1 Leaves opposite, at least on the lower stem nodes (the leaves higher on the stem sometimes alternate); [tribe Heliantheae or tribe Eupatorieae].

..2 Heads radiate, the rays yellow to orange; disc flowers yellow to orange.

....3 Leaves linear; receptacle epaleate, but densely setose; [extreme s. TX]

....3 Leaves lanceolate or broader, 1-5× as long as wide; receptacle paleate; [collectively widespread].

......4 Leaves ovate, rhombic, or pentagonal, unlobed or 3-5-(-7) lobed; leaf blade margins toothed; leaves in part alternate upwards; [of disturbed, suburban areas of FL peninsula]; [tribe Heliantheae; subtribe Helianthinae]

........5 Ray laminae 5-16 mm long; leaf blades 7-33 cm long, the larger deeply 3-7-lobed; petiole bases dilated at base, fused to form a disc of leaf tissue at the stem

........5 Ray laminae 45-70 mm long; leaf blades 2-8 cm long, unlobed or 3-lobed; petiole bases not dilated at base

......4 Leaves lanceolate to oblanceolate, unlobed or obscurely 3-lobed; leaf blade margins toothed or entire; leaves strictly opposite; [tribe Heliantheae; subtribe Ecliptinae].

..........6 Leaves lanceolate, sometimes 3-lobed, usually serrate but sometimes nearly entire; heads 4-8 mm in diameter; cypselas flattened and winged; [TX only]

..2 Heads discoid or disciform (ray flowers lacking); disc flowers pink, purple, whitish, yellow, or orange.

............ 7 Disc flowers yellow to orange

............ 7 Disc flowers pink, purple, or white.

............ ..8 Heads small (involucres 2-8 mm high), solitary, axillary in the axils of leaves or leafy bracts (similar to the leaves but smaller) or interpretable as arrayed in bracteate racemes; heads nodding, the involucre 2-7 mm high; [collectively widespread in coastal portions of our area, of maritime situations]; [tribe Heliantheae; subtribe Ambrosiinae]

............ ..8 Heads small to larger (involucres 3-15+ mm high), many, terminal on the branches of corymbiform or paniculiform arrays; heads erect, the involucre 4-12 mm high; [of Coastal Plain of FL, s. GA, and TX].

............ ....9 Pappus of 4-10 scales, 0.3-7 mm long; [tribe Heliantheae; subtribe Chaenactidinae]

............ ....9 Pappus of 5-70 barbellate bristles, 3-12 mm long; [tribe Eupatoriae]

............ ......10 Leaf blades spatulate to obovate, cuneate to attenuate at the base, rounded or shallowly notched at the apex; leaf margins entire; leaves opposite below, alternate higher on the stems; [native of FL]

............ ......10 Leaf blades triangular or lanceolate, truncate, cordate, or cuneate at the base, acute to acuminate at the apex; leaf margins serrate; leaves opposite throughout.

............ ........11 Phyllaries broad, 2-3× as long as wide, the inner phyllaries translucent-scarious white to pinkish at their broadly rounded apices, falling as the head goes to fruit

............ ........11 Phyllaries narrow, 4-7× as long as wide, the inner phyllaries green at their acute to acuminate apices, persistent on the head in age.

............ ..........12 Involucres 2-3 mm in diameter; phyllaries 7-16 in 1-2 series; disc flowers 3-13 per head; [s. FL only (in our region)]

............ ..........12 Involucres 3-7 mm in diameter; phyllaries 25-35 in 2-3 series; disc flowers 10-60 per head; [TX only (in our region)].

............ ............ 13 Disc flowers white (to light pink); [c. TX]

............ ............ 13 Disc flowers blue to lavender (rarely white); [extreme s. TX]

1 Leaves strictly alternate.

............ ............ ..14 Heads radiate (with ray and disc flowers) or pseudoradiate (with pseudoradiate flowers only.

............ ............ ....15 Rays white, pink, or rose.

............ ............ ......16 Rays pink or rose, 30-50 (-70); sprawling viny shrub to 40 dm tall; leaves ovate, averaging ca. 3× as long as wide, with clasping base, with a midvein and lateral veins and tertiary reticulation

............ ............ ......16 Rays white, 5-34+; shrubs 2-30 dm tall; leaves either obovate to oblanceolate, averaging ca. 4× as long as wide, dentate, or linear, ca. 10× as long as wide, entire, cuneate.

............ ............ ........17 Rays white, 5-11 (-15); leaves linear, ca. 10× as long as wide, entire; [native, s. and se. TX]

............ ............ ........17 Rays white, 21-34+; leaves obovate to oblanceolate, averaging ca. 4× as long as wide, dentate; [non-native, known in our region only from NY]

............ ............ ....15 Rays or pseudorays yellow, orange-yellow, or light creamy yellow.

............ ............ ..........18 Heads pseudoradiate, with 11-25 pseudoray flowers and 0 disc flowers; leaves 8-70 mm wide

............ ............ ..........18 Heads radiate, with (0-) 1-11 (-15) ray flowers and 1-15 (-20) disc flowers; leaves (or their segments) 0.5-10 mm wide.

............ ............ ............ 19 Phyllaries in 1-2 series and equal or subequal in length to one another, the phyllaries often coherent/fused (the involucre thus appearing as a cylinder with ribs extending from base to top; calyculus (of bracts subtending the phyllaries and differing from them in texture, color, or orientation) present; [tribe Senecioneae]

............ ............ ............ 19 Phyllaries in 3-17 series and unequal in length (imbricated); calyculus absent.

............ ............ ............ ..20 Rays light creamy yellow, 5-11 (-15); involucre 3-5 (-7) mm in diameter

............ ............ ............ ..20 Rays bright yellow, (0-) 1-9; involucre 1-2.5 (-3) mm in diameter.

............ ............ ............ ....21 Pappus of 40-60 barbellate bristles; ray blades 4-6 mm long; leaf surfaces minutely pebbled; intricately branched shrubs to 1 m tall, with persistent sterile shoots with evergreen leaves and annual flowering shoots (the entire shoot and leaves deciduous); [Coastal Plain, se. NC south to Panhandle FL and s. MS]

............ ............ ............ ....21 Pappus absent, a low coroniform structure, or of scales; ray blades 2-3.5 mm long; leaf surfaces planar/revolute; shrubs 1-15 dm tall, not differentiated into evergreen, sterile shoots bearing deciduous, fertile shoots; [OK and TX westwards, very rarely as a waif eastwards].

............ ............ ............ ......22 Pappus of 5-10 elongate scales

............ ............ ............ ......22 Pappus absent or a low (< 0.1 mm high) crown

............ ............ ..14 Heads discoid (with disc flowers only).

............ ............ ............ ........23 Pappus absent; leaves 1-2× pinnately or 1× palmately lobed.

............ ............ ............ ..........24 Leaves either palmately 3-lobed, or pinnately lobed and the few (<11) lobes > 2 mm long

............ ............ ............ ..........24 Leaves 1-pinnately lobed, the many (>21) lobes mostly < 1.5 mm long and wide

............ ............ ............ ........23 Pappus of bristles; leaves unlobed (the margins entire or serrate).

............ ............ ............ ............ 25 Plants dioecious, either male or female; heads either staminate, with 10-50 flowers, or pistillate, with 20-150 flowers

............ ............ ............ ............ 25 Plants hermaphroditic; heads bisexual, with 5-25 flowers, either all perfect (bisexual), or a mixture of perfect (bisexual) and functionally staminate flowers.

............ ............ ............ ............ ..26 Leaves strongly basally disposed, crowded in the lowermost, woody or semiwoody portion of the stem

............ ............ ............ ............ ..26 Leaves on the stem.

............ ............ ............ ............ ....27 Leaves lanceolate to ovate (broadest below the midpoint); leaf margins entire to coarsely toothed.

............ ............ ............ ............ ......28 Heads in leafy, paniculate arrays; leaf blades coarsely dentate, 0.5-4 cm long; shrubs to 12 dm tall; [c. and e. TX]

............ ............ ............ ............ ......28 Heads borne in leafless, corymbiform arrays; leaf blades entire to denticulate, 5-16 (-20) cm long; shrubs to 40 dm tall; [FL and s. TX]

............ ............ ............ ............ ....27 Leaves obovate, spatulate, or orbiculate (with rounded apex) or elliptic (with acute to acuminate apex), broadest at or beyond the midpoint; leaf margins entire.

............ ............ ............ ............ ........29 Leaf blades obovate, spatulate, or orbiculate, rounded or slightly notched at the apex; leaf blade surfaces gray-green on both surfaces, granular when young; disc flowers 5 per head; [FL]

............ ............ ............ ............ ........29 Leaf blades elliptic, acute to acuminate at the apex; leaf blade strongly bicolored above and below, the upper surface dark green and glabrate, the lower surface densely and finely tomentose and strongly whitened, the upper surface dark green and glabrate or glabrous; disc flowers 4-25 per head; [s. TX]