Tribes Aristideae (1-2), Arundineae (3-4), Danthonieae (5-6), Oryzoideae (7-9), Bambuseae (10). Use the key to grass tribes on pages 3-4 in the Grasses of Montana to learn the distinguishing features of these tribes (Bambuseae is unknown outside of cultivation in Montana). Be sure to run all of these Montana grass samples through the keys so that you can develop an association of a taxonomic group (tribe, genus, species) with its diagnostic traits or morphologies.

1. Aristida purpurea. Perennial bunchgrass, inflorescence a contracted panicle, widespread throughout Montana, occurring on many types of soils, often weedy, the hairy ligule and short first glume distinguish this grass from Stipeae in the event all florets with tripartite awns have dispersed.

2. Aristida adscensionis. Not known from Montana. Bunched annuals common to disturbed sites mostly in the southwestern USA.

3. Phragmites australis. Rhizomatous perennials often about 2 m tall, commonly inhabits margins of ponds, marshes, and river, this largest native Montana grass also bear the largest plumose showy panicle, the rachilla bears long hairs wheras the lemmas are glabrous, these long rachilla hairs render the fall inflorescence much more feathery than the summer inflorescence.

4. Arundo donax. Not known from Montana. Tall rhizomoutous perennials often much taller than the above species (often 5-10 m tall), forming extensive stands along rivers, streams, ponds, and ditches at lower latitudes than found in Montana. This tropical Asian species is widely introduced into the southern USA, where it apparently does not set fertile seed. This genus differs from that above by occurring in warm temperate to tropical regions and by having long hairs from the base of the lemma. Pampasgrass, Cortaderia, is related to Arundo and Phragmites.

5. Danthonia unispicata. A perennial bunch grass of dry open settings including open understory and middle to subalpine elevations where Festuca may also be common. This bunchgrass is often short-lived and whithers by mid to late summer at lower elevations. The long hirsute leaf sheathe are very distinctive. This species is very similar to California oatgrass, Danthonia californica, which is a taller perennial that forms bunches of few stems and often grows among tall shrubs in open sites. Both of these Danthonia species bear spikelets with the glumes somewhat open at maturity so as to expose the florets inside (unlike other Danthonia species).

6. Danthonia intermedia. Perennial bunchgrass often of montane to subalpine open understory settings, the spikelets have glumes that conceal the floret cluster. Probably the most common Danthonia in Montana.

7. Oryza sativa. Not known from Montana. An aquatic annual, or perennial in humid tropics, the conspicuous part of the spikelet is the floret, with a laterally compressed lemma and palea, the glumes are reduced to a small cupule or are essentially absent, the two glume-like structures subtending the single floret are actually sterile lemmas, a feature unique to cultivated rice.

8. Zizania aquatica. An aquatic annual, known from plantings to enhance water fowl habitat, monoecious but the staminate spikelets positioned below the pistillate.

9. Leersia oryzoides. Native rhizomatous riparian perennials, often growing within dense stands of other grasses (e.g., Phalaris arundinaceus), leaves and stems with distinctive hairs oriented backwards (retrorse) and serving has hooks to disburse this grass, of sporadic occurrence along the larger rivers in Montana.

10. Arundinaria gigantea. Not known from Montana. Tall rhizomatous perennials, leaves with a pseudopetiole, the top of the leaf sheath bears bristles, and the ligule, if not a membrane, is reduced to a thickened rim of tissue or is nearly absent.

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