Schoenoplectiella smithii (Smith's Bulrush)

Plant Info
Also known as: Blunt-scale Bulrush
Genus:Schoenoplectiella
Family:Cyperaceae (Sedge)
Life cycle:annual
Origin:native
Habitat:part shade, sun; wet sandy, muddy or peaty soil; shores, mudflats, floating mats, bogs
Fruiting season:July - October
Plant height:3 to 20 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

Spikes: Flower shape: indistinct Cluster type: spike

[photo of spike cluster and bract] One to several stalkless spikelets at the top of the stem, subtended by an erect bract that appears to be a continuation of the stem, so the spikelet(s) seem to be growing out from the side of the stem. On larger plants, the bract is up to 6 inches long, up to 2/3 as long as the stem (below the spikeles) but may be longer than the stem on smaller plants. Spikelets are 5 to 10 mm (to 3/8 inch) long, lance-elliptic, blunt to rounded at the tip, orange-brown to straw colored, the larger spikelets with up to 30 florets spirally arranged. Florets are perfect (both male and female parts) each with 3 stamens, a 2 or 3-parted style and subtended by a single scale.

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

A single leaf near the plant base is about as long as or shorter than the stem, but is often reduced to a bladeless sheath. Leaves are C-shaped in cross-section and smooth. Sheath fronts are not fibrous. Stems are round to weakly 3-sided in cross-section, 1 to 1.5 mm in diameter, erect to arching, sometimes prostrate from the base and rising at the tip (decumbent). Stems are typically multiple from the base, forming loose to dense clumps.

Fruit: Fruit type: seed_without_plume

[photo of scale and maturing achenes, var. setosus] Fruit develops summer into fall, the mature achenes (seeds) dropping off individually. Scales are 2.5 to 3 mm long, 1.5 to 2 mm wide, orange-brown to straw-colored with the green midrib area turning brown, rounded at the tip with an abrupt, sharp point (mucronate). Achenes are 1.5 to 2 mm long, urn-shaped in outline, flat on the back and rounded on the front (plano-convex) in cross-section, rounded at the tip with a short beak, more or less evenly tapered to the base, .2 to .3 mm wide at the base, faintly textured to smooth on the surface and maturing to brown then glossy blackish. Surrounding the base are 4 to 6 barbed, light brown to whitish bristles that are 1 to 2 times as long as the achene, rarely much reduced or absent altogether.

Notes:

Schoenoplectiella smithii, formerly Scirpus smithii then Scheonoplectus smithii, is an obscure bulrush that has evaded us for a long time. After many years of pursuing this species at old collection sites without success, we stumbled upon it completely by accident on a muddy, fibrous mat while canoeing around a pond in search of pondweeds. Like many annuals, it may not come up in the same place year after year, but requires suitable environmental conditions before the seed bank gives up the ghost, and our higher-than-average water levels over the past several years is probably why it's been so elusive. While it may reach heights of about 20 inches, it can be less than half that size, even a quarter—our specimens were only 4 or 5 inches tall at full maturity. It is found on sandy, mucky or peaty banks, shores and floating mats, sometimes in shallow water, often with other sedges that may hide it from all but the most observant explorers.

Schoenoplectiella was separated from Schoenoplectus primarily based on being annuals rather than perennials. S. smithii is distinguished from the only other Schoenoplectiella species in MN (S. purshiana) by the combination of: heights of up to 20 inches (often much smaller), an erect bract that can be 2/3+ as long as the stem (up to the spikelets), achenes .2 to .3 mm wide at the base with 4 to 6 bristles that are about the same width from tip to base, the bristles either 1 to 2 times as long as the achene, or diminished to absent altogether. There are 2 varieties of S. smithii, both of which have been found in Minnesota: var. setosus is the more common, preferring stable water levels and has 4 to 6 bristles up to twice as long as the achene; var. smithii prefers fluctuating water levels and its bristles are much reduced or absent altogether.

By comparison, S. purshiana may be twice the height, the bract on larger plants is usually spreading not erect and is not more than ¼ as long as the stem, achenes are .3 to .4 mm wide at the base, bristles number 6 (occasionally none), are about as long as or slightly longer than the achene, and are distinctly wider at the base than the tip. When bristles are absent the width of the achene base may be needed for a positive ID. Smaller S. smithii plants have been confused with Cyperus subsquarrosus (a.k.a. Lipocarpha micrantha or Hemicarpha micrantha), which has round to oval spikelets only 1 to 3 mm long and has 2 bracts at the base of many spikelet clusters.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken in Kanabec County.

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