many-lobed, palmately or pinnately; [collectively widespread].

      4 Leaf lobing pinnate.

        5 Gynoecium of separate pistils (each with a single carpel); fruit an aggregate

        5 Gynoecium of a single pistil (with 2, rarely more, carpels); fruit simple.

          6 Stamens many; sepals 2, petals 4; fresh plants with yellow, orange, or white milky juice

          6 Stamens 4, 5, or 6; sepals 4 or 5; petals 4 or 5.

             7 Petals 4, distinct; stamens 6

             7 Petals 5, fused; stamens 2, 4, or 5.

               8 Corolla radially symmetrical; stamens 5

               8 Corolla 2-lipped, bilaterally symmetrical or asymmetrical; stamens 2 or 4.

                 9 Corolla lobes not twisted, the flower bilaterally symmetrical; stamens 2

                 9 Corolla lobes twisted so as to make the flower asymmetrical; stamens 4

      4 Leaf lobing palmate.

                   10 Petiole attachment peltate.

                     11 Leaves < 10 cm in diameter

                     11 Leaves > 15 cm in diameter

                   10 Petiole attachment marginal.

                       12 Ovary inferior.

                          13 Petals 4; stamens 8; fruit a capsule

                          13 Petals 5; stamens 5; fruit a schizocarp of 2 mericarps.

                            14 Fruit tuberculate; leaves 3-lobed

                            14 Fruit smooth; leaves with 5 or more lobes

                       12 Ovary superior, or half-inferior by fusion of a hypanthium a part of the way up the ovary wall.

                              15 Gynoecium of separate pistils (each with a single carpel); fruit an aggregate.

                                16 Perianth of 5 green sepals and 5 colored petals.

                                  17 Carpels partly fused, arrayed in a ring of 10-20

                                  17 Carpels separate, spiral, many

                                16 Perianth of a single whorl of 3-12 petaloid sepals (the petals absent or small and rudimentary).

                                    18 Leaves 2, the single flower terminal and associated with the upper leaf; fruit an aggregate of berries

                                    18 Leaves normally > 2, flowers not as above; fruit an aggregate of achenes, utricles, or follicles

                              15 Gynoecium of a single pistil (with 1-5 carpels); fruit simple.

                                       19 Hypanthium present, partially fused or not fused to the pistil; ovary partially inferior to superior

                                       19 Hypanthium absent; ovary superior.

                                         20 Petals connate at base; leaves sharply toothed

                                         20 Petals distinct; leaves with rounded lobes or teeth.

                                           21 Corolla radially symmetrical; petals 8-12; capsule fusiform, narrowed to both ends, > 5× as long as wide

  2 Basal leaves not lobed, at most serrate or crenate (and sometimes also cordate, hastate, auriculate, or peltate at the base).

                                             22 Basal leaves petiolate, the blade with a cordate, hastate, auriculate, or peltate base.

                                               23 Leaf margins entire.

                                                 24 Inflorescence a terminal and/or axillary raceme, panicle, or cyme of many small flowers; fruit an achene; perianth uniseriate, of 0, 4-5, or 6 tepals.

                                                    25 Flowers unisexual; staminate flowers 4-5 tepals, pistillate flowers lacking a perianth

                                                    25 Flowers bisexual; flowers with 6 tepals

                                                 24 Inflorescence either a terminal spike, or a 1-7-flowered terminal cyme, or of a solitary axillary or terminal flower; fruit various; perianth biseriate (of differentiated sepals and petals (except uniseriate, of 3 fused sepals in ARISTOLOCHIACEAE).

                                                      26 Flowers bilaterally symmetrical; inflorescence a terminal spike (with > 20 flowers); petals 4, usually scarious, transparent; sepals 4, green; stamens 4

                                                      26 Flowers radially symmetrical; inflorescence either of a solitary flower or of a 1-7-flowered terminal cyme; petals 5, 8-12, or 0; sepals 5 (green), 3 (brown), or 5-9 (yellow); stamens 5, 12, or many.

                                                        27 Gynoecium of separate pistils (each with a single carpel); fruit an aggregate of achenes or follicles; flowers bright yellow, either of 5-9 distinct petaloid sepals, or of 8-12 distinct petals subtended by 3-4 green distinct sepals

                                                        27 Gynoecium either of a single pistil with 6 carpels or of a single pistil with 4 carpels or of 2 nearly separate carpels; fruit a simple capsule (or deeply 2-lobed); flowers white, brown, or greenish, either of 5 fused or distinct white petals and 5 fused or distinct green sepals, or of 3 fused brown or greenish petaloid sepals.

                                                          28 Flowers brown or green, of 3 fused brown or greenish petaloid sepals (and 0 petals); carpels 6; stamens 12; leaves 4-10 cm wide

                                                          28 Flowers white, of 5 white or whitish petals and 5 green sepals; carpels 2; stamens 5; leaves 1-12 (-15) cm wide

                                                            29 Petals separate; sepals separate; plant glabrous

                                                            29 Petals fused (at least basally in Dichondra); sepals fused; carpels 2; plant pubescent.

                                                              30 Fruit a deeply 2-lobed capsule; sepals longer or ca. as long as petals; petals not undulate, fused at their bases or distal ½, the anthers maroon or brown-colored; [common, widespread in our area]

                                                              30 Fruit a fleshy berry; sepals shorter than the petals; petals undulate, fused, the anthers yellow; [rare exotic]

                                               23 Leaf margins crenate, serrate, or incised.

                                                                 31 Gynoecium of separate pistils (each with a single carpel); fruit an aggregate; perianth of 5 green sepals and 5 colored petals (or of 2 or 4 (-5) white-colored tepals in Begonia).

                                                                   32 Flowers typically with 2 or 4 (-5) white-colored tepals; leaf bases conspicuously oblique (sometimes variegated); fruit unequally or subequally 3-winged capsules; [ornamental waifs or uncommon non-natives]

                                                                   32 Flowers with 5 green sepals and 5 colored petals (not merged into tepals); leaf bases oblique or not; fruit various but not 3-winged capsules; [natives and non-natives].

                                                                     33 Carpels 10-20, partly fused, arrayed in a ring; petals white, pink, red, or purplish

                                                                     33 Carpels many, separate, spiral; petals yellow or white.

                                                                       34 Flowers lacking a hypanthium; fruit an aggregate of achenes or aggregate of follicles

                                                                       34 Flowers with a hypanthium; fruit an aggregate of drupelets or aggregate of achenes

                                                                 31 Gynoecium of a single pistil (with 1-5 carpels); fruit simple.

                                                                         35 Flowers radially symmetrical; inflorescence an umbel (or composite of umbelliform units, or a terminal panicle.

                                                                           36 Ovary superior; inflorescence a terminal panicle or terminal raceme.

                                                                              37 Inflorescence a terminal raceme; perianth of 4 green sepals and 4 white petals; fruit a silique/silicle; fresh foliage in spring and summer with a strong garlic odor; larger leaves < 10 cm in diameter

                                                                              37 Inflorescence a terminal panicle; perianth of 6 cream-colored petaloid sepals; fruit a winged achene; fresh foliage lacking a garlic odor; larger leaves typically > 30 cm in diameter

                                                                           36 Ovary inferior; inflorescence an umbel (or a composite of umbellate units); fruit a schizocarp of mericarps.

                                                                                38 Petiole attachment peltate

                                                                                38 Petiole attachment marginal (the blade cleft to the petiole.

                                                                                  39 Leaf blades longer than wide, sharply V-cleft at the base and otherwise shallowly denticulate

                                                                                  39 Leaf blades as broad or broader than long, cleft at the base and also irregularly serrate or crenate around the margin

                                             22 Basal leaves petiolate or not, with a truncate, rounded, or cuneate leaf base.

                                                                                    40 Leaves tubular, with a sutured ventral flange, erect or reclining, adapted as a pitfall for insects (flat, phyllodial leaves sometimes present as well, common in the winter in some species, such as S. oreophila)

                                                                                    40 Leaves flat, not sutured into a tubular shape.

                                                                                      41 Stem leaves opposite; perianth 5-merous, at least the corolla bilaterally symmetrical (barely so in VALERIANACEAE), or the parts curved so as to be asymmetrical (Pedicularis in OROBANCHACEAE); stamens 2, 3, or 4.

                                                                                        42 Ovary inferior; stamens 3

                                                                                        42 Ovary superior; stamens 2 or 4.

                                                                                           43 Corolla narrowly tubular, the five lobes flaring at nearly 90 degrees and nearly radially symmetrical

                                                                                           43 Corolla distinctly 2-lipped (with prominently large upper and lower corolla lobes) or hooded (the upper lip hood-like), distinctly bilaterally symmetrical, or the lobes twisted so as to make the corolla asymmetrical.

                                                                                             44 Corolla yellow, the upper lip often slightly to strongly maroon, hooded but the corolla lobes twisted so as to make the flower asymmetrical

                                                                                             44 Corolla white, lavender, or blue, 2-lipped and bilaterally symmetrical.

                                                                                               45 Sepals separate to the base or nearly so, not forming a tube

                                                                                               45 Sepals connate for at least 0.3× their length to form a tube

                                                                                      41 Stem leaves alternate; perianth radially symmetrical (less commonly bilaterally symmetrical); stamens 5, 6-8, 9, 10 (rarely 4).

                                                                                                 46 Ovary inferior (or half-inferior in Samolus).

                                                                                                   47 Perianth 4-merous; stamens 8

                                                                                                   47 Perianth 5-merous; stamens 5.

                                                                                                     48 Inflorescence an umbel; fruit a schizocarp of 2 mericarps

                                                                                                     48 Inflorescence an axillary or terminal raceme; fruit a capsule

                                                                                                 46 Ovary superior.

                                                                                                        49 Pistils many, each with a single carpel; fruit an aggregate of achenes

                                                                                                        49 Pistil 1, with 1-5 carpels; fruit simple (a legume, silique/silicle, capsule, utricle, or schizocarp of 4 nutlets).

                                                                                                          50 Corolla bilaterally symmetrical (barely so in Limosella in SCROPHULARIACEAE); stamens 2, 4, 6, 8, or 10.

                                                                                                            51 Stamens 6-8 or 10.

                                                                                                              52 Petals separate; stamens 10

                                                                                                              52 Petals fused; stamens 10 or 6-8.

                                                                                                                53 Stamens 10, monadelphous

                                                                                                                53 Stamens 6-8, epipetalous

                                                                                                            51 Stamens 2 or 4.

                                                                                                                  54 Stamens 2

                                                                                                                  54 Stamens 4.

                                                                                                                     55 [plants of coastal wetlands]

                                                                                                                     55 [plants of uplands or inland seeps or fens]

                                                                                                                       56 Flowers (and subtending bracts) red or yellow

                                                                                                                       56 Flowers purple, blue, or lavender

                                                                                                          50 Corolla radially symmetrical; stamens 5, 10, 4-6, or 9.

                                                                                                                         57 Perianth of 6 tepals; stamens 4-6 or 9; carpels 3

                                                                                                                         57 Perianth of green sepals and more brightly colored petals; stamens 5 or 10; carpels 2, 3, 4, or 5.

                                                                                                                           58 Leaves covered with sticky, gland-tipped hairs (often red), as flypaper traps for insects

                                                                                                                           58 Leaves lacking sticky gland-tipped hairs.

                                                                                                                             59 Fruit a schizocarp of 4 nutlets (ovary obviously 4-lobed in flower)

                                                                                                                             59 Fruit a capsule or silique/silicle (or utricle in Limonium in PLUMBAGINACEAE).

                                                                                                                               60 Inflorescence of a solitary, terminal flower; carpels 2-3 (-4).

                                                                                                                                  61 Corolla with a long tube and flaring corolla lobes (united > ½ its length)

                                                                                                                                  61 Corolla of separate petals or united only for a short length (< ¼ its length).

                                                                                                                                    62 Leaves serrate

                                                                                                                                    62 Leaves entire

                                                                                                                               60 Inflorescence of several to many flowers; carpels 5 (3 in Galax in DIAPENSIACEAE).

                                                                                                                                      63 Inflorescence an umbel; petals recurved, pink to almost white

                                                                                                                                      63 Inflorescence a raceme or panicle.

                                                                                                                                        64 Fruit a silique/silicle; petals 4; stamens 6

                                                                                                                                        64 Fruit either a capsule or a utricle; petals 5; stamens 5 or 10.

                                                                                                                                          65 Inflorescence a somewhat to very diffuse panicle, with 3 or more orders of branching, not giving at all the impression that the overall inflorescence is made of racemose units.

                                                                                                                                            66 Leaves entire; stamens 5; [plants of tidal marshes]

                                                                                                                                            66 Leaves serrate or crenate; stamens 10; [plants of various habitats, especially rock outcrops and bottomland forests and streambanks, never in tidal marshes]

                                                                                                                                          65 Inflorescence either a single terminal raceme (sometimes spike-like), or of 1 to several terminal and axillary racemes (these sometimes combined into a diffuse panicle, but one whose structure is clearly made up of many racemes).

                                                                                                                                               67 Inflorescence of 1-several terminal and axillary racemes, the plant typically well-branched, especially from the base; stamens 5

                                                                                                                                               67 Inflorescence of a single, terminal raceme, the plant unbranched; stamens 10 (or 5, with 5 staminodes)

                                                                                                                                                 68 Inflorescence spike-like, the flowers many (> 40), barely pedicelled; capsule 3-locular

                                                                                                                                                 68 Inflorescence a raceme, the flowers fewer (< 20) and distinctly pedicelled; capsule 5-locular