VALERIANACEAE, the Valerian Family

Herbs with opposite leaves and small nearly or quite regular flowers; petals 5, united; stamens 3; sepals minute or wanting; ovary inferior.

1a. Stem-leaves pinnately cleft (3-10 dm. high; flowers white or pinkish, summer) — 2.
1b. Stem-leaves entire or dentate (2-6 dm. high; flowers white, summer) (Corn Salad) — 3.
2a. Leaf-segments parallel-veined Valerian, Valeriana edulis.
2b. Leaf-segments net-veined Swamp Valerian, Valeriana uliginosa.
3a. Upper stem-leaves entire Corn Salad, Valerianella chenopodifolia.
3b. Upper stem-leaves dentate Corn Salad, Valerianella radiata.


DIPSACACEAE, the Teasel Family

Herbs with opposite leaves, and small pale blue flowers aggregated in dense heads; calyx minute; petals 4, united; stamens 4, attached to the corolla; ovary inferior.

One species in Michigan, 1-2 m. high, with prickly leaves and stem, blooming in summer Teasel, Dipsacus sylvestris.


CUCURBITACEAE, the Gourd Family

Herbs, climbing by tendrils, with alternate palmately lobed leaves and imperfect flowers; staminate flowers in showy clusters, with 5-6 petals and 3 stamens; pistillate flowers small.

1a. Leaves 5-angled or shallowy 5-lobed (flowers white, summer) Bur Cucumber, Sicyos angulatus.
1b. Leaves 5-lobed to about the middle (commonly cultivated and frequently wild; flowers white, summer) Wild Cucumber, Echinocystis lobata.


CAMPANULACEAE, the Bellflower Family

Herbs with alternate simple leaves and milky juice; sepals 5; petals 5, united; stamens 5, attached at the very base of the corolla; ovary inferior.

1a. Stem-leaves circular or nearly so, cordate-clasping at base (2-6 dm. high; flowers blue, axillary, in summer) Venus' Looking-Glass, Specularia perfoliata.
1b. Stem-leaves linear or nearly so, not over 1 cm. wide (summer) — 2.
1c. Stem-leaves ovate to lanceolate, 2 cm. wide or more (flowers blue, in a terminal spike or raceme, summer) (Bellflower) — 4.
2a. Stem and leaves glabrous (or rarely pubescent) (1-6 dm. high; flowers blue) Harebell, Campanula rotundifolia.
2b. Stem and leaves rough with reflexed bristles (marsh plants, with weak slender stems 3-10 dm. long; flowers white or pale-blue) (Marsh Bellflower) — 3.
3a. Corolla 5-8 mm. long Marsh Bellflower, Campanula aparinoides.
3b. Corolla 10-12 mm. long Marsh Bellflower, Campanula uliginosa.
4a. Corolla rotate; flowers in spikes (6-15 dm. high) Bellflower, Campanula americana.
4b. Corolla bell-shape; flowers in one-sided racemes (4-10 dm. high) Bellflower, Campanula rapunculoides.


LOBELIACEAE, the Lobelia Family

Herbs with alternate simple leaves and milky juice; flowers irregular; petals 5, united; corolla split down the upper side; stamens 5, united by their anthers into a ring or tube surrounding the style; ovary 2-celled, inferior. Flowers in summer and autumn.

1a. Leaves all basal, tubular; flowers on leafless stalks (aquatic, 1-4 dm. high; flowers blue) Water Lobelia, Lobelia dortmanna.
1b. Leaves normal, on the stem — 2.
2a. Flowers more than 2 cm. long (5-10 dm. high) — 3.
2b. Flowers about 1 cm. long, or shorter (flowers light blue) — 4.
3a. Flowers scarlet Cardinal Flower, Lobelia cardinalis.
3b. Flowers blue Great Lobelia, Lobelia siphilitica.
4a. Flowers in loose racemes, pedicelled — 5.
4b. Flowers in slender terminal spike-like racemes, nearly sessile (4-10 dm. high, usually unbranched) Lobelia, Lobelia spicata.
5a. Foliage pubescent (3-8 dm. high) Indian Tobacco, Lobelia inflata.
5b. Foliage glabrous (1-4 dm. high) Lobelia, Lobelia kalmii.


COMPOSITAE, the Composite Family

Herbs, with various types of foliage, but with flowers of characteristic structure, resembling a sunflower, a thistle, or a dandelion. Each apparent flower is a head of numerous small flowers, attached side by side to the expanded end of the stem, and subtended and partly enclosed by a series of bracts, called the involucre, which resembles a calyx.

The calyx of the individual flower is minute or actually wanting, and is usually modified to aid in seed dispersal. It appears at the base of the corolla, at the summit of the inferior ovary, and is known as pappus. The structure of the pappus is best observed in the ripe fruit.

The corolla of the individual flowers consists of 5 (or rarely 4) united petals. In some flowers the petals are united to form a tubular or bell-shape corolla. In others they are united to form a flat or strap-shape corolla. The stamens are attached to the corolla, and are united by their anthers into a tube which surrounds the style, and above which the 2-lobed stigma protrudes.

The apparent flower of a Composite, composed of several or many individual flowers, is termed a head. It may be composed entirely of tubular flowers, as the thistle or bone-set; or entirely of strap-shape flowers, as the dandelion; or of both sorts together, as the aster or sunflower. In the latter case, the tubular flowers invariably occupy the center of the head, called the disk, and the larger strap-shape flowers are at the margin, where their projecting corollas, called rays, may be very conspicuous. Such heads are called radiate.

In a few composites (see 1a below) the flowers have minute corollas without colored parts.

In identifying a composite, determine first whether the heads are composed of tubular flowers, of strap-shape flowers, or of both sorts together; and, secondly, observe the nature of the pappus, using preferably the ripe heads, or at least the oldest flower-heads available. No further difficulties will be encountered.

1a. Flowers without petal-like or brightly colored parts; staminate and pistillate flowers in separate heads (or rarely in the same heads); coarse weeds with inconspicuous flowers (summer and autumn) — 2.
1b. Flowers with some petal-like parts, usually brightly colored or white — 10.
2a. Leaves toothed or lobed — 3.
2b. Leaves deeply pinnatifid or dissected (4-15 dm. high; flowers in erect spikes) (Ragweed) — 7.
3a. Fruit or pistillate flowers thickly covered with sharp hooked spines (3-10 dm. high) (Cocklebur) — 4.
3b. Fruit not spiny — 8.
4a. With spines on the stem at the base of the leaves Cocklebur, Xanthium spinosum.
4b. Without any spines on the stem — 5.
5a. Body of the bur smooth or slightly hairy Cocklebur, Xanthium canadense.
5b. Body of the bur and the spines densely pubescent — 6.
6a. Body of the bur more than twice as long as thick; a common weed Cocklebur, Xanthium commune.
6b. Body of the bur less than twice as long as thick Cocklebur, Xanthium echinatum.
7a. Leaves twice-pinnatifid Ragweed, Ambrosia artemisiifolia.
7b. Leaves once-pinnatifid Ragweed, Ambrosia psilostachya.
8a. Leaves deeply 3-lobed (1-5 m. high) Giant Ragweed, Ambrosia trifida.
8b. Leaves serrate or obscurely lobed — 9.
9a. Stem simple or sparingly branched; pistillate heads in the axils of the upper leaves (1-3 m. high) Giant Ragweed, Ambrosia trifida var. integrifolia.
9b. Stem much branched; heads all alike, in panicles Marsh Elder, Iva xanthifolia.
10a. Flowers all strap-shape; juicy milky. (The central flowers must be examined carefully, since they are frequently much smaller than the marginal ones) — 11.
10b. Flowers all tubular, with regular. 4-5-lobed corollas — 45.
10c. Flowers both tubular and strap-shape; heads radiate (in a few species the rays are small and may be overlooked by mistake) — 108.
11a. Flowers blue (summer and autumn) — 12.  
11b. Flowers orange, yellow, white, or purplish — 15.
12a. Heads 2.5 cm. wide, or larger — 13.
12b. Heads 1.5 cm. wide, or smaller — 14.
13a. Leaves linear; bracts longer than the flowers, heads 5-10 cm. wide (6-15 dm. high) Salsify, Tragopogon porrifolius.
13b. Leaves broader, mostly serrate; bracts shorter than the flowers; heads 2.5-4 cm. wide Chicory, Cichorium intybus.
14a. Heads in a narrow crowded cluster (5-15 dm. high) — 30b.
14b. Heads in a spreading open panicle (Wild Lettuce) — 22.
15a. Heads solitary at the summit of leafless stalks — 16.
15b. Heads several, on leafy, naked, or scaly stalks — 19.
16a. Basal leaves strictly entire; heads about 2.5 cm. wide (summer and autumn) — 35a.
16b. Basal leaves toothed, lobed, or pinnatifid (spring and summer) — 17.
17a. Heads 8-14 mm. wide (1-4 dm. high) Dwarf Dandelion, Krigia virginica.
17b. Heads 25-50 mm. wide (1-6 dm. high) (Dandelion) — 18.
18a. Outer involucral bracts reflexed Dandelion, Taraxacum officinale.
18b. Outer involucral bracts erect or spreading Dandelion, Taraxacum erythrospermum.
19a. Pappus none; heads about 1 cm. wide (4-10 dm. high; summer) Nipplewort, Lapsana communis.
19b. Pappus of an inner row of bristles and an outer row of short scales; heads about 3 cm. wide (3-8 dm. high; early summer) Cynthia, Krigia amplexicaulis.
19c. Pappus of feathery bristles (summer) — 20.
19d. Pappus of simple bristles — 25.
20a. Flower-stalk scaly, without foliage leaves (2-6 dm. high) Fall Dandelion, Leontodon autumnalis.
20b. Stem leafy (3-10 dm. high) — 21.
21a. Leaves entire, linear-lanceolate Meadow Salsify, Tragopogon pratensis.
21b. Leaves serrate, oblong-lanceolate Picris, Picris hieracioides.
22a. Pappus tawny in color (1-3 m. high) — 23.
22b. Pappus white — 24.
23a. Leaves pinnatifid Wild Lettuce, Lactuca spicata.
23b. Leaves undivided, dentate Wild Lettuce, Lactuca spicata var. integrifolia.
24a. Upper leaves entire; heads about 1.5 cm. wide (5-10 dm. high) Wild Lettuce, Lactuca pulchella.
24b. Upper leaves dentate or lobed; heads about 1 cm. wide (1-3 m. high) Wild Lettuce, Lactuca floridana.
25a. Achene tipped with a slender beak, bearing the pappus at its summit (summer) (Wild Lettuce) — 26.  
25b. Achene without a beak — 29.
26a. Leaves hirsute or hispid on the mid-veins beneath — 27.
26b. Leaves glabrous — 28.
27a. Leaves pubescent on both sides (1-2 m. high) Wild Lettuce, Lactuca hirsuta.
27b. Leaves glabrous, except on the mid-vein (5-15 dm. high) Wild Lettuce, Lactuca scariola var. integrata.
28a. Leaves entire or sparsely toothed (1-2 m. high) Wild Lettuce, Lactuca sagittifolia.
28b. Leaves chiefly sinuate-pinnatifid (1-3 m. high) Wild Lettuce, Lactuca canadensis.
29a. Flowers white, cream-color, or purplish (summer and autumn) (Rattlesnake Root) — 30.
29b. Flowers bright-yellow or orange — 33.
30a. Heads nodding (6-20 dm. high) — 31.
30b. Heads pointing in various directions, in spike-like panicles; involucres pubescent (5-15 dm. high) Rattlesnake Root, Prenanthes racemosus.
31a. Heads with 5-7 flowers in each Rattlesnake Root, Prenanthes altissima.
31b. Heads with 8-12 flowers — 32.
31c. Heads with 20 or more flowers Rattlesnake Root, Prenanthes crepidinea.
32a. Pappus dark reddish-brown Rattlesnake Root, Prenanthes alba.
32b. Pappus pale-brown or nearly white Rattlesnake Root, Prenanthes trifoliata.
33a. Pappus tawny or brown in color (summer and autumn) (Hawkweed) — 34.
33b. Pappus white — 42.
34a. Heads 2.5 cm. in diameter, or larger — 35.
34b. Heads 1-2 cm. in diameter (4-10 dm. high) — 37.
35a. Leaves all basal (1-4 dm. high) Hawkweed, Hieracium pilosella.
35b. Stem-leaves present (4-15 dm. high) — 36.
36a. Leaves rounded at the sessile base Hawkweed, Hieracium canadense.
36b. Leaves narrowed toward the base Hawkweed, Hieracium umbellatum.
37a. A rosette of basal leaves conspicuous at flowering time — 38.
37b. No rosette of basal leaves at time of flowering — 41.
38a. Leaves glabrous on the upper side — 39.
38b. Leaves hairy on the upper side — 40.
39a. Stem glabrous, leafless or with one or two leaves Hawkweed, Hieracium venosum.
39b. Stem with several leaves, hairy below Hawkweed, Hieracium marianum.
40a. Leaves with short scattered hairs above Hawkweed, Hieracium gronovii.
40b. Leaves and stem densely covered with very long hairs Hawkweed, Hieracium longipilum.
41a. Leaves glabrous Hawkweed, Hieracium paniculatum.
41b. Leaves very hairy Hawkweed, Hieracium scabrum.
42a. Bracts of the involucre smooth (5-20 dm. tall; summer and autumn) (Sow Thistle) — 43.
42b. Bracts of the involucre hairy — 44.
43a. The clasping leaf-bases acute Sow Thistle, Sonchus oleraceus.
43b. The clasping leaf-bases rounded Sow Thistle, Sonchus asper.
44a. Heads 2.5-5 cm. broad; involucre 2 cm. long (4-10 dm. high) Sow Thistle, Sonchus arvensis.
44b. Heads 1-2 cm. broad; involucre 6-10 mm. long (3-6 dm. high; summer) Hawksbeard, Crepis tectorum.
45a. Leaves or involucre or both spiny (thistles, burdock, etc.) — 46.
45b. Neither leaves nor involucre spiny — 60.
46a. Leaves 1-4 dm. broad, not spiny (flowers purple or white; summer) (Burdock) — 47.
46b. Leaves narrower, not spiny — 48.
47a. Diameter of involucre at flowering time 3-5 cm. (1-3 m. high) Burdock, Arctium lappa.
47b. Diameter of involucre at flowering time 1.5-3 cm. (5-15 dm. high) Burdock, Arctium minus.
48a. Each head 1-flowered; heads aggregated in a globular head-like cluster (1-2 m. high; flowers blue or white, summer) Globe Thistle, Echinops sphaerocephalus.
48b. Each head many-flowered — 49.
49a. Principal involucral bracts with stout spreading spines 2-4 cm. long (5-15 dm. high; flowers purple, summer) Milk Thistle, Silybum marianum.
49b. Principal involucral bracts with slender spines or none — 50.
50a. Pappus feathery; receptacle bristly (summer and autumn) (Thistle) — 51.
50b. Pappus not feathery (flowers purple, summer) — 59.
51a. Heads subtended by a circle of large leafy bracts (5-15 dm. high; flowers pale-yellow) Thistle, Cisium spinoissimum.
51b. Heads not subtended by several leafy bracts — 52.
52a. Leaves conspicuously white-woolly on both sides (4-10 dm. high) — 53.
52b. Leaves conspicuously white-woolly or brown-woolly below, not above (flowers purple or pink) — 54.
52c. Leaves green on both sides (flowers pink or purple, rarely white) — 56.
53a. Leaves deeply pinnately parted with linear divisions; flowers almost white Thistle, Cirsium pitcheri.
53b. Leaves irregularly pinnatifid; flowers purple-pink Thistle, Cirsium undulatum.
54a. Stem-leaves entire or shallowly lobed (1-3 m. high) Thistle, Cirsium altissimum.
54b. Stem-leaves obviously pinnatifid (1-2 m. high) — 55.
55a. Leaves decurrent on the stem Thistle, Cirsium lanceolatum.
55b. Leaves not decurrent Thistle, Cirsium discolor.
56a. Outer and middle involucral bracts appressed, pointless or with weak short prickles — 57.
56b. Outer and middle bracts erect, not appressed, acuminate into a long slender more or less prickly tip (4-10 dm. high) — 58.
57a. Heads numerous 2-2.5 cm. broad, in close clusters (5-12 dm. high) Canada Thistle, Cirsium arvense.
57b. Heads few or solitary, 3-5 cm. broad (1-2 m. high) Thistle, Cirsium muticum.
58a. Principal bracts with a conspicuous viscid stripe down the middle; heads 6-19 cm. broad, solitary or few Thistle, Cirsium hillii.
58b. Principal bracts not viscid Thistle, Cirsium pumilum.
59a. Receptacle not bristly; heads 3-5 cm. wide (1-3 m. high; flowers pale-purple, summer) Cotton Thistle, Onopordum acanthium.
59b. Receptacle bristly; heads 2-2.5 cm. wide (5-12 dm. high; flowers purple to white, late summer) Thistle, Carduus crispus.
60a. Leaves basal; stem-leaves none or reduced to scales (2-8 dm. high; flowers whitish, in spring) — 61.
60b. Stem-leaves present; basal leaves present or absent — 62.
61a. Leaves toothed or lobed; flower-stalk not scaly Adenocaulon, Adenocaulon bicolor.
61b. Leaves deeply cleft; flower-stalk scaly — 197a.
62a. Leaves compound or dissected (flowers in summer and autumn) — 63.
62b. Leaves merely lobed, never truly compound or dissected — 72.
62c. Leaves entire or serrate — 78.
63a. Some of the involucral bracts leaf-like, longer than the heads (3-20 dm. high; flowers yellow or greenish, summer and autumn) (Beggar Ticks) — 126.
63b. Bracts short and not leaf-like — 64.
64a. Heads 7-20 mm. wide, in a flat-topped or convex cluster (3-10 dm. high; flowers yellow, summer) (Tansy) — 65.
64b. Heads smaller, in spikes, racemes, or panicles (flowers yellow or greenish, late summer and autumn) (Wormwood) — 66.
65a. Heads 7-10 mm. wide, numerous in a dense cluster Tansy, Tanacetum vulgare.
65b. Heads 10-20 mm. wide, few, 2-10 in a loose open cluster Tansy, Tanacetum huronense.
66a. Heads 2-3 mm. broad (4-15 dm. high) — 67.
66b. Heads 4-6 mm. broad (3-10 dm. high) — 69.
67a. Leaf-lobes narrowly linear, strictly entire Wormwood, Artemisia caudata.
67b. Leaf-lobes serrate — 68.
68a. Heads in a loose spreading panicle Wormwood, Artemisia annua.
68b. Heads in axillary clusters, producing a leafy spike-like panicle Wormwood, Artemisia biennis.
69a. Leaf-lobes narrowly linear — 70.
69b. Leaf-lobes oblong to obovate, not linear — 71.
70a. Shrubby; involucre pubescent Southernwood, Artemisia abrotanum.
70b. Herbaceous; involucre glabrous or rarely pubescent Wormwood, Artemisia canadensis.
71a. Leaves finely gray-pubescent on both sides Wormwood, Artemisia absinthium.
71b. Leaves smooth or nearly so above, densely white-woolly beneath Mugwort, Artemisia vulgaris.
72a. Heads 2-4 cm. broad, purple, blue, or rarely white (3-6 dm. high; summer) — 92.
72b. Heads 1 cm. wide or less — 73.
73a. Leaves densely white-woolly beneath (flowers yellowish, late summer) — 74.
73b. Leaves smooth or hairy, never white-woolly — 75.
74a. Heads 6-8 mm. wide (4-8 dm. high) Wormwood, Artemisia stelleriana.
74b. Heads 3-4 mm. wide (5-10 dm. high) Wormwood, Artemisia ludoviciana.
75a. Principal bracts of the involucre 5, with frequently a few much smaller ones — 76.
75b. Principal bracts of the involucre numerous — 77.
76a. Heads few in small terminal clusters; foliage somewhat viscid-pubescent (6-15 dm. high; flowers yellow, summer) — 114a.
76b. Heads very numerous in flat-topped clusters; foliage never viscid-pubescent (1-2 m. high; flowers white, late summer) — 105c.
77a. Leaves broadly halberd-shape, 3-lobed (1-2 m. high; flowers white, late summer) — 105b.  
77b. Leaves lobed only at the base (5-10 dm. high; flowers yellow, summer) — 93a.
77c. Leaves pinnatifid (2-8 dm. high; flowers yellow) — 172.
78a. Bracts of the involucre dry and chaffy, at least at the tip; plants always pubescent and usually white-woolly — 79.
78b. Bracts of the involucre green or colored, but never dry and chaffy — 90.
79a. Pappus none; heads 3-4 mm. wide, in ample panicled spikes (flowers yellowish, late summer) — 74b.
79b. Pappus a minute ring or crown; leaves crenate (5-10 dm. high; flowers yellow, summer) — 93a.
79c. Pappus of hairs; heads in flat-topped clusters or slender spikes — 80.
80a. Heads sessile or subsessile in small flat-topped clusters; flowering in spring or early summer; principal leaves basal (1-4 dm. high; flowers white or purplish) (Everlasting) — 81.
80b. Heads in terminal spikes (2-6 dm. high; flowers purplish, summer) Cudweed, Gnaphalium purpureum.
80c. Heads in small or large flat-topped clusters, flowering in summer or autumn; principal leaves on the stem — 88.
81a. Stolons from the basal rosette of leaves leafy throughout and ascending at the tip — 82.
81b. Stolons prostrate throughout, leafy only at the tip — 87.
82a. Basal leaves 2-5 cm. long, 1-nerved — 83.
82b. Basal leaves 5-12 cm. long, 3-nerved — 84.
83a. Basal leaves spatulate or oblanceolate, smooth above Everlasting, Antennaria canadensis.
83b. Basal leaves obovate, pubescent above Everlasting, Antennaria neodioica.
84a. Basal leaves smooth above Everlasting, Antennaria parlinii.
84b. Basal leaves dull green and pubescent above — 85.
85a. Heads 6-8 mm. high Everlasting, Antennaria plantaginifolia.
85b. Heads 8-11 mm. high — 86.
86a. Leaf-blade ovate or obovate Everlasting, Antennaria fallax.
86b. Leaf-blade spatulate, with rounded tip Everlasting, Antennaria occidentalis.
87a. Styles crimson Everlasting, Antennaria neglecta.
87b. Styles pale yellow Everlasting, Antennaria petaloidea.
88a. Erect; involucral bracts pearly white (4-9 dm. high) Pearly Everlasting, Anaphalis margaritacea.
88b. Erect; involucral bracts dull white or pale brown, somewhat pubescent (4-8 dm. high) (Cudweed) — 89.
88c. Diffusely branched; heads in dense clusters; bracts brown (1-2 dm. high) Cudweed, Gnaphalium uliginosum.
89a. Leaves decurrent on the stem Cudweed, Gnaphalium decurrens.
89b. Leaves not decurrent on the stem Cudweed, Gnaphalium polycephalum.
90a. Twining vine (flowers white, summer) Hemp Weed, Mikania scandens.
90b. Not twining or climbing — 91.
91a. Involucral bracts deeply fringed at the tip (flowers purple, blue, or rarely white, summer; 3-6 dm. high) — 92.
91b. Involucral bracts entire or nearly so — 93.
92a. Upper leaves linear or narrowly lanceolate Corn Flower, Centaurea cyanus.
92b. Upper leaves oblong or oblong-lanceolate Knapweed, Centaurea nigra.
93a. Pappus none or a short ring or crown (5-10 dm. high; flowers yellow, summer) Costmary, Chrysanthemum balsamita var. tanacetoides.
93b. Pappus of 2-4 stiff awns (2-15 dm. high; flowers yellow, late summer) (Bur Marigold) — 130.
93c. Pappus of hairs or bristles — 94.
94a. Leaves linear or narrowly lanceolate, entire; heads never in a large flat-topped cluster — 95.
94b. Leaves not linear — 99.
95a. Heads showy, purple, in a long spike or raceme (late summer) (Blazing Star) — 96.
95b. Heads not showy, in a loose panicle or raceme — 240b.
96a. Involucral bracts rounded at the tip, appressed (5-15 dm. high) — 97.
96b. Involucral bracts pointed (3-6 dm. high) — 98.
97a. Heads 8-12-flowered Blazing Star, Liatris spicata.
97b. Heads with 25 flowers or more Blazing Star, Liatris scariosa.
98a. Involucral bracts long-acuminate, spreading Blazing Star, Liatris squarrosa.
98b. Involucral bracts mucronate, appressed Blazing Star, Liatris cylindracea.
99a. Flowers yellow (2-8 dm. high) — 172b.
99b. Flowers bright-red or purple, in flat-topped clusters (8-20 dm. high; late summer) (Ironweed) — 100.
99c. Flowers blue (3-8 dm. high; late summer) Mist Flower, Eupatorium coelestinum.
99d. Flowers flesh-color, pink, cream-color, or white (flowers in summer) — 103.
100a. Leaves glabrous beneath or minutely pubescent; heads 15-30-flowered — 101.
100b. Leaves tomentose beneath; heads 30-50-flowered — 102.
101a. Inflorescence densely crowded; usually 1 m. or less high Ironweed, Vernonia fasciculate.
101b. Inflorescence loose and open, 15-30 cm. wide; 1-2 m. high Ironweed, Vernonia altissima.
102a. Pappus tawny in color Ironweed, Vernonia missurica.
102b. Pappus purple Ironweed, Vernonia illinoensis.
103a. Leaves alternate — 104.
103b. Leaves opposite — 106.
103c. Leaves whorled (1-3 m. high; flowers pink or purple, late summer) (Joe-Pye Weed) — 107.
104a. Heads 5-flowered (5-20 dm. high; flowers white or pinkish, late summer) (Indian Plantain) — 105.
104b. Heads 10 25-flowered (5-10 dm. high; flowers white, late summer) False Boneset, Kuhnia eupatorioides.
104c. Heads with more than 50 flowers (3-20 dm. high; flowers white, summer) Fireweed, Erechtites hieracifolia.
105a. Leaves entire, with many veins from base to apex Indian Plantain, Cacalia tuberosa.
105b. Leaves sharply serrate Indian Plantain, Cacalia suaveolens.
105c. Leaves broadly triangular or kidney-shape, sinuate or entire Indian Plantain, Cacalia atriplicifolia.
106a. Leaves united at the base (5-15 dm. high) Boneset, Eupatorium perfoliatum.
106b. Leaves sessile but not united at the base (5-15 dm. high) Upland Boneset, Eupatorium sessilifolium.
106c. Leaves petioled (4-12 dm. high) White Snakeroot, Eupatorium urticaefolium.
107a. Inflorescence ovoid or pyramidal Joe-Pye Weed, Eupatorium purpureum.
107b. Inflorescence depressed or flattened Joe-Pye Weed, Eupatorium purpureum var. maculatum.
108a. Rays yellow or brown — 109.
108b. Rays white to blue or red, never yellow or brown — 197.
109a. Principal leaves basal, the stem merely with bract-like scales — 110.
109b. Principal leaves on the stem, opposite or whorled — 111.
109c. Principal leaves on the stem, alternate, or with smaller ones clustered in their axils — 132.
110a. Flower-stalk 1-5 dm. high, 1-flowered (spring) Coltsfoot, Tussilago farfara.
110b. Flower-stalk 1-3 m. high, several-flowered (summer) Prairie Dock, Silphium terebinthinaceum.
111a. Ray-flowers pistillate (the 2-lobed style protrudes from their base) — 112.
111b. Ray-flowers with neither stamens nor pistil — 118.
112a. Principal leaves lobed (summer) (Leafcup) — 113.  
112b. Principal leaves toothed or entire, not lobed — 115.
113a. Rays 10 or more (1-2 m. high) Leafcup, Polymnia uvedalia.
113b. Rays 5 (5-15 dm. high) — 114.
114a. Rays shorter than the involucre or none Leafcup, Polymnia canadensis.
114b. Rays about 1 cm. long Leafcup, Polymnia canadensis var. radiata.
115a. Stem 6 dm. high or less; pappus of slender hairs (spring) Arnica, Arnica cordifolia.
115b. Stem usually 8-20 dm. high; pappus of short scales or none (summer) — 116.
116a. Leaves united at base into a cup surrounding the stem Cup Plant, Silphium perfoliatum.
116b. Leaves closely sessile with a rounded base Rosin Weed, Silphium integrifolium.
116c. Leaves tapering to a short petiole; principal leaves whorled Rosin Weed, Silphium trifoliatum.
116d. Leaves abruptly rounded at the sessile base, all opposite (Ox-eye) — 117.
117a. Leaves smooth Ox-eye, Heliopsis helianthoides.
117b. Leaves rough Ox-eye, Heliopsis scabra.
118a. Principal stem-leaves lobed or divided — 119.
118b. Principal stem-leaves entire or serrate — 127.
119a. Submerged aquatic; leaf-segments filiform Water Marigold, Bidens beckii.
119b. Terrestrial plants; leaves merely 3-lobed (3-8 dm. high; late spring and summer) (Tickseed) — 120.
119c. Terrestrial plants; leaves compound or dissected (summer and autumn) — 121.
120a. Leaf-lobes linear-oblong, all about equal Tickseed, Coreopsis palmata.
120b. Lateral leaf-lobes very much smaller than the terminal Tickseed, Coreopsis lanceolata.
121a. Leaf-segments entire (Tickseed) — 122.
121b. Leaf-segments serrate (5-15 dm. high) (Tickseed Sunflower) — 124.
122a. Leaf-segments numerous, linear or nearly so (4-10 dm. high) — 123.
122b. Leaf-segments 3-5, lanceolate (1-3 m. high) Tickseed, Coreopsis tripteris.
123a. Rays yellow throughout Tickseed, Coreopsis verticillata.
123b. Rays brown, at least at the base Tickseed, Coreopsis tinctoria.
124a. Achenes wedge-shape, the inner ones less than 2 mm. wide — 125.
124b. Achenes obovate, the inner ones more than 2 mm. wide Tickseed Sunflower, Bidens aristosa.
125a. Leaf-lobes lanceolate Tickseed Sunflower, Bidens trichosperma.
125b. Leaf-lobes linear Tickseed Sunflower, Bidens trichosperma var. tenuiloba.
126a. Outer leaf-like bracts 10-16; achenes brown Beggar Ticks, Bidens vulgata.
126b. Outer leaf-like bracts 5-8; achenes black Beggar Ticks, Bidens frondosa.
126c. Outer leaf-like bracts about 4 Beggar Ticks, Bidens discoidea.
127a. Bracts of the involucre all essentially alike in form and texture (flowers in summer and autumn) (Sunflower) — 179.
127b. Bracts of the involucre in two distinct sets, differing in form or consistency or both — 128.
128a. Leaves entire (3-8 dm. high; late spring and summer) — 120b.
128b. Leaves serrate (late summer and autumn) (Bur Marigold) — 129.
129a. Rays large and conspicuous, 2-3 cm. long (3-10 dm. high) Bur Marigold, Bidens laevis.
129b. Rays 1 cm. long or less — 130.
130a. Outer bracts leaf-like, serrate, 3-8 cm. long (4-15 dm. high) Bur Marigold, Bidens comosa.
130b. Outer bracts 1-2.5 cm. long (2-15 dm. high) — 131.
131a. Heads nodding after flowering Bur Marigold, Bidens cernua.
131b. Heads permanently erect Bur Marigold, Bidens connata.
132a. Heads small, seldom more than 1 cm. wide, including the rays, blooming in late summer and autumn; flowers numerous, crowded in spikes, racemes, corymbs, or panicles (Goldenrod) — 133.
132b. Heads medium size or large, more than 1 cm. and usually exceeding 2 cm. in width, including the rays — 165.
133a. Heads chiefly in clusters or short racemes in the axils of ordinary foliage leaves, or occasionally the upper compacted into a leafy cluster terminating the stem — 134.
133b. Heads crowded at or near the ends of the branches at about the same distance from the base of the panicle, forming a rounded or flat-topped inflorescence — 140.
133c. Heads more or less uniformly distributed along the length of the branches, forming a cylindrical or pyramidal inflorescence, never flat-topped — 146.  
134a. Stem and both sides of the leaves more or less pubescent or rough (4-10 dm. high) — 135.
134b. Stem and both sides of the leaves essentially smooth or with very short hairs (3-10 dm. high) — 136.
135a. Rays white Goldenrod, Solidago bicolor.
135b. Rays yellow Goldenrod, Solidago hispida.
136a. Basal leaves abruptly narrowed to winged petioles — 137.
136b. Basal leaves not abruptly narrowed to winged petioles — 138.
137a. Involucre 2-5 mm. long Goldenrod, Solidago latifolia.
137b. Involucre 8-12 mm. long Goldenrod, Solidago macrophylla.
138a. Lower leaves broadly oval, obtuse, thickish, crenate; achenes glabrous Goldenrod, Solidago erecta.
138b. Lower leaves lanceolate, acuminate, thin, sharply serrate; achenes hairy — 139.
139a. Stem usually simple; heads few in very small clusters Goldenrod, Solidago caesia var. axillaris.
139b. Stem usually diffusely branched; heads numerous Goldenrod, Solidago caesia.
140a. Lower leaves ovate, oblong, or oval, pinnately veined (5-15 dm. high) — 141.
140b. Lower leaves linear-lanceolate. 3-5-veined (3-12 dm. high) — 142.
141a. Stem and leaves rough-hairy Goldenrod, Solidago rigida.
141b. Stem and leaves smooth Goldenrod, Solidago ohioensis.
142a. Heads very few in a small cluster; leaves few and scattered Goldenrod, Solidago houghtonii.
142b. Heads very many, in a large cluster; stem very leafy — 143.
143a. Leaves hairy Goldenrod, Solidago graminifolia var. nuttallii.
143b. Leaves smooth — 144.
144a. Leaves folded, 8-20 mm. wide Goldenrod, Solidago riddellii.
144b. Leaves flat, 1-8 mm. wide — 145.
145a. Leaves 4-8 mm. wide, distinctly 3-5-ribbed Goldenrod, Solidago graminifolia.
145b. Leaves 1-4 mm. wide, usually with 1 mid-vein Goldenrod, Solidago tenuifolia.
146a. Only 2-5 stem-leaves below the inflorescence (1-3 dm. high) Goldenrod, Solidago cutleri.
146b. Stem-leaves numerous — 147.
147a. Basal leaves much larger than the greatly reduced or bract-like upper ones — 148.  
147b. Leaves essentially uniform in size from base to summit of stem — 157.
148a. Racemes or branches of the panicle either short and arranged along a more or less elongated central axis, or elongated and ascending, scarcely recurved, forming a narrow, more or less elongated panicle — 149.
148b. Racemes or branches of the panicle usually elongated, spreading outwards, usually recurved, forming a widened panicle — 153.
149a. Leaves mostly entire, the upper ones with smaller leaves fascicled in the axils (5-20 dm. high) Goldenrod, Solidago speciosa.
149b. Leaves mostly serrate, at least the basal ones — 150.
150a. Heads on pedicels 5-15 mm. long; achenes pubescent; stems usually clustered (1-5 dm. high, or prostrate) — 151.
150b. Heads on pedicels not over 5 mm. long; achenes smooth or nearly so; stems usually single (6-12 dm. high) — 152.
151a. Basal leaves 7-12 cm. long Goldenrod, Solidago racemosa.
151b. Basal leaves 15-30 cm. long Goldenrod, Solidago racemosa var. gillmani.
152a. Leaves pinnately veined Goldenrod, Solidago uliginosa.
152b. Leaves 3-5-ribbed Goldenrod, Solidago neglecta.
153a. Both sides of the leaf pubescent or rough — 154.
153b. Leaf not pubescent or rough on both sides — 155.
154a. Stem closely pubescent (2-8 dm. high) Goldenrod, Solidago nemoralis.
154b. Stem glabrous (5-12 dm. high) Goldenrod, Solidago juncea var. scabrella.
155a. Leaves rough above, smooth below (6-15 dm. high) Goldenrod, Solidago patula.
155b. Leaves smooth on both sides (5-12 dm. high) — 156.
156a. Branches of the panicle spreading or recurved Goldenrod, Solidago juncea.
156b. Branches of the panicle upright Goldenrod, Solidago juncea var. ramosa.
157a. Stem more or less pubescent or hairy throughout (5-20 dm. high) — 158.
157b. Stem smooth, at least below the inflorescence — 161.
158a. Involucre 2-2.7 mm. long Goldenrod, Solidago canadensis.
158b. Involucre 3-5 mm. long — 159.
159a. Leaves pinnately veined, scabrous above Goldenrod, Solidago rugosa.
159b. Leaves 3-5-ribbed, pubescent but not scabrous above — 160.
160a. Stem and lower side of leaves covered with short hairs; common species Goldenrod, Solidago altissima.
160b. Stem and lower side of leaves with distinct, loose, soft hairs (shore of Lake Superior) Goldenrod, Solidago altissima var. procera.
161a. Involucre 2-2.7 mm. long (5-20 dm. high) — 158a.
161b. Involucre 3-6 mm. long — 162.
162a. Racemes or branches of the panicle either short and arranged along a more or less elongated axis, or elongated and ascending, scarcely recurved, forming a narrow more or less elongated panicle (5-10 dm. high) Goldenrod, Solidago speciosa var. angustata.
162b. Racemes or branches of the panicle usually elongated, spreading outward, usually recurved, forming a widened panicle; leaves distinctly serrate — 163.
163a. Leaves pinnately veined (5-12 dm. high) Goldenrod, Solidago ulmifolia.
163b. Leaves 3-5-ribbed (5-20 dm. high) — 164.
164a. Leaves glabrous on both sides Goldenrod, Solidago serotina.
164b. Leaves slightly pubescent beneath Goldenrod, Solidago serotina var. gigantea.
165a. Ray-flowers pistillate (the 2-lobed style protrudes from their base) — 166.
165b. Ray-flowers with neither stamens nor pistil — 174.
166a. Principal leaves more than 2 dm. long (1-3 m. high; summer) — 167.
166b. Principal leaves less than 1.5 dm. long — 168.
167a. Leaves deeply lobed Compass Plant, Silphium laciniatum.
167b. Leaves toothed or serrate Elecampane, Inula helenium.
168a. Leaves narrowly linear (3-6 dm. high; late summer) Sneezeweed, Helenium tenuifolium.
168b. Leaves of a broader shape — 169.
169a. Heads 1-2 cm. wide; flowers in spring and early summer (2-8 dm. high) (Ragwort) — 170.
169b. Heads 2-5 cm. wide; flowers in late summer and autumn — 173.
170a. Basal leaves cordate at base Ragwort, Senecio aureus.
170b. Basal leaves narrowed to the base — 171.
171a. Basal leaves obovate Ragwort, Senecio obovatus.
171b. Basal leaves oblong Ragwort, Senecio balsamitae.
172a. Introduced annual in waste places (1-4 dm. high; spring and summer) Groundsel, Senecio vulgaris.
172b. Native biennial in moist ground (3-8 dm. high; summer) Squaw Weed, Senecio discoideus.
173a. Leaves 2-5 cm. long, sharply spinulose-serrate; involucre viscid (3-6 dm. high; summer) Gum Plant, Grindelia squarrosa.
173b. Leaves 5-12 cm. long, merely serrate; involucre gray-pubescent (5-15 dm. high; late summer) Sneeze Weed, Helenium autumnale.
174a. Disk hemispherical or oblong-cylindrical (Summer) — 175.
174b. Disk flat or somewhat convex (Sunflower) (summer and autumn) — 179.
175a. Disk yellow or greenish-yellow (1-3 dm. high) — 176.
175b. Disk gray-brown or purple (5-15 dm. high) — 177.
176a. Principal stem-leaves pinnately divided Golden Glow, Rudbeckia laciniata.
176b. Principal stem-leaves merely serrate Yellow Ironweed, Actinomeris alternifolia.
177a. Rays drooping; leaves pinnately divided Gray-headed Coneflower, Lepachys pinnata.
177b. Rays spreading when in bloom — 178.
178a. Lower leaves deeply 3-lobed Coneflower, Rudbeckia triloba.
178b. Stem-leaves sharply serrate Coneflower, Rudbeckia speciosa var. sullivantii.
178c. Stem-leaves entire or sparingly serrate Black-eyed Susan, Rudbeckia hirta.
179a. Disk-flowers brown or purple — 180.
179b. Disk-flowers yellow — 182.
180a. Stem-leaves ovate or ovate-lanceolate; petioles prominent, not winged — 181.
180b. Stem-leaves ovate or ovate-lanceolate, contracted at the base into a winged petiole (6-15 dm. high) Sunflower, Helianthus atrorubens.
180c. Stem-leaves oblong-lanceolate, very thick and rigid, gradually narrowed to a sessile or short-petioled base (5-20 dm. high) Sunflower, Helianthus scaberrimus.
181a. Disk less than 2 cm. wide (3-10 dm. high) Sunflower, Helianthus petiolaris.
181b. Disk more than 2.5 cm. wide (1-3 m. high) Sunflower, Helianthus annuus.
182a. Leaves all or chiefly at the base (5-10 dm. high) Sunflower, Helianthus occidentalis.
182b. Leaves chiefly scattered on the stem — 183.
183a. Leaves mainly or all alternate, and not definitely 3-ribbed (1-4 m. high) — 184.
183b. Leaves mainly or all opposite, lanceolate to ovate, and 3-ribbed — 186.
184a. Stem glabrous Sunflower, Helianthus grosse-serratus.
184b. Stem hairy or rough — 185.
185a. Leaves hairy beneath, rough above, lanceolate Sunflower, Helianthus giganteus.
185b. Leaves rough on both sides, elongated Sunflower, Helianthus maximiliani.
186a. Leaves sessile (5-15 dm. high) — 187.
186b. Leaves petioled, or narrowed at the base into a petiole (5-30 dm. high) — 189.
187a. Leaves wedge-shape at the base Sunflower, Helianthus doronicoides.
187b. Leaves rounded at the base — 188.
188a. Stem glabrous or nearly so Sunflower, Helianthus divaricatus.
188b. Stem densely and softly hirsute Sunflower, Helianthus mollis.
189a. Stems rough, pubescent, or hispid — 190.
189b. Stems glabrous or nearly so — 193.
190a. Leaves narrowly lanceolate, more than 5 times as long as wide Sunflower, Helianthus giganteus var. subtuberosus.
190b. Leaves ovate-lanceolate, not more than 4 times as long as wide — 191.
191a. Leaves rounded at base, above the petiole Sunflower, Helianthus hirsutus.
191b. Leaves narrowed to the base — 192.
192a. Bracts of the involucre spreading Jerusalem Artichoke, Helianthus tuberosus.
192b. Bracts all appressed Sunflower, Helianthus laetiflorus.
193a. Heads 3 cm. wide or less, including the rays Sunflower, Helianthus microcephalus.
193b. Heads 4 cm. wide or more, including the rays — 194.
194a. Leaves narrowed at the base into a winged petiole — 195.
194b. Petiole slender, not winged Sunflower, Helianthus decapetalus.
195a. Leaves green on both sides; bracts longer than the disk Sunflower, Helianthus tracheliifolius.
195b. Leaves paler below than above; bracts not longer than the disk — 196.
196a. Leaves minutely pubescent beneath Sunflower, Helianthus strumosus.
196b. Leaves conspicuously downy beneath Sunflower, Helianthus strumosus var. mollis.
197a. Leaves all basal, the flowers on scaly stalks (2-8 dm. high; flowers whitish, in spring) Coltsfoot, Petasites palmata.
197b. Stem-leaves present, opposite — 198.
197c. Stem-leaves present, alternate — 200.
198a. Leaves ovate, dentate, 2-6 cm. long (2-8 dm. high; summer) (Galinsoga) — 199.
198b. Leaves lobed, 10-25 cm. long — 113b.
199a. Pubescence sparse, appressed Galinsoga, Galinsoga parviflora.
199b. Pubescence abundant, spreading Galinsoga, Galinsoga parviflora var. hispida.
200a. Leaves dissected or deeply lobed or pinnatifid; pappus never capillary; rays white to pink (3-10 dm. high; summer and autumn) — 201.
200b. Leaves entire or serrate — 206.
201a. Heads 4-8 mm. wide (Yarrow) — 202.
201b. Heads 12-50 mm. wide — 203.
202a. Flower-clusters flat-topped Yarrow, Achillea millefolium.
202b. Flower-clusters very convex Yarrow, Achillea lanulosa.
203a. Principal leaves pinnatifid — 213a.
203b. Principal leaves 1-3 times pinnately parted or dissected — 204.
204a. Leaf-segments very narrowly linear; leaves 2-3-pinnate — 205.
204b. Leaf-segments linear or lanceolate; heads 2.5-5 cm. wide Camomile, Anthemis arvensis.
204c. Leaf-segments ovate to ovate-oblong; heads 1-2 cm. wide Feverfew, Chrysanthemum parthenium.
205a. Foliage strongly scented Dog Fennel, Anthemis cotula.
205b. Foliage not ill-scented Wild Camomile, Matricaria inodora.
206a. Heads 3-6 mm. broad, including the rays (summer and autum) — 207.
206b. Heads 7 mm. broad or larger, including the rays — 209.
207a. Rays purple (1-4 dm. high) Horse Weed, Erigeron divaricatus.
207b. Rays white — 208.
208a. Leaves obovate to oblong (3-10 dm. high) — 135a.  
208b. Leaves linear or narrowly lanceolate (2-25 dm. high) Horse Weed, Erigeron canadensis.
209a. Pappus none, or minute and not of hairs (summer and autumn) — 210.
209b. Pappus of hairs — 214.
210a. Disk-flowers purple or brown (4-12 dm. high; rays pink) (Purple Coneflower) — 211.
210b. Disk-flowers yellow or nearly white — 212.
211a. Leaves ovate or ovate-lanceolate, most of them serrate Purple Coneflower, Brauneria purpurea.
211b. Leaves narrowly lanceolate, gradually narrowed at the base, entire Purple Coneflower, Brauneria pallida.
212a. Rays broadly obovate; heads 1-2 cm. wide (3-6 dm. high) Sneezewort, Achillea ptarmica.
212b. Rays oblong or narrowly elliptical — 213.
213a. Leaves serrate (3-10 dm. high) Ox-eye Daisy, Chrysanthemum leucanthemum var. pinnatifidum.
213b. Leaves entire (8-25 dm. high) Boltonia, Boltonia asteroides.
214a. Involucral bracts all the same length or nearly so and narrow, or with a few short outer ones; plants blooming in spring and summer, or a few plants persisting in bloom until autumn (Fleabane) — 215.
214b. Involucral bracts unequal, the outer successively shorter (or rarely nearly equal), loosely or closely overlapping; plants 3-15 dm. high, blooming in late summer and autumn (Aster) — 221.
215a. Rays short and inconspicuous, barely longer than the pappus (1-5 dm. high; summer) Fleabane, Erigeron acris var. asteroides.
215b. Rays conspicuous, spreading, 3 mm. long or more — 216.
216a. Rare plants of the Northern Peninsula, with entire leaves and stems 1-5 dm. high, from a thick woody root (flowers white or purple, summer) — 217.
216b. Common species, with erect stems from fibrous roots; leaves toothed (except in one species) — 218.
217a. Heads 3-5 cm. wide; rays about 100 Fleabane, Erigeron glabellus.
217b. Heads 1-2 cm. wide; rays 20-30 Fleabane, Erigeron hyssopifolius.
218a. Stem unbranched, except for the peduncles; leaves chiefly basal; heads 1-9 (2-5 dm. high; flowers pale-purple, spring) Fleabane, Erigeron pulchellus.
218b. Stem branched; principal leaves on the stem; heads usually numerous (3-12 dm. high; spring and summer) — 219.
219a. Stem-leaves linear, entire Fleabane, Erigeron ramosus.
219b. Stem-leaves ovate-lanceolate, the principal ones toothed — 220.
220a. Rays 100 or more, light-purple or pink Fleabane, Erigeron philadelphicus.
220b. Rays much fewer, white Fleabane, Erigeron annuus.
221a. Basal leaves petioled and heart-shape at the base — 222.
221b. Basal leaves not petioled; stem-leaves with heart-shape clasping bases — 231.
221c. Basal and stem-leaves sessile or petioled, but never heart-shape or clasping — 240.
222a. Rays white or violet — 223.
222b. Rays blue — 225.
223a. Plant glandular, especially on the pedicels and branches of the inflorescence Aster, Aster macrophyllus.
223b. Plant not glandular — 224.
224a. Leaves rough above Aster, Aster schreberi.
224b. Leaves smooth above Aster, Aster divaricatus.
225a. Stem-leaves clasping the stem by a cordate base Aster, Aster undulatus.
225b. Stem-leaves not cordate-clasping — 226.
226a. Leaves entire — 227.
226b. Leaves serrate — 228.
227a. Leaves glabrous above Aster, Aster shortii.
227b. Leaves rough above Aster, Aster azureus.
228a. Involucre 4-6 mm. long — 229.
228b. Involucre 6-10 mm. long — 230.
229a. Leaves rough; petioles mostly winged Aster, Aster lowrieanus.
229b. Leaves smooth; petioles slender, not winged Aster, Aster cordifolius.
230a. Heads few, seldom more than 10, in a loose spreading cluster Aster, Aster lindleyanus.
230b. Heads numerous, in a rather elongate crowded cluster Aster, Aster sagittifolius.
231a. Stem hirsute or rough-pubescent — 232.
231b. Stem smooth, or essentially so — 236.
232a. Leaves conspicuously serrate Aster, Aster puniceus.
232b. Leaves entire or nearly so — 233.
233a. Leaves narrowed toward the base and barely clasping, linear or oblong-linear — 234.
233b. Leaves ovate-oblong or lanceolate, with a broad conspicuously clasping base — 235.
234a. Involucre pubescent but not glandular Aster, Aster amethystinus.
234b. Involucre glandular Aster, Aster oblongifolius.
235a. Involucre very glandular and viscid; rays very numerous, violet-purple; leaves lanceolate Aster, Aster novae-angliae.
235b. Involucre slightly glandular or not at all; rays 20-30, generally blue-purple; leaves ovate-oblong Aster, Aster patens.
236a. Leaves of a linear type — 237.
236b. Leaves broader than linear, at least 1 cm. wide — 238.
237a. Bracts narrow, approximately equal in length — 253a.
237b. Bracts of several lengths, the outer successively shorter — 256a.
238a. Leaves smooth above Aster, Aster laevis.
238b. Leaves rough above — 239.
239a. Leaves contracted below the middle and then abruptly dilated to the clasping base Aster, Aster prenanthoides.
239b. Leaves gradually narrowed toward the base Aster, Aster puniceus.
240a. Rays conspicuous — 241.
240b. Rays minute or wanting Aster, Aster angustus.
241a. Stems and leaves gray with a silky pubescence Aster, Aster sericeus.
241b. Stem and leaves green, not silky — 242.
242a. Bracts glandular-viscid; rays violet Aster, Aster oblongifolius.
242b. Bracts bristly-ciliate — 243.
242c. Bracts smooth or pubescent, not glandular or bristly-ciliate — 244.
243a. Leaves crowded, rigid; rays white Aster, Aster multiflorus.
243b. Leaves not crowded and rigid; rays blue — 234a.
244a. Bracts narrowed at the tip into thickened firm green awl-shape points — 245.
244b. Bracts acute or obtuse at the flattened tip — 247.
245a. Involucre 4-5 mm. long — 246.
245b. Involucre 7-8 mm. high Aster, Aster polyphyllus.
246a. Stem smooth Aster, Aster ericoides.
246b. Stem hairy; leaves linear Aster, Aster ericoides var. villosus.
246c. Stem densely white-woolly Aster, Aster ericoides var. platyphyllus.
247a. Leaves at most 4.5 cm. long — 248.
247b. Leaves larger, at least the principal ones — 249.
248a. Stems in clusters; leaves rigid, linear, with 1 vein; flowers blue Aster, Aster linariifolius.
248b. Stem solitary; leaves not rigid; flowers rose-pink Aster, Aster nemoralis.
249a. Heads solitary at the end of minutely leafy branchlets; leaves linear Aster, Aster dumosus.
249b. Heads in flat-topped clusters; leaves lanceolate or broader — 250.
249c. Heads in more or less one-sided racemes — 251.
249d. Heads in panicles or irregular clusters — 253.
250a. Leaves rigid, linear-lanceolate Aster, Aster ptarmicoides.
250b. Leaves not rigid, lanceolate Aster, Aster umbellatus.
251a. Leaves lanceolate, sharply serrate — 252.
251b. Leaves linear or narrowly linear-lanceolate, only the larger ones with a few teeth near the middle Aster, Aster vimineus.
252a. Stem glabrous or somewhat pubescent Aster, Aster lateriflorus.
252b. Stem woolly with long hairs Aster, Aster lateriflorus var. hirsuticaulis.
253a. Bracts narrow, approximately equal in length Aster, Aster longifolius.
253b. Bracts of several lengths, the outer successively shorter — 254.
254a. Heads 10-15 mm. wide, including the rays Aster, Aster tradescanti.
254b. Heads 15-25 mm. wide, including the rays — 255.
255a. Bracts with conspicuous dilated or subrhombic tips Aster, Aster salicifolius.
255b. Bracts without conspicuous green tips — 256.
256a. Rays purple or rose; bog plant with linear leaves Aster, Aster junceus.
256b. Rays white, or slightly tinged with blue; leaves oblong to narrowly lanceolate Aster, Aster paniculatus.