Carex rostrata (Beaked Sedge)
|Also known as:||Glaucus Beaked Sedge, Bottle Sedge|
|Habitat:||sun; wet sandy or peaty soil; shores, fens, bogs, floating mats|
|Fruiting season:||June - August|
|Plant height:||6 to 36 inches|
|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 4 staminate spikes to 2½+ inches long at the tip of the stem, sometimes with a few pistillate flowers at the tip (gynecandrous) or the base (androgynous) or otherwise mixed. Well-separated from the staminate spikes are 1 to 4 pistillate spikes, occasionally with a few staminate flowers at the tip, each up to 4 inches long, cylindric, 5 to 15 mm (to ~½ inch) in diameter, short-stalked to stalkless, erect to ascending, the longer spikes sometimes nodding. At the base of each pistillate spike is a leaf-like bract; that of the lowest spike is up to 18 inches long, over-topping the terminal spike.
Leaves and stems:
Leaves are basal and alternate, mostly U-shaped in cross-section, the edges often rolled in (involute), the largest leaves 1.5 to 4.5 mm wide (rarely to 7.5 mm), the upper stem leaves often over-topping the terminal spike. Leaves are hairless, mostly erect, the upper surface blue-green to whitish and densely covered in minute bumps (papillose), though 20x or higher magnification is required to see them.
Stem leaf sheaths are concave to U-shaped at the tip, translucent whitish to light brown. The ligule (membrane where the leaf joins the sheath) is as long as or shorter than wide. Bases are wrapped in a brown or sometimes pinkish sheath that is not much fibrous, if at all. Stems are mostly erect, spongy at the base, round to weakly 3-sided in cross-section, smooth, and single or a few together. Stems can elongate up to about 3 feet at maturity. Plants often form large colonies from long, creeping rhizomes.
Fruit develops in late spring to mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are ascending to spreading and tightly packed on the spike. Each pistillate spike contains 20 to 150 fruits.
Pistillate scales are lance to egg-shaped, white to brown tinged to purplish with a pale midvein, pointed or with a long taper to a pointed tip (rarely short-awned), narrower and mostly shorter than the perigynia. Perigynia are 3.6 to 6.5 mm long, 1.6 to 3 mm wide, light green to straw-colored to brown at maturity, hairless, distinctly 9 to 15-veined, thin, inflated, the body lance-elliptic to egg-shaped, broadest near or below the middle, tapering to a smooth beak 1 to 2 mm long that has 2 straight teeth at the tip. Achenes are 3-sided, brown at maturity, elliptic to urn-shaped with a persistent style.
Carex rostrata is an occasional sedge of open, wet areas such as lake and stream margins, fens, bogs and floating mats in north-central and northeastern Minnesota, where it reaches the southern end of its range. It's often found growing in the shallow waters of bog pools and ponds, and forming large stands.
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 rostrata is in the Vesicariae section; some of its common traits are: clump forming or not, rhizomatous, hairless leaves, basal sheaths brown or red-purple, sheaths often splitting into fibers and forming a ladder shape, sheaths with cross partitions between veins (septate-nodulose), 2 to 10 spikes, terminal spike all-staminate, leaf-like bract subtending the lowest pistillate spike, perigynia mostly ascending to spreading, hairless, mostly egg to teardrop shaped, beaked and toothed, at least slightly inflated, achenes 3-sided in cross-section with a persistent style.
Carex rostrata is distinguished from all other Minnesota sedges by the combination of: colony-forming, brown basal sheaths that are not fibrous, round to weakly 3-sided stems smooth below the spike clusters, leaves U-shaped, widest leaves usually 4 mm or less, upper leaf surface densely papillose (20x or more magnification required), 1 to 4 staminate spikes, 1 to 4 cylindric short-stalked to stalkless pistillate spikes, perigynia inflated, 3.6 to 6.5 mm long, distinctly 9 to 15-veined and beaked, 3-sided achenes with a persistent style.
Carex utriculata was once considered a variety of C. rostrata (Carex rostrata var. utriculata) so understandably they are very similar species. Both are colony-forming and may be found in some similar habitats, but C. utriculata tends to be a more robust plant, more green to yellow-green in color, stems are more strongly 3-sided and often somewhat rough just below the spikes, leaves are flat or folded, the widest leaves are usually at least 5 mm, and the upper leaf surface is smooth and usually has distinct cross partitions between the veins (septate-nodulose). By comparison C. rostrata is more blue-green, stems are round to weakly 3-sided and smooth just below the spikes, leaves are U-shaped, the upper leaf surface is papillose, and widest leaves are rarely more than 4 mm. See Michigan Flora for images of microscopic differences between C. utriculata and C. rostrata. Carex vesicaria also has similar spikes as these two but is densely clump-forming, not colony forming. C. rostrata rarely hybridizes with C. utriculata, producing sterile hybrids with intermediate characteristics.
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- Carex rostrata plants
- Carex rostrata plants
- Carex rostrata in shallow water
- spikes with mixed staminate and pistillate flowers
Photos by K. Chayka taken in Aitkin County. Photos by Peter M. Dziuk taken in Aitkin and Lake counties.
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