Introduction to the tribe Poeae. Use the key to grass tribes on pages 3-4 in the Grasses of Montana to learn the distinguishing features of this grass tribe, which is basically that the tribe Poeae doesn’t fit the easy characterization of the other cool season grass tribes so it is the “left over” or “garbage can” cool season grass tribe. Species of Poeae we have seen before are Bromus inermis, Bromus japonicus, Dactylis glomerata, Festuca idahoensis, Poa compressa, Poa pratensis, and Schedonorus pratensis. These represent three main subgroups, bromes, fescues, and bluegrasses, as well as one of the genera, Dactylis, characterized by contracted secund panicles. Be sure to run all of your grass samples through the keys in the Grasses of Montana so that you can develop an association of a taxonomic group (tribe, genus, species) with its diagnostic traits or morphologies.
1. Bromus carinatus (B. marginatus). Perennial bunchgrasses, inflorescence an open ascending panicle, spikelets strongly keeled, open grassy sites and open understory mostly in the mountains.
2. Bromus hordeaceus (B. mollis). Annual bunchgrasses, inflorescence a narrow panicle or raceme bearing spikelets with distinctively short and erect pedicels, lemmas distinctly hairy, inhabiting disturbed sites.
3. Bromus tectorum. Annual bunchgrasses, inflorescence an open often nodding panicle, spikelets with lemmas that narrowly taper to two narrow teeth, the width of which is not much wider than the base of the awn, inhabiting disturbed sites, mostly on the driest exposures or the most well drained sites.
4. Cynosurus echinatus. Annual bunchgrasses, inflorescence a contracted secund panicle somewhat similar to that of Dactylis, spikelets are dimorphic, one type has only numerous sterile lemmas, the other has large glumes enclosing usually two florets, inhabiting disturbed sites.
5. Vulpia octoflora. Slender annual bunchgrasses, the inflorescence is a narrow secund panicle with the secund arrangement often not readily conspicuous, the florets are rounded on back and generally well spaced along the rachilla, inhabiting moderately disturbed sites and flowering early summer.
6. Festuca campestris (F. scabrella). Perennial bunchgrasses that dominate higher elevation or northern latitudes just out of the sagebrush steppe, new basal leaf sheaths are reddish and old basal leaf sheaths have an apical zone of abscission from where the leaf blades fall, rendering a clipped appearance to the older basal leaf bunch.
7. Leucopoa kingii. Perennial bunchgrasses, similar to Festuca campestris and occurring in open dry sites in the mountains but only in very southern Montana (thus not strongly overlapping geographically with F. campestris), the ligule is not stairstepped or bilobed and the lemmas are not awn-tipped as they are in fescue grasses such as F. campestris.
8. Lolium persicum. Annual bunchgrasses, even if most of the lemmas have disarticulated on this species, the very large second glume and lemmas with a slender curving awn are conspicuous and distinctive, inhabiting disturbed areas.
9. Poa secunda. Perennial bunchgrasses usually with a basal leaf bunch but this varies considerably, the spikelets are not laterally compressed but sometimes this is evident only by the rounded individual florets, particularly the terminal one that is usually well projected on a long rachilla internode, an early summer flowering species of the sagebrush steppe as well as open grassy sites in the mountains including sometimes alpine settings.
10. Poa fendleriana (P. cusickii). Perennial bunchgrasses with a basal leaf bunch similar to Poa secunda but the inflorescence is distinctly shorter and wider than that of Poa secunda and the spikelets in contrast are strongly laterally compressed, an early summer flowering of mostly the sagebrush steppe, like Poa secunda, Poa fendleriana inhabits open dry sites at elevation up to the alpine zone, like Festuca campestris, the leaf blades often abscise from the leaf sheath along a predetermined zone at the apical end of the sheath.
11. Poa bulbosa. Perennial bunchgrasses often short-lived, stem bases commonly bulbous, spikelets with florets mostly transformed into small vegetative bulbs, competes well with other sometimes less desirable grasses on disturbed sites.
12. Puccinellia nuttalliana. Perennial bunchgrasses, inflorescence an open panicle, spikelets appressed to the rachis, lemmas blunt to rounded at tip, mostly of moist alkaline soils but occasionally scattered in open shrub-grass vegetation.