Spartina pectinata (Prairie Cordgrass)

Plant Info
Also known as: Sloughgrass, Freshwater Cordgrass
Genus:Spartina
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:sun; moist to dry sandy or loamy soils; shores, swales, marshes, prairies, along railroads,
Fruiting season:August - October
Plant height:3 to 8 feet
Wetland Indicator Status:GP: FACW MW: FACW NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: raceme Cluster type: spike

[photo of flowering cluster] Raceme-like cluster 4 to 20 inches long at the top of the stem, the 5 to 50 branches each 1 to 6 inches long, on short stalks. Branches are mostly erect to ascending, sometimes spreading. Spikelets (flower clusters) are 1/3 to nearly 1 inch (8 to 25mm) long, flattened, oblong-elliptic, and have a single fertile floret. Spikelets are green to purple.

[photo of spikelets] A branch has 5 to 40 pairs of spikelets, arranged on one side of the rachis (stalk), tightly packed in 2 rows. At the base of a spikelet is a pair of bracts (glumes) that are keeled, the keel rough-hairy and extending into an awn, the upper glume lance-shaped and 8 to 25 mm long (including the awn), its awn up to 8mm long; the lower glume is linear and 5 to 10 mm long, 1/3 to about half as long as the upper glume. Florets are surrounded by a pair of bracts (lemma and palea), the lemma lance-shaped with a notched tip, 7 to 10 mm long, awnless, keeled, rough-hairy along the keel and minutely hairy along the edges; the palea is 2-veined and slightly longer than the lemma.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of sheath and ligule] Leaves are mostly on the lower half of the stem, 8 to 36 inches long, about ¼ to ½ inch (5 to 15mm) wide, flat though the edges roll up when dry (involute), the edges very rough textured, the surfaces hairless and smooth. Sheaths have translucent white edging that may or may not overlap near the tip, and are hairless or with a few long white hairs at the tip. The ligule (membrane where the leaf joins the sheath) is a fringe of white hairs 1 to 3 mm long. Stems are erect, hairless, single or a few from the base, typically forming colonies from long rhizomes.

Fruit: Fruit type: seed without plume

[photo of mature spikelet and grain] Spikelets ripen to light brown, the entire spikelet shedding at maturity, leaving a naked rachis behind. Grains (seeds) are oblong and brown, but are often not even formed.

Notes:

Prairie Cordgrass is a common, fast-growing, warm-season grass that has a preference for moist, sandy soil but tolerates a variety of conditions, including dry and saline soils. It's been planted for erosion control and cultivated as a biofuel. It primarily spreads vegetatively, forming clonal colonies, and produces little viable seed, apparently due to insect feeding, possibly combined with the inability to self-pollinate to some degree. The (usually) tall stature, erect to ascending flowering branches with 2 tightly packed rows of awned spikelets make it a pretty distinctive grass, not likely to be confused with other grasses in Minnesota. The related Alkali Cordgrass (Spartina gracilis) is much less common, limited to a few western counties, and is a smaller plant with appressed flowering branches and spikelets that are essentially awnless.

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More photos

Photos by K. Chayka taken in Kittson, Pennington and Pope counties. Photos courtesy Peter M. Dziuk taken in Douglas County, and in North Dakota and Wisconsin.

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