Carex haydenii (Hayden's Sedge)
|Also known as:
|sun; wet; prairies, meadows, marshes
|June - August
|Wetland Indicator Status:
|GP: OBL MW: OBL NCNE: OBL
|MN county distribution (click map to enlarge):
|National distribution (click map to enlarge):
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Separate staminate (male) and pistillate (female) spikes, with 1 to 3 staminate spikes up to 2 inches long at the top of the stem. Below the staminate spikes are 3 to 5 erect to ascending pistillate spikes arising singly from the nodes; occasionally the pistillate spikes have a few staminate flowers at the tip (androgynous). Pistillate spikes are short-stalked to stalkless, slender and cylindrical, up to 2 inches long, each with a leaf-like bract at the base of the stalk, the bract of the lowest spike rarely over-topping the terminal spike.
Leaves and stems:
Leaves are basal and alternate on the lower stem, 2 to 4 leaves per stem, 2 to 5 mm wide, the upper leaves not usually overtopping the flowering stem. Stem leaf sheaths snugly or somewhat loosely wrap the stem, are translucent whitish, thin and fragile, and are concave to nearly straight across at the tip. The ligule (membrane where the leaf joins the sheath) is as long as or longer than wide, pointed at the tip with loose tissue around the edge. Leaves are M-shaped in cross-section when young, and hairless though slightly rough along the edges.
Bases are wrapped in a brown to reddish-purple sheath that is usually finely fibrous, sometimes the fibers forming a weak ladder pattern, and the lowest sheaths lacking well-developed blades. Stems are 3-sided, smooth to slightly rough along the angles, erect to ascending to arching, elongating at maturity and mostly rising above the leaves. Not all plants produce flowering stems. Plants are clump-forming, the old leaves persisting and forming dense hummocks. Large stands are common.
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 25 to 100 fruits, the perigynia ascending to spreading, and overlapping like shingles.
Pistillate scales are lance-elliptic, mostly pointed at the tip, the edges reddish-brown to purplish-brown with a narrow green midvein, lacking awns, and narrower and consistently longer than the perigynia. Perigynia are green turning golden or olive brown at maturity, 1.5 to 2.8 mm long, 1.2 to 2 mm wide, veinless, hairless, inflated and loosely wrapping the achene, elliptic to nearly round, widest at or above the middle, rounded at the tip with an abrupt taper to a minute, toothless beak, and the surface minutely red-dotted on the upper half. Achenes are about 1 mm long, lens-shaped, nearly round in outline, brown at maturity.
Carex haydenii is a sedge of open, wet places such as meadows, marshes and prairie swales, less often on shores and river banks, and usually in sandy soil.
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 haydenii 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 haydenii is among a group of 5 very similar species in Minnesota; the other 4 are Carex aquatilis, C. emoryi, 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. haydenii is distinguished by the combination of: clump-forming, forming dense hummocks, basal sheaths weakly fibrous, the lowest pistillate bract consistently not overtopping the terminal spike, pistillate spikes up to 2 inches long, veinless perigynia plump and inflated at maturity, widest at or above the middle and mostly rounded at the tip, and pistillate scales consistently longer than the perigynia. It most closely resembles C. stricta, which is the only other species of this group that forms dense hummocks, but its basal sheaths are strongly ladder-fibrous, leaves more often rise above the flowering stems, pistillate spikes can be longer (up to 4 inches), and the perigynia are somewhat larger, more flattened, tapering at the tip and usually widest below the middle.
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- Carex haydenii plant
- Carex haydenii plants
- Carex haydenii plants
- plants form dense hummocks of old leaves
- flowering stems rising above the leaves
- pistillate spikes sometimes have a few staminate flowers at the tip
- more spikes
- immature perigynia, widest above the middle
Photos by K. Chayka and Peter M. Dziuk taken in Anoka, Brown and Fillmore counties. Photos courtesy Steve Eggers taken in Aitkin County.
Have you seen this plant in Minnesota, or have any other comments about it?