Carex emoryi (Emory's Sedge)

Plant Info
Also known as: Riverbank Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; wet; river banks, floodplains, ditches, swales, wet woods
Fruiting season:June - July
Plant height:12 to 40 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 clusters] Separate staminate (male) and pistillate (female) spikes, with 2 to 3 staminate spikes up to 2 inches long at the top of the stem. Below the staminate spikes are 3 to 5 pistillate spikes arising singly from the nodes, mostly erect to ascending but may become slightly nodding as they mature; often the pistillate spikes have a few staminate flowers at the tip (androgynous). Pistillate spikes are short-stalked to stalkless, slender and cylindrical, up to 4 inches long, each with a leaf-like bract at the base of the stalk, the bract of the lowest spike not over-topping the terminal spike.

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

[photo of sheath and ligule] Leaves are basal and alternate on the lower stem, 3 or 4 leaves per stem, 3 to 6 mm wide, the upper leaves longer than the flowering stem. Stem leaf sheaths snugly or somewhat loosely wrap the stem, are translucent whitish, thin and fragile, sometimes extending above the leaf base, and are convex to nearly straight across at the tip. The ligule (membrane where the leaf joins the sheath) is wider than long, straight across to convex. Leaves are V-shaped in cross-section when young, and hairless though slightly rough along the edges. Old leaves may persist to the next season before withering away.

[photo of basal sheaths] Bases are wrapped in a brown to reddish-purple sheath that is not fibrous, the lowest sheaths lacking well-developed blades. Stems are 3-sided, single or a few from the base, smooth to slightly rough along the angles, erect to ascending to arching, elongating at maturity but mostly shorter than the leaves. Not all plants produce flowering stems. Plants are not clump-forming but form loose to dense colonies from long, stout rhizomes.

Fruit: Fruit type: seed without plume

[close-up of maturing spike] Fruit develops starting in late spring, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes are densely packed with 50 to 200 fruits, the perigynia mostly ascending and overlapping like shingles.

[photo of perigynia, scales and achene] Pistillate scales are lance-oblong, blunt to pointed at the tip, the edges reddish-brown to purplish-brown with a broad green midvein, lacking awns, and usually narrower than and slightly shorter to slightly longer than the perigynia. Perigynia are green turning straw-colored at maturity, 1.7 to 3.2 mm long, 1 to 2.1 mm wide, 3 to 5-veined on both surfaces, hairless, loosely wrapping the achene, lance-elliptic, usually widest below the middle, tapering to a short, white, toothless beak, and the surface variably whitish granular, especially near the tip. Achenes are 1 to 2 mm long, lens-shaped, brown at maturity.

Notes:

Carex emoryi is a common sedge of river banks, floodplains and wet woods, less often in wet ditches and prairie swales.

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 emoryi is in the Phacocystis section (a combination of former Acutae and Cryptocarpae sections); some of its common traits are: typically clump forming and rhizomatous, leaves V or M-shaped in cross-section when young and hairless except along the edges, spikes long and cylindric, spikes drooping to erect on slender stalks to nearly stalkless, terminal spike usually all staminate or with a few perigynia at the tip, perigynia densely packed, green to brownish, 2-ribbed, weakly veined and short-beaked, achenes lens-shaped with 2 stigmas, growing in wetlands and other wet places.

Carex emoryi is among a group of 5 very similar species in Minnesota; the other 4 are Carex aquatilis, C. haydenii, C. lenticularis and C. stricta. There are a few key characteristics that, in combination, help distinguish them from each other: clump-forming or not, the basal sheaths fibrous or not, the length of the lowest pistillate bract relative to the terminal spike, whether the perigynia is broadest above the middle or not. In some cases, the shape of the ligule, the length of the pistillate scales relative to the perigynia, or other characteristics are also relevant to a correct ID. Most references mention perigynia veins (or lack therof) as an important diagnostic, but we have found these to be pretty obscure in most cases, even under magnification, and sometimes the perigynia base is a bit pleated which might be mistaken for veins.

Of these five species, only C. aquatilis and C. emoryi are colony-forming and not clump-forming. Only C. aquatilis and C. lenticularis have the lowest pistillate bract consistently overtopping the terminal spike. Only C. haydenii and C. stricta have fibrous basal sheaths and form dense hummocks. Only C. aquatilis and C. haydenii should have perigynia widest above the middle, though any of these species may be widest at the middle, at least occasionally. C. aquatilis and C. haydenii have perigynia veinless on both surfaces but veins can be quite faint on the others. Inspect multiple specimens in a population to get a consensus on these traits, and mature specimens are always best though not always available.

C. emoryi is distinguished by the combination of: colony-forming, not clump-forming, basal sheaths not fibrous, the lowest pistillate bract consistently not overtopping the terminal spike, and veined perigynia widest below the middle and tapering to a short, white, toothless beak at the tip, but the most distinctive characteristic is the the tip of the sheath and the ligule both straight across to convex, the ligule distinctly wider than long where the others are at least as long as wide. Pistillate scales are not usually longer than the perigynia but sometimes are.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken along the Rum River in Anoka County.

Comments

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

Posted by: Stephanie Erlandson - Close to the Sibley Historic site.
on: 2020-05-10 16:31:21

This was growing next to the Minnesota River, across from Pike Island, where the Minnesota River joins with the Mississippi. Area was forested, on a floodplain, and recently recovered from flooding. Adjacent to a trail. The plants were blooming. Date: May 10, 2020.

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