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Key to Poaceae

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1 Plant a shrub or tree (the culms perennial, woody, to 25 m tall), with complex branching systems from the upper nodes; leaves strongly dimorphic, those of the main culm sheathing, those of the branches or culm tips pseudopetiolate  Key to Poaceae, Key A: bamboo grasses (woody trees and shrub grasses) (tribe Bambuseae)

1 Plant an herb (the culms annual, not truly woody, to 5 m tall), lacking complex branching systems from the upper nodes; leaves not dimorphic, none of them pseudopetiolate.

2 Plant a robust grass, culms usually > 2 m tall and usually > 5 mm in diameter at the base  Key to Poaceae, Key B: robust herbaceous grasses

2 Plant a small to medium grass, culms < 2 m tall and usually also < 5 mm in diameter at the base.

3 Spikelets either modified into asexual, purplish bulblets, or partially or wholly concealed either by spines, hooks, and/or involucres, or partially or wholly concealed by being imbedded in a fleshy rachis or cob.

4 Fertile spikelets either absent (spikelets modified into asexual, purplish bulblets) or variously spiny or bead like  Key to Poaceae, Key C: bur, bead, or bulblet grasses of various tribes

4 Fertile spikelets embedded in a fleshy rachis (resembling a rattail) or a cob  Key to Poaceae, Key D: rattail or cob grasses

3 Spikelets apparent, not covered, concealed, embedded, or modified by spines, hooks, or involucres.

5 Spikelets 2-flowered, often dorsally compressed, falling entire at maturity (the abscission below the glumes), the upper floret usually bisexual, the lower one male or sterile.

6 Glumes often as long as or longer than the lemmas and concealing the florets; spikelets usually arranged in obvious pairs or triplets, with 1 spikelet sessile or shortly pedicellate and the other 1 (or 2) spikelets pedicellate (the pedicellate sometimes vestigial or absent)  Key to Poaceae, Key E: grasses of tribe Andropogoneae (also including grasses also keyed in Keys B, C, and D)

Show caption*© Lowell Urbatsch, spikelet           6 Glumes (the lower or both) shorter than the lemmas (or the glumes absent); spikelets not organized in pairs or triplets  Key to Poaceae, Key F: grasses of tribe Paniceae (also including grasses keyed as well in Keys B, C, D, and H)

5 Spikelets 1-, 2-, or many-flowered, usually terete or somewhat laterally compressed, either abscising at maturity above the glumes or if 2-flowered then both florets bisexual, or the upper sterile.

7 Inflorescence of one or more spikes, the spikelets sessile (or very short-pedicelled) on the spike axis, 1-more per node, characteristically in 2-more ranks (these either on opposite sides of the axis or crowded on one side), the individual spikelets borne more-or-less touching one another.

8 Spikelets borne in a single terminal spike or raceme (an extension of the culm), usually 2-ranked on opposite sides of the axis  Key to Poaceae, Key G: wheat grasses of tribe Triticeae (and a few unrelated mimics)

8 Spikelets borne on 1-many spikes (the spikes themselves arranged digitately, subdigitately, or racemosely on the culm) in 2 (or more) rows; spikelets often on one side of the spike axis  Key to Poaceae, Key H: finger grasses

7 Inflorescence paniculate, sometimes somewhat to very congested, but then not as above.

9 Spikelets with a single bisexual floret, and no staminate, sterile, or reduced florets present (occasional spikelets of Muhlenbergia can have 2-3 florets).

10 Glumes absent or reduced to tiny rudiments; palea 1-keeled; [of wetlands]  Key to Poaceae, Key I: rice grasses, of tribe Oryzeae (also including grasses keyed as well in Key B)

10 Glumes present; palea various; [habitats various].

11 Inflorescences dense and spikelike, symmetrical, cylindrical or ovoid, unbranched  Key to Poaceae, Key J: dense spike grasses

11 Inflorescences loose and open, or if relatively dense, then with discernible branches, and thus lobed or asymmetrical.

12 Lemmas awnless  Key to Poaceae, Key K: grasses with 1 floret and unawned lemmas

12 Lemmas awned  Key to Poaceae, Key L: grasses with 1 floret and awned lemmas

9 Spikelets with 2-many florets, including bisexual, staminate, reduced, or sterile flowers.

13 Glumes (one or both) nearly equaling or surpassing the most apical lemma of the spikelet, therefore partially or completely concealing the florets  Key to Poaceae, Key M: grasses with 2+ florets, these exceeded and usually concealed by the glumes

13 Glumes (both) shorter than the most apical lemma of the spikelet, therefore the florets largely visible  Key to Poaceae, Key N: grasses with 2+ florets, these readily visible by extending past the glumes