Carex sparganioides (Bur-reed Sedge)

Plant Info
Also known as: Thin-leaved Sedge
Family:Cyperaceae (Sedge)
Life cycle:perennial
Habitat:part shade, shade; moist to dry; rich woods, floodplain forest, forest edges
Fruiting season:June - July
Plant height:12 to 40 inches
Wetland Indicator Status:GP: FAC MW: FAC NCNE: FACU
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 spikes] A cluster 1 to 6 inches long at the top of the stem, made up of 6 to 15 round to oval spikes, the lowest 2 to 4 usually well separated from each other by ¾ inch or more (more than twice the length of the lowest spike). The uppermost spikes are overlapping and more crowded at the tip. The terminal spike has staminate (male) flowers at the tip and pistillate (female) flowers at the base (androgynous), with the lateral spikes usually androgynous though some may be all pistillate.. At the base of the lowest spike is a narrow, leaf-like bract up to 1 inch long and does not overtop the terminal spike. Bracts become much shorter and more bristle-like as they ascend the stem.

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

[photo of sheath and ligule] Leaves are basal and alternate, mostly near the base, erect to arching, the largest 5 to 10 mm wide, shorter than or about as long as the flowering stems, though vegetative shoots may be longer. Stem leaf sheaths loosely wrap the stem and are translucent whitish on the front, cross-wrinkled (rugose), fragile and easily torn. The ligule (membrane where the leaf joins the sheath) is about as long as wide. Leaves are hairless and V-shaped in cross-section when young.

[photo of striped sheath] The back of the sheath is longitudinally green and white striped or mottled, with green cross-veins. Bases are wrapped in a brown sheath that may become fibrous with age. Stems are erect to ascending, up to 6 mm wide at the base and much more slender above, 3-sided and rough on the upper stem, elongating up to 3 feet at maturity. Plants are clump-forming and not colony-forming.

Fruit: Fruit type: seed without plume

[close-up of developing fruit] Fruit develops in late spring through early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes each contain 15 to 50 fruits (average 20 or so) that are spreading to ascending and crowded on the stalk.

[photo of perigynia front and back, scale and achene] Pistillate scales are egg-shaped to nearly round, translucent white or tinged brown, with a green midrib, blunt or pointed at the tip, sometimes the midrib extending to a very short awn, and are half or less as long as the perigynia. Perigynia are 3 to 4.5 mm long, 1.5 to 2.5 mm wide, green at maturity except yellowish at the base, veinless or obscurely veined, narrowly winged, hairless but with minute teeth along the wing edge on the upper half, not much inflated but spongy at the base, flattened on the back side, generally lance-shaped in outline, widest near the middle tapering to a toothed beak up to 1.2 mm long. Achenes are 1.7 to 2.2 mm long, up to 1.8 mm wide, flattened lens-shaped, and mature to brown.


Carex sparganioides is found primarily in deciduous woods and reaches the northwest tip of its range in the southeast quadrant of Minnesota.

Carex is a large genus, with over 600 species in North America and 150+ in Minnesota alone. They are grouped into sections, the species in each group having common traits. Carex sparganioides is in the Phaestoglochin section; some of its common traits are: clump forming, basal sheaths usually fibrous, sheath fronts cross-wrinkled (rugose), leaves hairless and V-shaped in cross-section when young, 3 to 15 stalkless spikes (rarely the lower are branched), terminal spike with staminate flowers at the tip (androgynous), lateral spikes androgynous or all pistillate, perigynia ascending to spreading and flattened on the back side, rounded and spongy at the base, beaked, the beak usually toothed, flattened lens-shaped achenes.

Carex sparganioides is distinguished by its woodland habitat, loose sheaths cross-wrinkled on the front and green and white striped or mottled on the back, 6 to 15 round to oval spikes, the lowest usually well-separated by twice or more the length of the spike, spikes with 15 or more perigynia that are spreading to ascending, perigynia narrowly winged, flattened on the back side, 3 to 4.5mm long, green at maturity but yellowish at the base, and pistillate scales about half as long as the perigynia. Most similar is Carex cephaloidea, which may be found in a similar habitat but has spikes more crowded at the tip, the lowest separated by less than twice the length of the spike, and spikes with usually fewer than 20 perigynia.

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More photos

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


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Steve Weston - Eagan
on: 2020-09-09 00:00:41

One of about 10 species of Carex in my yard.

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