Festuca saximontana (Rocky Mountain Fescue)
|Also known as:||Mountain Fescue|
|Habitat:||sun; dry sandy or rocky soil; prairies, jack pine stands, roadsides, sandy banks, bluffs, rock outcrops, rock crevices|
|Plant height:||4 to 20 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Spike-like panicle at the top of the stem, 1 to 4+ inches long, the short branches usually erect but may be ascending at flowering time, with 1 or 2 branches per node, the lowest branches with 2 or more spikelets (flower clusters). Spikelets are short-stalked, green to purplish at flowering time, 3 to 10 mm (to ~3/8 inch) long, flattened, lance-elliptic in outline and have 2 to 7 florets, usually 3 or 4; the floret at the tip may be sterile.
At the base of a spikelet is a pair of bracts (glumes), both awnless, hairless, shorter than the spikelet, pointed at the tip, not keeled, the lower glume 1.5 to 3.5 mm long and 1-veined, the upper glume 3-veined, 2.5 to 4.8 mm long. Florets are surrounded by a pair of bracts (lemma and palea), the lemma 5-veined, not keeled, 3 to 5(5.6) mm long excluding a straight awn 1 to 2 mm long, the lowest lemma as long as or somewhat longer than the upper glume; the palea is about as long as the lemma, 2-veined, minutely hairy across the tip end. Stamen tips (anthers) are less than 2 mm long. Sterile florets are like the fertile but underdeveloped.
Leaves and stems:
Leaves are mostly basal, folded, 1 to 8 inches (to 20 cm) long, to 1.2 mm wide (2.4 mm when flattened), have 1 conspicuous rib and may have 1 or 2 pairs of obscure lateral ribs, are hairless or minutely hairy near the base or on the ribs. Basal sheaths are conspicuous, persistent, green soon dying and drying tan, and rarely shred into fibers. Sheaths of new shoots (tillers) are green, mostly hairless, and the edges fused for 1/3 to half of their length (closed sheath).
The 1 or 2 stem leaves are folded and usually shorter than basal leaves. The ligule (membrane where the leaf joins the sheath) is up to .5 mm long, usually higher on the ends than in the middle, and lacks a fringe of hair. Nodes are hairless. Stems are hairless, multiple from the base, more or less erect. Plants form small, dense clumps and lack rhizomes, the new shoots all emerging erect from the basal sheaths (intravaginal).
The panicle branches are typically erect when spikelets mature, drying straw-colored to light brown. Florets drop off individually as they mature, leaving the glumes persisting on the stalk. Grains (seeds) are purplish-brown.
Rocky Mountain Fescue, sometimes known as Festuca ovina var. saximontana, is a native, cool-season grass, most often found in open, dry, sandy areas such as prairies, roadsides and forest openings, but also in the cracks, crevices and ledges of bluffs and rock outcrops, particularly on the north shore of Lake Superior and near the Canadian border in our northeastern counties.
F. saximontana is generally distinguished by having dense clumps of fine leaves; sheaths of tillers (new shoots) mostly hairless and closed between 1/3 and half of their length; basal sheaths usually persistent, rarely shredding into fibers; leaves mostly basal, folded, .5 to 1.2 mm diameter (to 2.4 mm when flattened); panicle branches usually erect, sometimes spreading when flowering; spikelets with 3 to 5(7) florets, lemma awns usually 1 to 2 mm long; anthers less than 2 mm long. Foliage is green to blue-green. Leaves usually have only 1 distinct rib, the lateral 1 or 2 pair obscure at best, but it's difficult to flatten the leaves to see this. Magnification is required. There are 3 recognized varieties: var. saximontana is most common, present in Minnesota and described above; var. purpusiana and var. robertsiana are both smaller, alpine species of western North America.
There are 3 narrow-leaved Festuca species in Minnesota, the others are the non-natives F. trachyphylla and F. rubra, and they can be difficult to distinguish. F. rubra is the only one of the three that has rhizomes, reddish basal sheaths, old sheaths shredding into fibers, tiller sheaths closed for at least 75% of their length, and extravaginal shoots where new shoots break through the sheath and grow horizontally for a bit before rising up, but these traits are not so obvious without digging some out and careful picking through the clump.
F. saximontana and F. trachyphylla are more difficult to separate, but F. trachyphylla tends to be a more robust plant with larger clumps, spikelets commonly with 4 to 6 florets, larger anthers consistently at least 2 mm long, leaves with 3 to 5 distinct ribs, and tiller sheaths closed for less than 1/3 their length, frequently open nearly to the base. The folded leaves are very difficult to flatten out to see the ribs; try rolling a leaf around your finger, or folding a stem leaf down near the base to see the upper surface. Magnification is required in any case. Tiller sheaths are easier to check and are best seen while they're still green and relatively fresh, though magnification is also needed. By gently pulling a tiller apart from the top of a sheath, you can usually see where the sheath edges overlap and the point where they become fused, but this is easier to see under a dissecting microscope.
A characteristic of Festuca species is what's known as “sclerenchyma strands”, which are clusters of hardened, dead cells that run the length of the leaf just under the surface, the shape and arrangement of which are fairly distinct for each species. These cannot be seen with the naked eye and requires putting a cross-section of the leaf under a microscope. Try as I might I was not able to get a photo of this myself, but some images are out there in the web universe and Flora of North America has some illustrations online that are helpful, in case you are able to get a leaf under a scope to see for yourself. Festuca rubra has small round to elliptic strands, one at each edge and 1 opposite each vein on the lower leaf surface. F. saximontana and F. trachyphylla strands may run along most or all of the lower surface as a continuous or interrupted band.
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- Rocky Mountain Fescue plant
- Rocky Mountain Fescue plant
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- Rocky Mountain Fescue with June Grass
- scan of stem
- panicle branches may be slightly spreading at flowering time
- F. saximontana tiller sheath would be closed 1/3 to half its length
Photos by K. Chayka taken in Polk County. Photos by Peter M. Dziuk taken in Kittson County and in his garden.
Have you seen this plant in Minnesota, or have any other comments about it?