10. Schoenoplectus
saximontanus (Fernald) J. Raynal (Rocky Mountain bulrush)
Pl. 82 c, d; Map 314
Scirpus saximontanus Fernald
Scirpus supinus L. var.
saximontanus (Fernald) T. Koyama
Plants annual or apparently so, the
rhizomes absent or very short and hidden by the aerial stem bases. Stems
tufted, 4–40 cm long, stiff, circular in cross-section to slightly flattened,
sometimes appearing longitudinally ridged when dry. Leaves 2–3 near the stem
bases, all but the uppermost reduced to bladeless sheaths, this with the leaf
blade 0.5–8 cm long, C-shaped to flattened in cross-section. Leaf sheaths
oblique at the tip with a V-shaped sinus on 1 side, usually split open, the
margins of the split transparent and membranous, often becoming somewhat
shredded with age. Inflorescences of 1–10 spikelets in a sessile, headlike cluster
(rarely a second, short-stalked cluster also present), the bracts 1–2, the main
bract 3–16 cm long, the other much reduced and scalelike. Individual 1-flowered
spikelets also sometimes present at the base of the stem, usually obscured by
the encircling leaf sheath. Spikelets 5–16 mm long, ovate to lanceolate or
narrowly elliptic in outline, rounded to pointed at the tip. Spikelet scales
2.5–4.0 mm long, ovate, tan to orangish brown, papery to membranous, the green
or straw-colored midrib tapered past the main body of the scale into a short,
sharp point. Perianth bristles usually absent, rarely 1–2 present in basal
flowers, these as long as or shorter than the fruits, relatively slender,
straight to contorted or bent, retrorsely barbed. Stigmas 3. Fruits 1.3–1.7 mm
long (slightly larger in fruits of basal spikelets), obovate to broadly
elliptic in outline, 3-angled in cross-section, the surface with a fine series
of irregularly undulating, horizontal ridges, dark brown to black, shiny. 2n=50.
July–September.
Uncommon, known only from Platte and St. Charles Counties in the Missouri and Mississippi River floodplains (western U.S. east locally to Ohio). Mudflats and sandy depressions of marshes.
This species was first reported for Missouri by Schuyler (1969) and Castaner (1984), and the oldest collection from the state
(without further locality data) was cited as having originated in 1848. It is
becoming more common in the eastern portion of its range and is apparently
being spread by migrating waterfowl. It shares with S. hallii the
unusual character of amphicarpy, the production of individual florets wrapped
in the leaf sheaths at the stem bases (noticeable only by the long style
protruding from the tip of the leaf sheath).