Festuca of North America


S. G. Aiken, M. J. Dallwitz, C. L. McJannet, and L. L. Consaul

Festuca idahoensis Elmer subsp. idahoensis



Bot. Gaz. 36: 53. 1903. F. amethystina var. asperrima subvar. idahoensis (Elmer) St.-Yves, Candollea 2: 260. 1925. Type: U.S.A. Idaho: Shoshone Co., Smith's Valley, July 1900, L.R. Abrams 668. Holotype: DS. Isotype: NY.

F. ovina var. ingrata Hack. ex Beal, Grasses N. Am. 2: 598. 1896. F. ingrata (Hack. ex Beal) Rydb., Bull. Torrey Bot. Club 32: 608. 1905. F. ovina subsp. ingrata (Hack. ex Beal) Piper, Contrib. U.S. Natl. Herb. 10: 28. 1906. F. occidentalis var. ingrata (Hack. ex Beal) B. Boivin, Naturaliste Canad. 94: 505, 524. 1967. Isotype: U.S.A. Oregon: 1880, Howell 23. Isotype: US.

F. ovina var. columbiana Beal, Grasses N. Am. 2: 599. 1896. Type: U.S.A. Washington: Blue Mountain, Tukanon River, June 1892, E. R. Lake 2188. Isotype: GH! US.

F. ovina var. oregona Hack. ex Beal, Grasses N. Am. 2: 599. 1896, non F. oregona Vasey, Bot. Gaz. 2: 126. 1877. F. idahoensis var. oregona (Hack. ex Beal) C.L. Hitchc., Univ. Wash. Publ. Biol. 17: 577. 1969. Type: U.S.A. Oregon: "common over the hills," 1884, Cusick 753. Isotype US!

F. ingrata var. nudata Vasey ex Rydb., Agric. Exp. Sta. Agric. Coll. Colorado Bull. (Fl. Colorado) 100: 50. 1906. Type: U.S.A. Colorado: Middle Park, 1892, Beardslee.

F. amethystina var. asperrima subvar. robusta St.-Yves, Candollea 2: 264. 1925, pro parte. Type: U.S.A. Washington: Walla Walla Co., on high ridges of the Blue Mountains, 15 July 1896, Piper 2410. Type: GH!

Habit. Plants yellowish green or bluish gray green (sometimes adjacent plants are distinctly different colours), 30–100 cm high, densely tufted, tiller bases stiffly erect, bases purplish or not purplish, horizontal rooting stems absent. Vegetative shoots arising from within existing sheaths.

Vegetative morphology. Sheaths glabrous (usually) or glabrescent or with trichomes, conspicuous at the base of the plant, persisting for more than 1 year, remaining entire, not conspicuously splitting between the veins, open more than half their length (prophylls, 1–3 cm delicate, predominantly glabrous, inconspicuous among dense sheaths). Collars glabrous. Auricles represented by distinct, erect, swellings (small). Auricular cilia absent. Ligules 0.3–0.6 mm long, ciliate. Leaf blades (5–)8–25(–35) cm long (adjacent plants may have conspicuously long or short leaves), erect, stiffish. Adaxial blade surfaces with trichomes, abaxial blade surfaces glabrous (usually) or with trichomes (scaberulous or with long trichomes). Leaf blades flat or plicate (usually plicate, but often loosely rolled), 1–3 mm wide; 0.35–0.42–0.6 mm wide, 0.55–0.62–0.7 mm deep. Veins (4–)5(–6). Adaxial to abaxial sclerenchyma strands absent. Abaxial sclerenchyma well developed, in broad bands or continuous. Ribs 3–5. Uppermost culm leaf sheaths not inflated. Flag leaf blades (1.5–)3–7(–9.5) cm long. Culm nodes becoming exposed, 1–2; internodes glabrous, or scabrous-hirsute.

Floral morphology. Inflorescence (5–)7–12(–20) cm long. Inflorescence branches at the lowest node 1–2, appressed after anthesis (sometimes loosely so), (1.5–)3–7 cm long. Rachis angular in cross section, trichomes mainly on the ridges or trichomes over the entire surface. Spikelets aggregated towards the ends of the branches; (1–)3–7 on the longest branches; (5.8–)7.5–17(–19) mm long, (2.5–)3–6 mm wide. Proliferating spikelets absent (usually; a specimen which developed inflorescenses with proliferating spikelets, is a plant of F. idahoensis collected in Southeastern Alberta and grown outside at the Agriculture Canada, Central Experimental Farm, Ottawa. CAN 520008). Florets (2–)3–7(–9). Glumes unequal, glabrous or with trichomes, vestiture at the apex only (if trichomes are present), margins ciliate. First glume (2.5–)3–5(–6) mm long, veins 1–3. Second glume shorter than the first lemma, (3–)4–8 mm long, veins 3–4. Rachilla internodes antrorsely scabrous (or sparsely antrorsely scabrous, rachilla joints usually visible, and often conspicuously zig-zag). Lemma callus not elongated. Lemma (5–)6–8(–10) mm long, nerveless in dorsal view or sometimes with only the centre vein distinct, with trichomes, trichomes on the upper portion only; apex entire. Lemma awn 1–6(–7) mm long. Palea (5–)6–8(–9) mm long, distinctly pubescent between the keels. Lodicules with marginal teeth, glabrous, 0.9–1.1 mm long. Anthers (2.5–)3.2–4(–4.5) mm long. Ovary apex glabrous. Caryopsis 4–4.5 mm long.

Cytology. 2n = 28.

Habitat and Distribution. Native; rangeland, prairie, dry habitats. Canada: Sask., Alta., B.C.; Northwestern USA: Oreg., Wash.; Southwestern USA: Calif., Nev.; Rocky Mountains USA: Colo., Idaho, Mont., Utah, Wyo.; South Central USA: N. Mex.

Classification. Subg. Festuca L.


Festuca idahoensis was considered a distinct species by Rydberg (1917), Hitchcock and Chase (1951), Hitchcock et al. (1969), and Cronquist et al. (1977). Boivin (1967) considered the taxon to be F. occidentalis var. ingrata (Hack. ex Beal) Boivin, but this was not generally accepted and reasons for not doing so were presented by Pavlick (1983a).

That F. idahoensis was initially recognized as three varieties of F. ovina, (var. ingrata, var. oregona, and var. columbiana) is a reflection on the phenotypic plasticity observed in this species. The ranges of size variation recorded for characters in the species, as currently circumscribed, are larger than for any other taxon in the data bank. For example, among collections from Colorado there are plants from high altitudes (2500–3000 m), that often have scabrous leaves, with leaf sections smaller on average and with fewer than the 5 veins usually present in cross sections of leaves of F. idahoensis plants. Fully mature spikelets may be under 6 mm long and have only two florets, which contrasts sharply with large spikelets of F. idahoensis that may reach 19 mm in length and have as many as 9 florets.

Whether distinct subspecies or varieties within F. idahoensis s.l., beyond subsp. roemeri (Pavlick) S. Aiken should be recognized, has not been determined. Since the data for F. idahoensis includes wide ranges for character sizes, it is not surprising that the INTKEY program 'Diagnose' draws attention to problems found in separating small plants of this taxon, from F. saximontana Rydb. The taxa can be readily distinguished by the length of the awns (F. idahoensis 2–7 mm; F. saximontana up to 2.5 mm) and by the length of the anthers (F. idahoensis 2.5–4 mm; F. saximontana 1.2–2.1 mm) when these characters are present. Pre-anthesis specimens of F. idahoensis, from high altitudes, provide many identification challenges.

Pavlick (1983b) stated that in British Columbia, subsp. idahoensis occurs in grasslands and in open areas in the montane and subalpine zones. In the grasslands, it occupies relatively mesic situations; in the dry zone of southern British Columbia, it occupies the more mesic mid valley slopes. In the montane and subalpine zones, it occurs on the open, south-facing slopes, in open forests, and in grass balds. It has previously been recorded as an important component of the grasslands and dry forest vegetation of southern British Columbia east of the Cascade Mountains by Spilsbury and Tisdale (1944), Tisdale (1947), McLean and Holland (1958), Brayshaw (1965, 1970) and McLean (1970).

Idaho fescue excels many of its associated forage species in ability to withstand heavy grazing and trampling, although it will succumb to continued grazing abuse. All classes of livestock relish it in the spring, as well as later in the season, where it grows on north slopes or in cooler, moister sites and where the herbage remains tender. Under such conditions it is often grazed more closely than other associated grasses. As the season advances the plants tend to become somewhat tough and harsh, and less succulent, with a proportionate decrease in palatability for sheep. This species cures well on the ground and makes a good or very good fall forage. When accessible, it is also a good forage for winter use (Dayton 1931).


• Colour forms. Adjacent plants of F. idahoensis subsp. idahoensis show contrasting blue-green and green glaucous leaves. • Habitat in British Columbia. Photograph of Festuca grassland in British Columbia. • Close up of habitat in British Columbia. Close up of grasses in the previous habitat image. F. campestris is the dominant grass, but there are some F. idahoensis plants growing beside the marker. The site approaches the northern limit of the known range of F. idahoensis. • Natural grassland habitat. Natural grassland in British Columbia. Grasses occur at the bottom of valleys and south facing slopes, while trees occur on the north facing slopes. • Leaf anatomy. Leaf cross section of F. idahoensis subsp. idahoensis. Leaf blades are usually flat or plicate, but often loosely rolled. Flat blades are 1–3 mm wide. Plicate leaf blades are 0.35–0.42–0.6 mm wide and 0.55–0.62–0.7 mm deep, with (4-)5(-6) veins. Adaxial to abaxial sclerenchyma strands are absent. Abaxial sclerenchyma are well developed, in broad bands or continuous. There are 3–5 ribs. • Specimen of type in synonymy: GH. Specimen of type in synonymy, F. amethystina var. asperrima subvar. robusta St.-Yves. Type: U.S.A. Washington: Walla Walla Co., on high ridges of the Blue Mountains, 15 July 1896, Piper 2410, Type: GH. • Herbarium specimen of interest: NY. Annotated as an isotype of F. idahonesis Elmer. Main label reads, "Ex-herbarium of Le Roy Abrams. No. 688 Festuca ovina arizonica Smith's Meadow, Shrs(?) River, Idaho July 1, 1900". The plant designated as the the type has the collection number 668. • Herbarium specimen of interest. Considered the holotype of Festuca ingrata var. nudata Rydb. by Arnold Tiehm, Sept. 1988. The annotations suggest that this has been debated. The top left hand annotation reads, "The specimen at U.S. N.H. bears A.S.H's annotation Type of F. ingrata v. nudata Rydb. Aug. 13, 1947. C.A. Taylor". The lower annotation by A.S. Hitchcock reads, "=Festuca idahoensis Elmer. Type of F. ingrata v. nudata Rudb. (F. ovina v. nudata Vasey as syn.)". • Distribution map

The interactive key provides access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, and summaries of attributes within groups of taxa.

Cite this publication as: ‘Aiken, S.G., Dallwitz, M.J., McJannet, C.L. and Consaul, L.L. 1996 onwards. Festuca of North America: descriptions, illustrations, identification, and information retrieval. Version: 19th October 2005. http://delta-intkey.com’. Aiken, Dallwitz, McJannet, and Consaul (1997) should also be cited (see References).