Aquatic and Wetland Vascular Plants of the Northern Great Plains

Scirpus L. -- Bulrush

Stout, mostly rhizomatous, reedlike or rushlike perennials (short, tufted annual in S. saximontanus), medium to tall in stature; culms simple, trigonous or terete, solid or pithy. Leaves sheathing the stems, the blades grasslike, broad and flat to narrow and often folded or channeled above, or blades poorly developed, the leaves reduced mainly to sheathing at the base of the culms. Involucral bracts 1-several subtending the inflorescence, when 1, the bract appearing like a continuation of the culm, otherwise foliaceous. Inflorescence terminal or appearing lateral, paniculate or umbellate, the spikelets single or in glomerules on pedicels, or the inflorescence compact, with all or most of the spikelets sessile; spikelets 1-numerous; scales spirally arranged, imbricate. Flowers perfect; perianth of 1-6 retrorsely barbed bristles, rarely absent; stamens 2 or 3; styles bifid or trifid; achenes correspondingly lenticular or trigonous, usually beaked.

References:  

Beetle, A. A.  1947. Scirpus.  North Amer. Flora 18:481-504. 

Schuyler, A. E.  1967.  A taxonomic revision of North American leafy 
     species of Scirpus.  Proc. Acad. Nat. Sci. Philadelphia 119:295-323. 
      
Schuyler, A. E.  1974.  Typification and application of the names Scirpus 
     americanus Pers., S. olneyi Gray and S. pungens Vahl. 
     Rhodora 76:51-52. 

Ward, R. L.  1973.  A cytotaxonomic study of the Scirpus lacustris L. 
     complex in the northern Great Plains.  Unpubl. Ph.D. thesis, N. Dak. 
     State Univ., Fargo.

Lead	Characteristic	Go To
1	Principal involucral bract 1, erect or nearly so, resembling a continuation of the culm; inflorescence appearing lateral.	Lead 2
1	Principal involucral bracts 2-several, foliaceous and spreading; infloresence terminal.	Lead 7
2	Plants annual, tufted; achenes cross-ridged.	S. saximontanus
2	Plants perennial, rhizomatous; achenes smooth or reticulate.	Lead 3
3	Spikelets 1-6, sessile in a cluster.	Lead 4
3	Spikelets numerous, pedicelled singly or in clusters, borne in a dense to open panicle.	Lead 5
4	Stems trigonous; scales aristate, bifid.	S. pungens
4	Stems terete or nearly so; scales acute to obtuse.	S. nevadensis
5	Styles trifid; achenes trigonous; perianth of 2-4 bristles; spikelets solitary (rarely paired) on the pedicels.	S. heterochaetus
5	Styles bifid (rarely trifid); achenes lenticular; perianth of 6 bristles; spikelets mostly in glomerules of (1)2-8(15) on the pedicels.	Lead 6
6	Spikelets mostly in glomerules of 3-8(15), grayish-brown; culms dark green and resistant to crushing when fresh, fading with drying.	S. acutus
6	Spikelets mostly single or in pairs, reddish-brown; culms light green and easily crushed when fresh.	S. tabernaemontani
7	Spikelets few to many, 10-50 mm long, 6-12 mm thick; achenes 2.5-4.5 mm long; culms sharply trigonous.	Lead 8
7	Spikelets very numerous, 3-10 mm long, 1-1.5 mm thick; achenes ca. 1 mm or less long; culms obtusely trigonous.	Lead 9
8	Styles trifid; achenes trigonous; leaf sheaths convex at the mouth, the ventral nerves abruptly divergent at the summit.	S. fluviatilis
8	Styles bifid; achenes lenticular; leaf sheaths truncate or concave at the mouth, the ventral nerves gradually divergent at the summit.	S. maritimus
9	Perianth bristles much contorted, smooth, not barbellate, equaling or exceeding the scales.	Lead 10
9	Perianth bristles straight to curved, barbellate, shorter than to equaling the scales.	Lead 11
10	Perianth bristles conspicuously surpassing the scales, giving the spikelets a woolly appearance.	S. cyperinus
10	Perianth bristles about equaling the scales, the spikelets not woolly in appearance.	S. pendulus
11	Leaf sheaths partly red-tinged; styles bifid.	S. microcarpus
11	Leaf sheaths entirely green; styles trifid.	S. pallidus

62. Cyperaceae, the Sedge Family

11. Scirpus L. -- Bulrush

1. Scirpus acutus Muhl. ex Bigel. -- Hardstem bulrush

2. Scirpus cyperinus (L.) Kunth. -- Wool grass

3. Scirpus fluviatilis (Torr.) A. Gray -- River bulrush

4. Scirpus heterochaetus Chase -- Slender bulrush

5. Scirpus maritimus L. -- Prairie bulrush

6. Scirpus microcarpus Presl -- Redstem bulrush

7. Scirpus nevadensis S. Wats. -- Nevada bulrush

8. Scirpus pallidus (Britt.) Fern. -- Pale bulrush

9. Scirpus pendulinus Muhl.

10. Scirpus pungens Vahl -- Three-square

11. Scirpus saximontanus Fern.

12. Scirpus tabernaemontani Gmel. -- Softstem bulrush

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