Carex bebbii (Bebb's Sedge)

Plant Info
Also known as:
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; moist to wet; shores, stream banks, swamps, meadows, forest clearings, swales
Fruiting season:June - July
Plant height:8 to 36 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 spikes] 3 to 14 spikes (usually about 6) each 4 to 10 mm (to 3/8 inch) long, all at the tip of the stem, overlapping and crowded, the inflorescence (group of spikes) erect and up to about 1 inch long. All spikes are stalkless, mostly ascending, usually rounded at both ends, round to egg-shaped to oval in outline, with staminate (male) flowers at the base and pistillate (female) flowers at the tip (gynecandrous). At the base of the lowest spike is a bristle-like bract which is often shorter than the spike, sometimes longer but does not usually rise above the terminal spike.

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

[photo of sheath and ligule] Leaves are alternate with 3 or 4 leaves on the lower third of the stem, up to 12 inches long, 2 to 4 mm wide (rarely more than 3.5 mm), flat, hairless, mostly smooth, and usually shorter than the longest flowering/fruiting stem. Stem leaf sheaths tightly wrap the stem and are mostly green nearly to the tip; the whitish translucent tip extends above the leaf base and is U- to V-shaped across the top edge. The ligule (membrane where the leaf joins the sheath) is longer than wide.

[photo of plant base] Bases are wrapped in a brown sheath, with old leaves often persisting to the next season. Stems are hairless, erect to ascending, 3-sided in cross-section, mostly smooth except just below the spikes. Stems are variable in length and may elongate to about 36 inches at maturity. Plants are clump forming from a mix of vegetative and flowering stems.

Fruit: Fruit type: seed without plume

[close-up of maturing spike] Fruit develops in late spring to mid summer, the spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are mostly ascending and crowded on the spike. Each spike contains numerous fruits.

[photo of perigynia, scale and achene] Pistillate scales are lance to egg-shaped, translucent brown-tinged with a green midrib drying to brown, taper to a pointed tip, 2.5 to 3.5 mm long, somewhat shorter and narrower than the perigynia. Perigynia are 2.5 to 3.8 mm long, 1 to 2 mm wide, light to dark reddish-brown at maturity, hairless, finely veined on the front, veinless or obscurely veined on the back, flattened, not inflated, the body lance-elliptic, rounded to somewhat tapering at the base, tapered to the beak, toothed along the beak edges, and has a wing .2 to .5 mm wide around the edges that extends to the base or nearly so and is commonly obscure until the perigynia dries down. Achenes are lens-shaped, brown at maturity, 1 to 1.5 mm long, .6 to .8 mm wide, narrowly egg-shaped to oblong-elliptic, longer than wide; the distance from the tip of the achene to the tip of the beak is 1.2 to 2.2 mm.

Notes:

Carex bebbii is a common sedge in moist to wet open places in much of the state, found in sandy or gravelly shores, river and stream banks, moist meadows, wet ditches, prairie swales, and the margins of swamps, bogs and occasionally forest openings. It is noted as favoring calcareous soils, but maybe not so much in 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 bebbii is a member of the Ovales section, a notoriously difficult group. Some common traits are: usually clump forming, basal sheaths brown and somewhat fibrous, leaves V-shaped when young; 2 to 20 stalkless spikes all at the stem tip and crowded or not, spikes usually all pistillate at the tip and staminate at the base (gynecandrous), lowest bracts scale-like usually with a bristle tip, pistillate scales blunt to pointed at the tip and sometimes awned; perigynia erect to spreading, hairless, veinless to conspicuously veined on one or both surfaces, flat, beaked, usually with a translucent, papery wing; achenes lens-shaped.

Some traits to look at in Ovales are whether spikes are all crowded at the tip or more loosely arranged, whether the inflorescence is nodding or mostly erect, the shape of the spike (round vs. elliptic vs. club-shaped), the size and shape of the perigynia particularly the body (e.g. round vs. elliptic), the width of the wing and whether it extends all the way to the base, whether there are distinct veins on one or both sides of the perigynia, the length of the pistillate scale relative to the perigynia, the shape of the achene, leaf width, and whether sheaths are papillose, but strong magnification (30x or more) is required to see this. Habitat can also be a factor, and a metric scale is essential since fractions of millimeters make a difference.

Carex bebbii is distinguished from other Minnesota Ovales species by widest leaves less than 4 mm; tight sheaths; 4 to 14 spikes (usually around 6) all crowded together at the stem tip and round to egg-shaped to oval in outline, rounded at both ends, the inflorescence up to about 1 inch long; perigynia 2.5 to 3.8 mm long and 1 to 2 mm wide, finely veined on the front, veinless to obscurely veined on the back, winged to the base or nearly so. The distance from the tip of the achene to the tip of the beak is 1.2 to 2.2 mm. Fruiting stems reach a max height of about 3 feet and it's found in a variety of moist to wet soils, usually in open spaces, less often in part shade. The spikes can turn a dark reddish brown late in the season. The oval to round spikes all crowded at the tip and narrow leaves with tight sheaths are key to an ID.

Carex bebbii has been confused with C. cristatella, which has distinctly loose sheaths, widest leaves more than 4 mm, and the consistently round spikes have more numerous perigynia that are widely spreading and even reflexed. Also similar is C. crawfordii, which has narrower perigynia (.8 to 1.2 mm wide), spikes more elliptic in shape, tapering at both ends, and tends to be a shorter plant, the longest stems 2 feet or less. In my quest to find C. bebbii in the wild, I inspected dozens of potential candidates and nearly all turned out to be C. crawfordii. C. bebbii has been known to hybridize with C. cristatella but I found no records of the hybrid in Minnesota.

While researching C. crawfordii I learned that it and several other North American Ovales have been introduced to Europe and parts of Asia and are becoming invasive there. C. bebbii has been recorded in Sweden since 1980 and central Europe since the 1990s. It is thought to have been introduced as a contaminant in grass seed mixes imported from North America for erosion control of highway embankments (it's sad that they do it, too; hopefully they've discontinued that awful practice).

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More photos

Photos by K. Chayka taken in Becker, Ramsey and Wadena counties.

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