Common Name: Hairgrasses
Description: Delicate annuals, with few to many slender culms in small tufts.
Leaves with ligule membranous, to 5 mm long; blade often convolute, soft, narrow, hairless.
Inflorescence an open or contracted panicle with very slender branches.
Spikelets pedicellate, small, rachilla disarticulating above the glumes and between the lemmas, laterally compressed with 2 bisexual florets. Glumes subequal, keeled, 1–3-nerved. Lemmas subequal to or shorter than the glumes, rounded on the back, firm, acute, obscurely 2–5-nerved, 2-fid with 2 slender teeth; a slender, geniculate, dorsal awn attached below the middle; sometimes 1 or both florets unawned; callus minutely pubescent. Palea slightly shorter than the lemma, narrow, 2-toothed.
Distribution and occurrence: World: c. 10 species, Europe, Asia & Africa. Australia: 5 species (naturalized), all States.
Aira species occur in dry, open habitats, often in disturbed areas, and are of little value as stock feed. Key from Wheeler et al. (1990).
Text by S. W. L. Jacobs & S. M. Hastings
Taxon concept:
| | Key to the species | |
| 1 | Panicle narrow and dense; branches short, erect; pedicels usually shorter than the spikelets | Aira praecox |
| Panicle open, spreading with divaricate branches; pedicels 1–8 times as long as the spikelets | 2 |
| 2 | Pedicels 1–2 times as long as the spikelets; glumes acute or obtuse | 3 |
| Pedicels 2–8 times as long as the spikelets; glumes acute
Back to 1 | 4 |
| 3 | Spikelets 2.5–3.5 mm long; lemma 75% the length of the acute glumes; both florets awned | Aira caryophyllea |
| Spikelets 2–2.5 mm long; lemma 50–65% as long as the obtuse glumes; lower floret often unawned
Back to 2 | Aira cupaniana |
| 4 | Spikelets 1.2–2.5 mm long; pedicels tapering gradually to the wider apex | Aira elegantissima |
| Spikelets 3.5 mm long; pedicels club-shaped, abruptly tapered to the apex
Back to 2 | Aira provincialis |
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