Schoenoplectus heterochaetus (Slender Bulrush)

Plant Info
Also known as: Pale Great Club-rush
Genus:Schoenoplectus
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; wet often calcareous soil; marshes, lakes, wet ditches, sloughs
Fruiting season:July - September
Plant height:5 to 8 feet
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

Spikes: Flower shape: indistinct Cluster type: panicle

[photo of spike clusters] Open, branching cluster at the top of the stem with 5 to 30 spikelets (flower clusters) usually all single on slender stalks, occasionally paired. Spikelets are 5 to 15 mm long (to ½+ inch), lance-elliptic, pointed at the tip, light brown, with 8 or more florets spirally arranged. Florets are perfect (both male and female parts) each with a 3-parted style and subtended by a single scale. At the base of the cluster is an erect bract 3/8 to 6 inches long that is C-shaped in cross-section and appears to be a continuation of the stem.

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

3 or 4 leaves are near the base of the stem; only the upper 1 or 2 may have a blade longer than the sheath. Sheaths are sometimes reddish at the base, often loose or detached from the stem, deeply V-shaped at the tip, the membranous front splitting and becoming finely fibrous with age. Stems are erect, round in cross-section, dark green, firm and not much spongy when gently squeezed. Plants form colonies from firm rhizomes.

Fruit: Fruit type: seed without plume

[photo of scale and achenes] Fruit develops in summer, the mature achenes (seeds) dropping off individually leaving the persistent scales behind. Scales are 3 to 4 mm long, about 1.5 mm wide, light orange-brown to nearly colorless with a green midrib, sometimes with a few tiny spines near the tip that are red at the base giving a spotted appearance (magnification required) or streaked with reddish lines, lance-oblong, notched at the tip with a short, straight to somewhat contorted awn. Scale edges are a bit ragged with contorted hairs. Achenes are 2.2 to 3.2 mm long, 1.4 to 1.9 mm wide, 3-sided, flat on the back with a rounded angle on the front, urn-shaped in outline, gray-brown and smooth. Surrounding the base are 4(5) barbed, light brown bristles, the 2 on the sides about the same length and about as long as the achene, those on the front and back usually much shorter.

Notes:

Schoenoplectus heterochaetus, formerly Scirpus heterochaetus, is typically found in standing water up to 5 feet deep along lake and pond margins, and may form dense stands. It closely resembles two other Minnesota Schoenoplectus species: Schoenoplectus acutus and Schoenoplectus tabernaemontani. All share the common traits of a round stem, not much for leaves, and a terminal cluster with an erect bract that appears to be a continuation of the stem. S. heterochaetus is distinguished by a firm stem that is not easily compressed when gently squeezed, the slender stalked spikelet clusters with up to 30 spikelets, spikelets almost always single but occasionally paired, florets with 3-parted styles, 3-sided achenes with 4 bristles, the 2 on the sides about as long as the achene and those on the front and back usually much shorter.

By comparison, both S. acutus and S. tabernaemontani have florets with 2-parted styles, achenes merely rounded on the front or weakly 3-sided at best, and 6 bristles all about the same length and about as long as the achene. In addition, S. acutus has stiffly stalked spikelets that are grouped in 2 to 8 with some singles, and scales more distinctly red-spotted (magnification recommended). S. tabernaemontani spikelets are mostly solitary with some in groups of 2 to 4, and the stem is quite spongy and easily compressed when gently squeezed. S. heterochaetus hybridizes with both and intermediates may be found when both parents are present. Good luck with those!

Compare these with other Bulrush species, which may differ by their 3-sided stems, leaf-like bracts, leafier stems, globular clusters of numerous small spikelets, scales that lack a notch at the tip or an awn, or other traits not as above.

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More photos

Photos by K. Chayka taken in Cass and Lake counties. Photos courtesy Peter M. Dziuk taken in Lake County.

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