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. Bur-reed Sedge is a perennial tufted sedge usually found in forest edges and dry to moist woods. The flowering stems (culms) grow 12 to 40 inches high, erect, unbranched with smooth surface except the upper areas may be rough to the touch. Stems narrow in width from 3 to 6 mm wide below to 0.7 to 1.1 mm wide near the top. Roots may put up multiple stems. Stem base have some brownish-purple coloration.
The basal leaf sheaths are longitudinally green and white striped, green and white mottled with cross-veins and translucent rugose fronts. Ligules are 3 to 8 mm long as wide as long.
The upper leaf blades are 5 to 10 mm wide, and up to 8 inches long, V shaped when young otherwise flat, smooth but the edges may be rough on some plants.
The inflorescence is dense with all the spikes somewhat crowded into an elongated head up to 6 inches long. They consist of 5 to 15 spikes, the lowest unstalked. In this species, the lower spikes are distinct, separated by a gap of about 20+ mm - at least 2x as long as the length of the lower spikes. The terminal spike is androgynous, that is, with both staminate and pistillate florets, the staminate at the tip, the pistillate below. The lateral spikes may be androgynous but are usually all pistillate. Each spike can have up to 50 ascending to spreading perigynia. (The bladder-like sacs that enclose the female flower and later the fruit are called perigynia, singular - perigynium).
Each perigynium is pale green in color, vein-less or weakly veined on the back side with a small narrow wing near the top (the wing 0.1 to 0.2 mm wide at the top end), margins rough near the top, without hair, flattened on one face, otherwise rounded, (elliptic to circular) broadest at or just below the middle, roughly 3.3 to 4.3 mm long and 1.5 to 2.5 mm wide. There is a beak 0.8 to 1.2 mm long, with rough margins and 2 tiny teeth. The bracts that form at the base of the spikes are thread-like, with the lower bracts up to 2 cm long. The lowest bract is either without a sheath or with one no more than 4 mm long. The scales of the pistillate perigynia have a translucent appearance with a green mid-vein; these are ovate to sub-circular and mostly less than 1/2 the length of the perigynia and narrower with a pointed tip or short-awned. Scales turn to a light brown at maturity. There are two stigmas per pistillate floret and three stamens per staminate floret.
Seed: Mature fruit is a brown sub-circular shaped achene, about 2 x 1.6 mm, with a short beak at the tip. Florets are wind pollinated.
Habitat: Oval-leaf Sedge grows from a short rootstock without conspicuous rhizomes, forming clumps in dry to wet-mesic deciduous forests, thickets, wood-edges where there is partial shade.
Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, sparganioides, means 'like sparganion' and is the Greek name used by Dioscorides for the Bur-reed. The author names for the plant classifications are as follows: First to publish was ‘Muhl’ which refers to Gotthilf Heinrich Ernst Muhlenberg (1753-1815) American Botanist who produced several catalogues of plants after retiring as a Lutheran pastor. His work was recognized but added to by ‘Willd.’ which refers to Carl Ludwig Willdenow (1765-1812), German botanist, a founder of the study of the geographic distribution of plants. He was director and curator of the Botanic Garden of Berlin.
Comparisons: Bur-reed Sedge is a member of the short-headed bracted sedges in the Section Phaestoglochin, and has the distinguishing characteristics of clustered androgynous spikes containing ascending to spreading perigynia with scales no more that have the length. Another sedge like this with spikes that have a gap between the lower spikes is C. cephaloidea, the Cluster-bracted Sedge, where those gaps, internodes, are not more than 1 cm, less than 2x as long as the lower spikes and the wing on the perigynia is not wider than 1 mm.
Above: Bur-reed Sedge has a noticeable gap between the lower spikes. Note the distinct central green rib on the scales and the two stigmas. 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: The leaf sheath is longitudinally veined with cross-veining, translucent, corrugated front. Blades are V shape when due to the prominent central rib.
Below: The perigynia have whitish-transparent scales with a prominent green rib. The perigynia mature with a thin wing on the otherwise rounded shape. Perigynium photo ©Linda W. Curtis, University of Wisconsin, Steven's Point. 3rd photo - The stem base.
Below: Mature perigynia.
Bur-reed Sedge is one of over 150 sedges native to Minnesota. It is not widespread in the state with only 28 counties reporting it. Most of those counties are in and surrounding the metro area and south-southeast. In North America it is found from the mid-continent eastward, except along the Gulf Coast, in the U.S. and in Ontario and Quebec in Canada.
It has been noted in the Garden on both the 1986 and 2009 Garden Plant Census.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"