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Plants of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

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Common Name
Pennsylvania Sedge, (Yellow Sedge, Common Oak Sedge)

 

Scientific Name
Carex pensylvanica Lam.

 

Plant Family
Sedge (Cyperaceae)

Garden Location
Woodland

 

Prime Season
Early to Late Spring

 

Sedge Terms

 

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. Pennsylvania Sedge is a cool season smaller dry-land sedge forming dense clumps. The flowering stems (culms) are triangular in cross-section, 5 to 18 inches high, green in color, usually smooth but the very upper portion may have some weak roughness. These rise singly from the rhizome and there are usually several alternate stem leaves. Bases are reddish.

The leaf blades are alternate along the stem and from the base, mid-green in color, smooth, grass-like, 0.5 to 3.6 mm wide. Base leaves are up 8 to 12 inches long, stem leaves shorter. The surfaces can be a little rough. The leaves arch over such that the leaf clump is rarely more than 8 inches high. In areas without severely cold winters some leaves will remain evergreen. New leaves are surrounded by many older dead leaves.

Leaf sheaths are light green, usually smooth with horizontal veining. The front area of the leaf sheath is V shaped.

The inflorescence consists of both pistillate (female) spikes and a staminate (male) spike above the pistillate ones. There can be 1 to 3 (4) pistillate, either separated or overlapping, and usually only one terminal staminate spike, usually on a short stalk above the pistillate. The inflorescence is subtended by a green bract that is shorter than the inflorescence itself in this species. The male spike is 8 to 24 mm long and 1.3 to 4 mm wide, brown with whitish stamens. The female spikes are much shorter, and have 4 to 13 perigynia. (The bladder-like sacs that enclose the female flower and later the fruit are called perigynia, singular - perigynium).

The perigynia are pale green when immature, ovate in shape, 2.2 to 3.4 mm long, 1.1 to 1.5 mm wide, vein-less, has very fine surface hair and taper to a straight beak of 0.5 to 0.9 mm in length. The scales on the pistillate perigynia are a dark reddish-brown with narrow white margins, ovate in shape, 2 to 4 mm long and 1.3 to 2.8 mm wide, or equaling the perigynium body, including beak, with the scale tips tapered to a point or more obtuse. Staminate scales are elliptic to ovate.

Seed: Female flowers have 3 slender white stigmas and when mature form a dark brown 3-sided achene. Florets are wind pollinated. Achenes need 60 days of cold stratification for germination.

 

Habitat: Pennsylvania Sedge is clump forming with cord-like reddish brown to dark brown horizontally spreading rhizomes. The stolons produced by the rhizomes spread and form plant colonies, which is this species primarily means of regeneration. It can re-seed but seedlings are considered rare and starting plants from seed is difficult. Unlike most sedges, Pennsylvania sedge prefers well drained upland sites with full to partial sun, particularly in the open forest understory and especially near oaks - hence one of the alternate common names - Common Oak Sedge. It has drought tolerance and tolerates shade. In dry shade conditions it will make a nice ground cover but not flower much. This is one of the first sedges to bloom.

Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, pensylvanica, refers to Pennsylvania, the original type location. The name of the author for the plant classification, ‘Lam.’ refers to Jean-Baptiste Lamarck (1744-1829) French naturalist and biologist, an early proponent of evolution who among other things, published the 3 volume Flore Francaise. He is best known for his theory of the inheritance of acquired characteristics.

Comparisons: Pennsylvania Sedge is in the sedge section Acrocystis, characterized by plants with stoloniferous root systems, inflorescences in racemose form with staminate spikes above pistillate spikes, perigynia ascending with a base often spongy and usually beaked and with hair; perigynia scales 1 to 3 veined and rarely awned. Like most sedges, this one has several common names used by various sources. Pennsylvania Sedge is the accepted name used by USDA and USFS and by Minnesota authorities. The sedges in the Large-headed Group similar to C. pensylvanica are C. lucorum and C. heliophila. The first is rare in Minnesota, the second not present. The main difference between C. pennsylvanica and C. lucorum is that in the latter, the beaks of the perigynia are longer, 0.9 to 1.6 mm, and the upper stems are strongly rough surfaces.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Plants drawing

Above: A colony of Pennsylvania Sedge in mid-May growing under Oak Trees. 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: Spikes of Pennsylvania Sedge with one staminate spike at the top and several much shorter pistillate spikes beneath. Last photo - Perigynia maturing.

Inflorescence Spikes with male and female Maturing perigynia

Below: A maturing spike.

mature spike

Below: 1st and 2nd photos - a short stem leaf showing the sheath area. 3rd photo - maturing perigynia.

leaf and sheath ligule perigynia

Below: The reddish base area of flowering stems. Perigynia- note the hairy surface. Photo ©Christopher Noll, Wisconsin Flora.

stem base seeds
Full plant

Below: An early Spring grouping of plants with flowering just beginning.

Spring grouping

Notes:

Pennsylvania Sedge is one of over 150 sedges native to Minnesota. It is quite common across the state with only 9 counties not reporting it. In North America it is found in the eastern half of the continent except for the Canadian Maritime Provinces.

Eloise Butler noted Pennsylvania Sedge growing in the Garden in 1909 and planted it in 1915. It has been noted in the Garden on both the 1986 and 2009 Garden Plant Census. It was most recently planted by Susan Wilkins in 2012.

References and site links

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.

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