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. Eastern Star Sedge is a perennial tufted sedge usually found in forest edges and mesic to moist woods. The flowering stems (culms) grow 8 to 30 inches high, erect until mid-summer when they sprawl, unbranched with smooth surface except the upper areas may be rough to the touch. Stems are exceedingly narrow in width from 0.8 to 1.5 mm wide below to 0.4 to 0.5 mm wide near the top. Roots may put up multiple stems. The base of the stems is brown.
The basal leaf sheaths are tight and green with whitish-translucent fronts. Ligules are less than 2 mm long, wider than long.
The widest leaf blades are grass-like, only 1.3 to 1.9 mm wide, a rounded V shaped when young otherwise flat, smooth but the edges may be rough on some plants. In warmer parts of the plants range the leaves will be evergreen.
The inflorescence has the spikes separated at the top of the stem with the gap between the lower spikes being more than 2x the length of the lower spikes. There are 4 to 8 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 are usually all pistillate. Each spike can have 3 to 8 spreading or reflexed perigynia - creating a star shape in the spike which gives the common name. (The bladder-like sacs that enclose the female flower and later the fruit are called perigynia, singular - perigynium). The bracts that form at the base of the spikes are thread-like, with the lower bracts up to 5 (10)cm long, but less than 2x the length of the entire inflorescence. The lowest bract is either without a sheath or with one no more than 4 mm long.
Each perigynium is green in color, vein-less, the base of the body spongy and thickened, the spongy part not more than 20 to 30 % of the perigynium length, the back side with longitudinal striations, the margins near the top finely serrate, ending with a beak 0.4 to 1.0 mm long with a pair of pointed teeth. The body of the perigynium is roughly 2.6 to 3.8 mm long and 1 to 1.5 mm wide (1.5 to 3x as long as wide). The scales of the pistillate perigynia have a translucent appearance with a green mid-vein; these are ovate and mostly 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 which are straight or slightly twisted to only slightly coiled (which gives one of the common names - Straight-styled Wood Sedge); and three stamens per staminate floret.
Seed: Mature fruit is a brown ovate to obovate shaped (basically 2-sided) achene, about 1.5 to 2.0 mm long x 1.0 to 1.4 mm wide (not more than 2x as long as wide). Florets are wind pollinated.
Habitat: Eastern Star Sedge grows from a short rootstock without conspicuous rhizomes, forming clumps in mesic to wet-mesic deciduous forests, thickets, wood-edges and other moist edges where there is partial shade to full shade. Avoid full sun and keep moist.
Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, radiata, means 'with radiating form' and refers to the position of the perigynia and the achenes pointing outward from the point of attachment. The author names for the plant classification are as follows: ‘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. His work was amended by ‘Small’ which refers to John Kunkel Small (1869-1938), American Botanist, first curator of the New York Botanical Garden, best known for Flora of the Southeastern United States. The common names are explained above other than that 'eastern' is used to differentiate this species from the other starry sedge, C. rosea, which has a wider distribution westward and southward in North America.
Comparisons: Eastern Star 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 half the length of the perigynia body. The most similar sedge like this is C. socialis, the Low-woodland Sedge, the only real difference is the perigynia are 3 to 5x as long as wide and the achenes are more than 2x as long as wide. However, C. socialis is not found in our area, only in the southern states. The sedge in our area that is most confusing is C. rosea, the Stellate (or Rosy) Sedge. There the only real noticeable difference, without magnification, is that the sigmas are definitely coiled (looking like Ram's horns), the spongy part of the perigynium is only 20% of the perigynium length. These are very fine distinctions and confuse the experts unless you study a number of plants and plant parts over the growing season. Seeing the plants when the stigmas are fresh is the best distinction. Also C. rosea prefers a less moist environment.
Above: The lower spikes are widely spaced on the stem. Drawing ©Kenneth Kent Mackenzie (1940) North American Cariceae, Illustration by Harry Charles Creutzburg.
Below: The perigynia number 3 to 8 in a spike and are spreading to reflexed. Leaf sheaths have translucent fronts and small ligules. The blades are very narrow - up to 1.9 mm wide.
Below: 1st photo - leaf - center rib forms a V shape. 2nd photo - the inflorescence in the flowering stage.
Below: 1st photo - the staminate spike at the tip. 2nd photo - the two lowest pistillate spikes - note the thread-like bract and the styles that are fairly straight with little twist to them.
Eastern Star Sedge is one of over 150 sedges native to Minnesota. It is widespread in the state with most of the counties not reporting it in the drier SW quadrant. In North America it is found from the Central States eastward in the U.S. (excluding those along the Gulf Coast and several interior southern states such as Oklahoma and Tennessee), and in Canada from Manitoba eastward to the coast except for Newfoundland.
Eloise Butler reported discovering C. radiata in the Garden on May 31, 1916. In her day the accepted classification was Carex stellulata (full name Carex stellulata Gooden. var. radiata) which is now considered a synonym for C. radiata. It was missed on both the 1986 and 2009 Garden Plant Census but now reported on a recent sedge 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"