Sedges differ from grasses by having a 3-angled stem and structurally different flowers where the female flowers are enclosed in a sac like structure called the perigynium, which is subtended by a single scale. Narrow-leaf Sedge is a native perennial densely tufted sedge commonly forming tussocks (or hummocks). The flowering stems (culms) grow 6 to 35 inches high. The lower 2 to 3.2 cm of the culm is dark purple-red, rarely brown.
The leaf sheaths on the front are smooth with membranous fronts, the basal sheaths not fibrous. Ligules are delta shaped, 3 to 7.5 mm long, longer than wide.
The leaf blades are fairly wide for a sedge, 4.2 to 8.3 mm wide, but short, only up to 7 inches long. There are 1 to 3 per flowering stem. Blades are slightly M shaped when young with two lateral veins more prominent than the midrib.
The inflorescence is in racemose form, flexible and consists of usually 4 to 5 spikes, the upper 2 to 4 usually overlapping. All spikes have short stalks. The terminal spike is staminate, 7 to 35 mm long and 1.5 to 3.1 mm wide, placed adjacent to and barely exceeding the upper lateral spike. Laterals are usually all pistillate but can occasionally be androgynous, that is, with the staminate and pistillate florets on the same spike, with the fewer staminate florets above. Lateral spikes are 5 to 31 mm long and 6.7 to 11.4 mm wide. The bract that forms at the base of the lower spike is leaf like with a sheath that is smooth. The bract of the upper lateral spike usually exceeds the terminal spike in length.
The perigynia are erect to ascending, green in color, narrowly ellipsoid to obovoid in shape and rounded in cross-section, inflated (orbicular) - and 4.5 to 5.1 mm long and 2 to 2.6 mm wide (about 1.8 to 2.3 times as long as wide), and number 3 to 19 per spike in a ratio of spike length to perigynium number of 1.6 to 2.1. (The bladder-like sacs that enclose the female flower and later the fruit are called perigynia, singular - perigynium). The perigynium itself densely 52 to 64 veined, not wrinkled, shiny, with a base and tip gradually tapered. A beak on the tip may be absent or if present, it is straight. The scales of the female spikes are white membranous on the margins, usually with red-brown speckles and a green central area, tapering to an apex with a long, 0.9 to 5.3 mm long awn. These can be longer than the perigynia and as wide, 4 to 8.2 mm long and 2.1 to 2.6 mm wide. There are three stigmas per flower, 3 stamens.
Seed: Mature fruit is a brown broadly obovoid shaped 3-angled achene 3.1 to 3.5 mm long and 1.7 to 2.1 mm wide, loosely enclosed by the perigynium with a straight beak (the awn) which drops away. Florets are pollinated by the wind.
Habitat: Narrow-leaf Sedge grows from a rhizomatous root system forming dense tussocks, not colonies, in moist woodland areas, woodland opening and flood plains. The species handles wet to mesic moisture conditions, grows in full sun if in wet conditions otherwise it grows also in partial sun to shade in wet-mesic to mesic areas.
Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, grisea, means 'gray'. The author name for the plant classification - ‘Wahlenb.’ refers to Georg Wahlenberg (1780-1851) Swedish naturalist, professor of botany and medicine at Uppsala University. His work focused on plant taxonomy and geography, one of the first to do so. A major work was Flora lapponica. The common names given to this sedge over time leave much to be desired. As sedges go, this species is not narrow-leaved and the leaves are not gray. Ambiguous Sedge may be the best as it is often confused with C. amphibola as explained below.
Comparisons: Narrow-leaf Sedge is classified in the sedge section Griseae wherein the species form dense clumps from short to long rhizomatous root systems, have staminate terminal spikes and pistillate to sometimes androgynous lateral spikes on racemose inflorescences with bracts leaf-like. Perigynia are erect to spreading, usually smooth surfaces, rounded, tapering on both ends with an abrupt beak or none at all. Achenes are smaller than the perigynia bodies, 3 angled, with a long pointed tip.
C. amphibola, also called Narrow-leaf Sedge, has just slightly smaller leaves and a similar inflorescence. There are slight differences in size of all elements and careful measurements must be taken to distinguish species. The most noticeable differences are that C. amphibola has perigynia obtusely triangular in cross-section, 2.5 to 3.1 times as long as wide, 1.5 to 1.9 mm wide vs 2 to 2.6 mm in C. grisea. Also the achenes of C. amphibola are not as wide. C. amphibola is not considered as an accepted species to be present in Minnesota by the DNR and the U of M Herbarium.
Above: 1st photo - the inflorescence. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - the Staminate spike atop the stem with pistillate spike below. 2nd photo Perigynia with old staminate spike adjacent.
Below: 1st photo - stem bases are usually reddish-purple. 2nd photo - leaf blades have a mid-vein and two veins with an opposite fold creating an "M" shape.
Narrow-leaf Sedge is one of over 150 sedges native to Minnesota where it is found in the southern half of the state with some exceptions being mostly counties in the SW. In North America it is found in the eastern parts of Canada and in the U.S. from the central plains S. Dakota down to Texas, then eastward to the coast except for Florida, Alabama, Georgia, and the Carolinas.
Narrow-leaf Sedge has been listed on both the 1986 and 2009 Garden Census as C. amphibola, but as explained above that name in Minnesota should defer to C. grisea.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"