2. Schoenoplectus
americanus (Pers.) Volkart ex Schinz & R. Keller (saltmarsh bulrush,
Olney three-square)
Pl. 81 a, b; Map 306
Scirpus americanus Pers.
Scirpus olneyi A. Gray
Plants perennial with stout, long-creeping
rhizomes. Stems widely spaced on the rhizomes, 50–150 cm long, stiff, strongly
triangular in cross-section, the sides usually noticeably concave when fresh
(difficult to see when pressed). Leaves 2–4 near the stem bases, the lowermost
1–3 reduced to bladeless sheaths, the other 1–3 with leaf blades 3–20 cm long,
these thick, V-shaped to flattened-triangular in cross-section. Leaf sheaths
oblique at the tip with a U-shaped sinus on 1 side. Inflorescences of 2–15
spikelets in a sessile, headlike cluster, the bract 1, 1–6 cm long, other, reduced
bracts absent. Spikelets 6–15 mm long, ovate in outline, rounded to bluntly
pointed at the tip. Spikelet scales 3.5–6.0 mm long, broadly ovate, shallowly
notched at the tip, orangish brown to brown, often tinged with purple, the
green or straw-colored midrib extended past the main body of the scale as a
short awn. Perianth bristles (3–)4–6, shorter than to slightly longer than the
fruits, relatively stout and straight or slightly curved or arched around the
fruit, retrorsely barbed. Stigmas 2. Fruits 1.8–2.5 mm long, obovate in
outline, somewhat flattened, unequally biconvex in cross-section, the surface
smooth or nearly so, yellow, turning greenish brown and eventually dark brown,
shiny. 2n=78. June–September.
Uncommon and possibly extirpated, known
only from a single historical collection from Jefferson County (U.S. and adjacent Canada, south to South America). Alkaline seeps, sometimes in shallow water.
Schoenoplectus americanus was long
known as Scirpus olneyi because of confusion as to the application of
the former name. It is more common to the west of Missouri and often occurs in
strongly alkaline soils. Because winter application of road salt has turned
soils along many highways more alkaline, it is possible that this species may
become more common in the state in the future. Where S. americanus
occurs with S. pungens, sterile hybrids are sometimes formed. These are
known as S. ×contortus (Eames) T. Koyama and have not yet been
reported from Missouri. The hybrids bear a morphological resemblance to S.
deltarum (see further discussion under the treatment of that species).