The Plants of Michigan / Simple Keys for the Identification of the Native Seed Plants of the State

by Henry A. Gleason

Grasses, with linear or narrow sheathing leaves, and very small flowers without perianth in the axils of chaffy bracts, appearing in late spring and summer.

Of the large number (over 150) of grasses in Michigan, only the commonest are included here, and the student is referred to the Manuals for a full treatment of them.

Their classification depends chiefly upon the structure and arrangement of the spikelets. These consist typically of a short axis, the rachilla, almost or quite concealed by several chaffy bracts. The two lower bracts are termed glumes, and have no flowers in their axils. Above the glumes are two or more other bracts, the lemmas. In the axil of each lemma, and usually concealed by it, is a smaller bract, the palea, and between the lemma and the palea is a single flower. The number of flowers in a spikelet is therefore normally equal to the number of lemmas. The spikelets are grouped in racemes, spikes, or panicles of various size.

1a. Spikelets one-flowered [— 2.]
1b. Spikelets with 2 or more flowers [— 24.]
2a. Spikelets grouped into dense solitary cylindrical spikes [— 3.]
2b. Spikelets arranged in panicles or in panicled spikes [— 8.]
3a. Spikelets without awns or bristles, or with short awns not more than 3 mm. long [— 4.]
3b. Spikelets with awns 2-5 cm. long, terminating the bracts	Squirrel-tail, Hordeum jubatum.
3c. Bracts of the spikelet without terminal awns, but the spikelets with one or more long bristles arising from their base [— 6.]
4a. Spike-like panicle thickened in the middle, more than 1 cm. thick	Beach Grass, Ammophila arenaria.
4b. Spike little or not at all thickened in the middle, less than 1 cm. thick [— 5.]
5a. Lower bracts awned; stem erect, unbranched	Timothy, Phleum pratense.
5b. Lower scales unawned; stem branched at the base	Floating Foxtail, Alopecurus geniculatus.
6a. Bristles 5 or more at the base of each spikelet	Yellow Foxtail, Setaria glauca.
6b. Bristles 1-3 at the base of each spikelet [— 7.]
7a. Spikelets about 2 mm. long; bristles not much longer, green	Green Foxtail, Setaria viridis.
7b. Spikelets about 3 mm. long; bristles much longer, usually purple	Millet, Setaria italica.
8a. Spikelets numerous, in long slender symmetrical spikes [— 9.]
8b. Spikelets in panicles, racemes, or loose spikes [— 13.]
9a. Spikelets without awns; plants 8 dm. high or less (Crab Grass) [— 10.]
9b. Spikelets with awns; plants 12 dm. high or more [— 12.]
10a. Leaf-sheaths all glabrous.	Crab Grass, Digitaria humifusa.
10b. Lower leaf-sheaths hairy [— 11.]
11a. Axis of the spike flat, with wing-like margins	Crab Grass, Digitaria sanguinalis.
11b. Axis of the spike slender, without winged margins	Crab Grass, Digitaria filiformis.
12a. Spikes numerous, appressed to the axis of the panicle; tall marsh grass	Slough Grass, Spartina michauxiana.
12b. Spikes 2-6, widely divergent; plant of dry ground	Blue-joint, Andropogon furcatus.
13a. Spikelets subtended by an ovoid thorny involucre 3-8 mm. wide	Sand Bur, Cenchrus carolinianus.
13b. Spikelets without a thorny involucre [— 14.]
14a. Lower branches of the panicle spreading, bearing staminate flowers, the upper branches erect, with pistillate flowers; aquatic or marsh grass 2-4 m. high	Wild Rice, Zizania aquatica.
14b. Panicle uniform throughout [— 15.]
15a. Spikelets with awns 2 mm. or more long [— 16.]
15b. Spikelets not awned, or with short inconspicuous awns [— 18.]
16a. Spikelets in solitary raceme-like spikes; awn about 1 cm. long or more	Beard Grass, Andropogon scoparius.
16b. Spikelets in branching clusters; awn less than 1 cm. long [— 17.]
17a. Leaf-blade 4 mm. wide or narrower; panicle slender	Drop-seed, Muhlenbergia schreberi.
17b. Leaf-blade 6 mm. wide or more; panicle stout and coarse	Barnyard Grass, Echinochloa crus-galli.
18a. Spikelet plump and compact, its bracts closely folded about each other [— 19.]
18b. Spikelet very flat, its two bracts closely folded together	Cut-grass, Leersia oryzoides.
18c. Spikelet loose and open, somewhat flattened, its 3 bracts ascending or spreading and not closely folded about each other [— 20.]
19a. Panicle about half as long as the entire plant; leaves copiously hairy	Witch Grass, Panicum capillare.
19b. Panicle of smaller size	Panic-grasses, various species of Panicum.
20a. Panicle strongly contracted or spike-like; plants of sand-dunes — 4a.
20b. Panicle spreading or slightly contracted; axis of the spikelet beset with bristles; leaves 2 dm. long or more; marsh grass	Reed Grass, Calamagrostis canadensis.
20c. Panicle spreading or somewhat contracted, but not spike-like; axis of the spikelet without bristles [— 21.]
21a. Panicle-branches erect or ascending [— 22.]
21b. Panicle-branches strongly spreading [— 23.]
22a. The two outer scales of the spikelet one-fourth as long as the third scale, or sometimes one of them absent — 17a.
22b. The glumes at least half as long as the lemma	Wood-grass, Muhlenbergia mexicana.
23a. The chief lateral branches of the panicle dividing and bearing flowers below their middle	Red-top, Agrostis alba.
23b. The chief branches of the panicle dividing only beyond the middle	Hair Grass, Agrostis hyemalis.
24a. Spikelets arranged in two rows to form a definite spike [— 25.]
24b. Spikelets in panicles, never in definite rows [— 29.]
25a. Spikelets in a single row on one side of the axis, forming a one-sided spike	Yard Grass, Eleusine indica.
25b. Spikelets alternating on opposite sides of the axis, forming a two-rowed spike [— 26.]
26a. Spikelets in pairs at each joint, forming a dense spike (Wild Rye) [— 27.]
26b. Spikelets single at each joint, forming a loose, open or interrupted spike [— 28.]
27a. Glumes lanceolate	Wild Rye, Elymus canadensis.
27b. Glumes narrowly subulate	Wild Rye, Elymus virginicus.
28a. Spikelets with their edges toward the axis of the spike	Rye Grass, Lolium perenne.
28b. Spikelets with their sides toward the axis of the spike	Quack Grass, Agropyron repens.
29a. Glumes longer than the lemmas	Oats, Avena sativa.
29b. Glumes shorter than the lemmas [— 30.]
30a. Axis of the spikelet beset with conspicuous long hairs about equaling the lemmas; tall marsh grass 1-4 m. high	Reed, Phragmites communis.
30b. Spikelets without conspicuous long hairs [— 31.]
31a. Spikelets sessile or nearly so, forming crowded or spike-like panicles [— 32.]
31b. Spikelets distinctly panicled [— 33.]
32a. Spikelets in dense one-sided clusters at the ends of the panicle branches	Orchard Grass, Dactylis glomerata.
32b. Spikelets in an erect spike-like cluster	Prairie June-grass, Koeleria cristata.
33a. Lemmas, exclusive of the awn when present, 8 mm. long or more [— 34.]
33b. Lemmas, exclusive of the awn when present, 6 mm. long or less [— 35.]
34a. Awns on the lemmas 12 mm. long or more	Brome-grass, Bromus tectorum.
34b. Awns on the lemmas 8 mm. long or less, or none	Cheat, Bromus secalinus.
35a. Lemmas with 7 sharp conspicuous veins from base to apex	Manna Grass, Glyceria nervata.
35b. Lemmas with 3-5 inconspicuous veins [— 36.]
36a. Spikelets with 5 flowers or more [— 37.]
36b. Spikelets with 2-4 (rarely 5) flowers [— 40.]
37a. Stems tufted and decumbent at base (Love Grass) [— 38.]
37b. Stems erect (Fescue Grass) [— 39.]
38a. Spikelets 1.5 mm. wide	Love Grass, Eragrostis pilosa.
38b. Spikelets 3 mm. wide	Love Grass, Eragrostis megastachya.
39a. Lemmas with conspicuous awns	Fescue Grass, Festuca octoflora.
39b. Lemmas without awns	Fescue Grass, Festuca elatior.
40a. Tufted annual grass	Spear Grass, Poa annua.
40b. Perennials, with erect flowering stems [— 41.]
41a. Stems round	Blue Grass, Poa pratensis.
41b. Stems strongly flattened	Canadian Blue Grass, Poa compressa.

CYPERACEAE, the Sedge Family

Grass-like or rush-like plants, with linear leaves or leafless, and inconspicuous flowers in small chaffy spikes.

Over 200 species occur in Michigan, of which only the commonest are included here. For the remaining species the Manuals should be consulted.

1a. Spikes all alike [— 2.]
1b. The uppermost spike or spikes wholly staminate, the lower one or more pistillate; ovary and achene surrounded by a sac, the perigynium. Mature fruit is necessary for satisfactory identification (Sedge) [— 12.]
2a. Stems leafless, bearing one or more spikes at or near the top [— 3.]
2b. Stems leafy [— 6.]
3a. Spike one, terminal and erect (Spike Rush) [— 4.]
3b. Spikes usually more than one, lateral and spreading [— 5.]
4a. Annual, with fibrous roots	Spike Rush, Eleocharis obtusa.
4b. Perennial, with a running rootstock	Spike Rush, Eleocharis palustris.
5a. Stem round	Bulrush, Scirpus validus.
5b. Stem 3-cornered	Three-square, Scirpus americanus.
6a. Spikes axillary along the side of the stem	Dulichium, Dulichium, arundinaceum.
6b. Spikes terminal [— 7.]
7a. Spikes subtended by long conspicuous leaves which greatly exceed the flower clusters [— 8.]
7b. Spikes not conspicuously exceeded by the bract-like leaves [— 10.]
8a. Spikes in a dense head-like cluster, white-woolly at maturity	Cotton Grass, Eriophorum virginicum.
8b. Spikes not in dense heads, nor white-woolly at maturity [— 9.]
9a. Perennial by a creeping rootstock	Nut Grass, Cyperus esculentus.
9b. Perennial by hard basal corms	Cyperus, Cyperus strigosus.
10a. Bracts of the spike chestnut-brown	Twig Rush, Cladium mariscoides.
10b. Bracts of the spike green or straw-color (Sedge) [— 11.]
11a. Spikes 3-8, separate	Sedge, Carex straminea.
11b. Spikes very numerous and densely crowded	Sedge, Carex vulpinoidea.
12a. Achenes flattened	Sedge, Carex crinita.
12b. Achenes 3-angled [— 13.]
13a. Perigynium tipped with a sharp straight 2-toothed beak [— 14.]
13b. Perigynium with a short soft beak [— 17.]
14a. Perigynium thin and papery, loosely enclosing the achene [— 15.]
14b. Perigynium firm, closely enclosing the achene [— 16.]
15a. Perigynium less than 1 cm. long	Sedge, Carex hystericina.
15b. Perigynium more than 1 cm. long	Sedge, Carex lupulina.
16a. Perigynium smooth	Sedge, Carex riparia.
16b. Perigynium hairy	Sedge, Carex filiformis.
17a. Beak of the perigynium bent abruptly to one side	Sedge, Carex laxiflora.
17b. Beak of the perigynium straight	Sedge, Carex pennsylvanica.

ARACEAE, the Arum Family

Individual flowers small, but crowded on a fleshy spadix to form a conspicuous spike, usually surrounded by a green or colored spathe.