Bolboschoenus maritimus (Prairie Bulrush)

Plant Info
Also known as: Cosmopolitan Bulrush, Sea Clubrush, Saltmarsh Bulrush
Genus:Bolboschoenus
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; wet saline soil; salt marshes, shores
Fruiting season:July - September
Plant height:20 to 60 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: round Cluster type: spike

[photo of flowering spikelet clusters] Tight hemispheric cluster of 3 to 25 stalkless spikelets (flower clusters) at the top of the stem, often with an additional 1 to 4 branches arising from the stem tip. Branches are up to 3 inches long with 1 to 10 stalkless spikelets at the branch tip; less than half of all spikelets are on the branches. Spikelets are 7 to 40 mm (3/8 to 1½ inches) long, lance-oval, blunt at the tip, orange-brown to straw-colored, with 25 or more florets spirally arranged. Florets are perfect (both male and female parts) each with a 2-parted style and subtended by a single scale. At the base of the cluster are 1 to 4 leaf-like bracts that are erect to spreading and longer than the branches, the longest up to 14 inches long and 6 mm wide.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves on a vegetative shoot] Three to 6 leaves are alternately arranged along the lower half of the stem, flat to V-shaped in cross-section, up to 16 inches long, the widest blades 7 to 12 mm (to ~½ inch) wide, and may be rough along the edges and/or the midrib on the underside.

[photo of sheath] Sheaths are membranous on the front, straight to concave at the tip, the vertical veins spreading apart near the tip leaving a veinless, triangular area at the summit. The ligule (membrane where the leaf blade meets the sheath) is obscure. Stems are erect, 3-sided in cross-section and mostly smooth, though may be slightly rough on the upper stem. Plants form colonies from stout rhizomes that terminate in a tuber (corm) from which new shoots emerge.

Fruit: Fruit type: seed without plume

[photo of scale and achenes] Fruit develops in summer, the mature achenes (seeds) dropping off individually. Scales are 5 to 8 mm long, 3 to 4 mm wide, medium brown to whitish (rarely darker brown), generally elliptic, tapered or notched at the tip but fragile and often shredding, with a straight awn up to 3 mm long, the surface and awn covered in short hairs though may become hairless. Achenes are 2.3 to 4.1 mm long, 1.9 to 2.8 mm wide, lens-shaped in cross-section, broadly urn-shaped in outline, glossy and mostly medium brown. Surrounding the base are 6 weak, barbed, light brown bristles that are half as long as the achene or less, and do not usually persist with the achene after it sheds.

Notes:

Bolboschoenus maritimus, formerly Scirpus paludosus then Schoenoplectus maritimus, is a wetland species with a range primarily from the Great Plains west, where Minnesota is on the eastern edge of its range, though the range does extend across Canada and into New England. It is one of two Minnesota Bolboschoenus species, the other is Bolboschoenus fluviatilis. Both share the common traits of a leafy and sharply 3-sided stem, sheaths that lack a distinct ligule, terminal clusters usually with 1 or more branches, 1 to several stalkless spikelets at branch tips, hairy floral scales, erect to spreading leaf-like bracts longer than the spikelet branches, and colony-forming with rhizomes that terminate in a corm.

B. maritimus is the less common and robust of the two, distinguished by veins on the sheath front that diverge near the tip, all or most of the spikelets in a tight cluster at the stem tip, the remaining spikelets grouped 1 to 10 at branch tips with only 1 to 4 branches, florets with 2-parted styles, lens-shaped achenes with 6 weak bristles all much shorter than the achene and do not usually persist with the shed achene. By comparison, B. fluviatilis is common throughout the state, has veins on the sheath front that are straight all the way to the tip, usually has most spikelets grouped 1 to 8 on branch tips (some may be clumped at the cluster base), 3-parted styles with 3-sided achenes, and has stout bristles about as long as the achene that usually persist long after the achene sheds. There are 2 recognized subspecies of B. maritimus: subsp. maritimus, believed to be introduced from Eurasia, has mostly 3-parted styles, 3-sided achenes and dark brown scales and achenes; subsp. paludosus is native to the US and described above.

Compare these with other Bulrush species, which may differ by their clump-forming habit, round stems, bracts that appear to be a continuation of the stem, less leafy stems, globular clusters of numerous small spikelets, hairless floral scales, rhizomes that lack corms, or other traits not as above.

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More photos

Photos by K. Chayka taken in Lac Qui Parle County. Photos courtesy Peter M. Dziuk taken in Lac Qui Parle County and in North Dakota.

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