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. Common Hop Sedge is a native perennial loosely tufted sedge preferring a moist environment. The flowering stems (culms) are smooth and grow 8 to 40 inches high, singly or a few stems in a clump.
Leaf Sheaths: Basal leaf sheaths are persistent, reddish to brownish in color. Upper sheaths are green with a long split front side. Ligules are triangular, 3.5 to 18 mm long (longer than wide).
The leaf blades are 4 to 15 mm wide and fairly long - 15 to 64 cm long (6 to 25 inches). There are 4 to 8 per stem. Upper blades are longer than the inflorescence and usually rise above it before arching over. Blades have a central channel and two parallel lesser channels creating a "M" shape in cross-section.
The inflorescence at the top of the stem has multiple spikes, 4 to 40 cm (to 15 inches) in total length. There are 2 to 5 lateral spikes on the lower section of the inflorescence that are pistillate. These are stalked with the lower 2 spikes separated by a short gap. The upper pistillate spikes are ascending, ovoid to cylindric in shape and densely crowded and densely flowered with 8 to 80 flowers. Each pistillate spike can be 1.5 to 6.5 cm long, and thick - 1.3 to 3 cm wide. The terminal spike is a single stalked staminate spike (although 2 may occur). The staminate spike is very thin, only 1 to 5 mm wide and is 1.5 to 8.5 cm long. Once flowering occurs, it turns brown and withers quickly. Each pistillate spike has perigynia that are elongated ovoid in shape, ascending and densely packed on the spike. (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 lower spikes are leaf-like and long - 13 to 55 cm long, slightly longer than the length of the inflorescence. These have sheaths.
Each perigynium is strongly 13 - 22 veined, smooth shiny surfaced with the body gradually tapering to a conic beak 6 to 10. The body of the perigynium is roughly 11 to 19 mm long and 3 to 6 mm wide. The appearance is swollen and bladder like with a spiky tip. The scales of the pistillate perigynia are more than half the length of the perigynium, 1 to 7 green veined, lanceolate to ovate in shape, with a pointed apex and usually with a rough awn of up to 6 mm. There are three stigmas per pistillate floret.
Seed: Mature fruit is a brown elongated achene, (basically 3-angled) with flat to concave faces and a persistent style. The angles of the achene are smoothly thickened, not pointed or knobbed. Each is about 3.0 to 4 mm long by 1.7 to 2.6 mm wide. Florets are wind pollinated. Carex achenes usually require 60 days of cold stratification for germination - or sown outside in the Fall.
Habitat: Hop Sedge grows from a base of short rhizomes, in wet to wet-mesic conditions such as in marshes, alder thickets, wet and open thickets, sedge meadows, fens, and particularly alluvial soils. Plants prefer full sun but will grow in partial sun to shade. It usually does not form colonies.
Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, lupulina, means 'hoplike' referring to the bladder-like perigynia that can resemble the clusters of various hop plants. The author name for the plant classification - ‘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: Hop Sedge is a member of the sedges in the Section Lupulinae, which have the distinguishing characteristics of usually not forming colonies, stems purplish to reddish at the base, basal sheaths not fibrous, wide V to M -shaped leaf blades, raceme type inflorescences with multiple spikes, upper spikes staminate and lower spikes pistillate, lower bracts leaflike, 3 stigmas per floret. The sedges in this section have the largest perigynia of any Carex.
The most similar sedge like Hop Sedge is C. lupuliformis, the False Hop Sedge (drawing below), where the main difference is in the achenes - which have hard knoblike points. However, C. lupuliformis is not found in Minnesota and only rarely in Wisconsin. The sedge in our area that is most confusing is C. grayi, the Gray's or Bur Sedge which is found in similar habitats to Hop Sedge. There the noticeable differences are the beak of the perigynia is shorter and the perigynia radiate out in all directions rather than be ascending. This makes the spike appear mostly globular rather than cylindric. The distribution however, is more restricted - usually to the SE section of Minnesota and that plant is on the DNR's "Special Concern" list.
Above: The tall erect inflorescence is exceeded in length by the upper leaves. 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 single staminate spike rises above the lower pistillate spikes. 2nd photo - staminate spike flowers. 3rd photo - pistillate spike flowers.
Below: 1st photo - The long, split leaf sheath. 2nd photo - "m" shaped leaf blade.
Below: 1st photo - pistillate perigynia. 2nd photo - basal sheaths are reddish in color.
Below: The root system and basal sheaths.
Below: 1st photo - a mature perigynium with too short beaks. photo ©Linda Curtis, Wisconsin Flora. 2nd photo - Achenes showing the rounded and smooth angles and persistent style. Photo ©Steven Hurst, USDA-NRCS Plants Database.
Below: A comparison of the spikes, perigynium and achenes of some of the sedges from Sect. Lupulinae that are referenced in the "comparison notes" above. Drawing courtesy and ©Flora of North America
Below: Carex lupulina. Note the long bracts from the base of the pistillate spikes.
Hop Sedge is not present in the Wildflower Garden. The species is found in the eastern half of North America with Minnesota and Ontario being at the northwest part of the range, then south along the Mississippi River States as the western edge of the range. Within Minnesota it is concentrated on the eastern half of the state, absent in the west and southwest. In the metro area it is known in Carver, Hennepin, Dakota, Ramsey, and Washington Counties. It is is one of over 150 sedges native to Minnesota.
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"