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Key to Asteraceae, Key A: woody composites (shrubs and lianas)

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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]  Clappia suaedifolia

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  Simsia calva

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

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 obovate to oblanceolate, unlobed, entire; heads (5-) 8-13 (-18+) mm in diameter; cypselas 3-4-smgled, not winged; [of tidally inundated salt and brackish marshes of the outer Coastal Plain, MD to s. FL, west to s. TX]  Borrichia

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

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

7 Disc flowers yellow to orange  Wedelia acapulcensis

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]  Iva

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].

Show caption*© Scott Ward                  9 Pappus of 4-10 scales, 0.3-7 mm long; [tribe Heliantheae; subtribe Chaenactidinae]  Palafoxia

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]  Garberia heterophylla

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  Chromolaena

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)]  Koanophyllon villosum

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]  Ageratina havanensis

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

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  Ampelaster carolinianus

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]  Medranoa palmeri

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]  Nipponanthemum nipponicum

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  Trixis inula

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]  Senecio riddellii

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  Medranoa palmeri

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]  Chrysoma pauciflosculosa

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  Gutierrezia

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

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  Artemisia

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

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  Baccharis

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  Bigelowia

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]  Brickellia dentata

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]  Pluchea carolinensis

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]  Garberia heterophylla

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]  Nahuatlea hypoleuca

Key to Asteraceae, Key B: herbaceous composites with opposite or whorled leaves
and discoid or disciform heads (lacking ray florets)

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Show caption*© Scott Ward, some rights reserved (CC BY), uploaded by Scott Ward 1 Pappus present, of 5-60 barbellate bristles; receptacle naked (without paleae or well-developed bristles); [tribe Heliantheae; subtribe Eupatoriae].

2 Plant a twining herb, phyllaries and disk florets 4 per head  Mikania

2 Plant stiffly erect to sprawling but never twining, phyllaries and disk florets usually > 4 per head.

3 Leaves in whorls of 3-7, > 2 cm wide  Eutrochium

3 Leaves opposite, rarely alternate or whorled, if whorled, < 2 cm wide.

4 Cypselae rostrate (with long beaks); the achene portion not bearing ribs  Chevreulia

4 Cypselae not beaked, the achene variously ribbed.

5 Achenes (and ovaries) 8-10-ribbed; outer phyllaries longitudinally striate  Brickellia

5 Achenes (and ovaries) (3-) 4-5-ribbed; outer phyllaries not noticeably longitudinally striate.

6 Heads pink to blue.

7 Phyllaries in 4-6+ series, deciduous  Chromolaena

7 Phyllaries in 2-4 series, persistent (or deciduous in Praxelis).

8 Heads pink (rarely bluish); receptacles flat; florets 18-25 per head; leaves sometimes gland-dotted  Fleischmannia incarnata

8 Heads blue; receptacles conic; florets 25-70 per head; leaves gland-dotted.

9 Bristles ca. 30; florets 35-70+; phyllaries ca. 25, subequal, persistent  Conoclinium

9 Bristles ca. 40; florets 25-30; phyllaries 15-25, unequal, deciduous (absence apparent in fruit)  Praxelis clematidea

6 Heads white to cream or, rarely, pale lilac.

10 Florets 3-7 per head  Eupatorium

10 Florets at least 9 per head.

11 Phyllaries not strongly imbricate, with the principal ones subequal and sub-biseriate; petioles 0.5-10 cm  Ageratina

11 Phyllaries clearly imbricate, in 3+ series, the margins usually glandular; some species epetiolate  Eupatorium

Show caption*© Scott Ward, some rights reserved (CC BY), uploaded by Scott Ward 1 Pappus either absent, or of scales, setae, or awns; receptacle naked, paleate, or bearing bristles.

12 Leaves whorled, linear, < 2 mm wide; head solitary; [aquatic herb growing in shallow stagnant water]  Sclerolepis uniflora

12 Leaves opposite (or alternate in part), broader in shape and > 5 mm wide; heads typically not solitary; [terrestrial or wetland plants].

Show caption*© Scott Ward                           13 Receptacle naked (epaleate).

Show caption*© Scott Ward                             14 Pappus of 2-12 scales; heads white, pink, or blue (yellow in Schkuhria).

15 Heads with 20-125 florets; leaves serrate or ± dentate (at least distally); [rarely naturalized exotics or s. TX/FL natives]; [tribe Eupatorieae].

16 Leaves petiolate; corolla tube glabrous, typically blue or lavender colored (sometimes white tinged); heads with 20-125 florets; [naturalized exotics or s. FL native]  Ageratum

16 Leaves sessile; corolla tube glandular-pubescent, typically white colored (sometimes pink-purple tinged); heads with 75-125 florets; [s. TX native]  Trichocoronis wrightii var. wrightii

15 Heads with 10-30 florets (or fewer in Schkuhria); leaves entire; [natives, of FL, s. GA, MS, and TX in our area]; [tribe Heliantheae; subtribe Chaenactidinae].

17 Leaves 3-5 lobed (or foliolate); cypselae with curled hairs (Florestina tripteris) or villous on angles (Schkuhria pinnata); [s. TX in our area or ne. waif].

18 Heads discoid, corolla white; cypselae with curled hairs; [s. TX in our area]  Florestina tripteris

18 Heads discoid, sometimes with 1 (-2) diminuitive rays, corolla (of discs) yellow; cypselae villous, at least at bases or on angles; [waif of ne US, native in sw. US]  Schkuhria pinnata

Show caption*© Scott Ward Show caption*© Scott Ward                                   17 Leaves simple or unlobed; cypselae with straight hairs; [variously distributed in s. GA and FL w. to MO and s. TX]  Palafoxia

14 Pappus none, or of a few bristles or irregular coroniform lobes; heads green to yellow.

19 Heads bright yellow, closely aggregated into corymbiform arrays of flat-topped to dome-shaped glomerules  Flaveria

19 Heads greenish or greenish yellow, borne in spiciform, racemiform, or paniculiform arrays.

20 Heads in paniculiform arrays, all or most of the heads not subtended by bracts  Cyclachaena xanthiifolia

20 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract  Iva

13 Receptacle with paleae or well-developed bristles.

21 Heads small, less than 1 cm in diameter at anthesis (the female heads enlarging in Xanthium); disc florets dull white or suffused with green or purple; florets mainly unisexual (either in the same heads and then males central and females peripheral, or in separate female and male heads); female florets 0-8 per head; [tribe Heliantheae; subtribe Ambrosiinae]

22 Heads unisexual; cypselas shed within an indurated bur or “nut” with hooked or straight spines developed from the phyllaries and/or paleae.

23 Involucre of the female heads with tubercles or straight spines developing from the phyllaries; burs 1-8 mm long  Ambrosia

23 Involucre of the female heads with hooked spines developing from the phyllaries/paleae; burs 10-35 mm long  Xanthium

22 Heads bisexual, with functionally male and female flowers in the same head; cypselas shed individually, not enclosed.

24 Heads in paniculiform arrays, all or most of the heads not subtended by bracts  Cyclachaena xanthiifolia

24 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract  Iva

21 Heads larger, mostly > 1 cm in diameter at anthesis; disc florets conspicuously white, yellow, pale yellow, or purple; florets mainly bisexual; female florets > 12 per head (except 2-8 in Polymnia and 8-15 in Verbesina occidentalis).

25 Leaves strongly basally disposed, the basal-most leaves sitting almost flat on the ground and overlapping; disc flowers maroon-purple  Helianthus radula

25 Leaves mainly or strictly cauline (not basally disposed); disc flowers white, yellow, or reddish-brown.

26 Disc flowers bright yellow or reddish-brown.

27 Involucre of phyllaries subtended by a calyculus of bracts obviously different in color, texture, and shape than the phyllaries.

Show caption*© Paul Marcum Show caption*© Alan M. Cressler                                                           28 Phyllaries usually distinct, rarely connate proximally; disk florets bright yellow  Bidens

28 Phyllaries connate (both proximally-distally connate); disk florets yellow to reddish-brown  Thelesperma

Show caption*© Jay Horn                                                         27 Involucre of phyllaries not subtended by a calyculus (phyllaries sometimes in 2+ series, but without obvious calyculi below).

29 Plants erect; heads without ray florets; [wet pine savannas and bogs; FL panhandle]  Verbesina chapmanii

29 Plants primarily prostrate or trailing, sometimes erect; heads with or without ray florets; [habitats various, widespread natives and non-natives]  Acmella

26 Disc flowers bright white or pale yellow.

30 Stems not winged; plants erect or spreading.

31 Cypselae 3-4 angled; pappus falling (of 2-12 awns or bristles); leaf margins irregularly crenate to serrate, the surfaces sometimes roughened but lacking glands; [e. of TX]  Melanthera

31 Cypselae 5-ribbed; pappus absent; leaf margins entire or serrulate, the surfaces gland-dotted; [s. TX]  Isocarpha oppositifolia var. achyranthes

Show caption*© Gary P. Fleming                                                               30 Stems winged; plants erect.

32 Disc flowers bright white; leaves unlobed or with 2 basal lobes  Verbesina occidentalis

32 Disc flowers creamy or pale yellow; leaves prominently pinnately lobed, with 5-many lobes  Polymnia