Anthoxanthum hirtum (Sweetgrass)
|Also known as:||Northern Sweet Grass, Vanilla Grass|
|Habitat:||part shade, sun; moist to wet; marshes, sedge meadows, wet prairies, forest edges, wet ditches|
|Fruiting season:||June - July|
|Plant height:||16 to 36 inches|
|Wetland Indicator Status:||GP: FACW MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Open panicle at the tip of the stem, taller than wide, 2 to 6 inches long, pyramidal in outline, the main branches mostly paired at the stem nodes and widely spreading, the lowest branches often slightly drooping. Spikelets (flower clusters) are single at branchlet tips, about ¼ inch (to 6.3mm) long, green usually tinged with purple, somewhat flattened, elliptic to egg-shaped with a pointed tip, each with a single fertile floret flanked by a pair of staminate (male) florets and mostly hidden by them. Branch and spikelet stalks are slender and wiry, green to purple.
At the base of a spikelet is a pair of bracts (glumes) that are thin, translucent around the edge, broadly egg-shaped with a pointed tip, keeled, 1 to 3-veined, 4 to 6.3 mm long, the upper and lower glumes about equal and as long as the spikelet. Surrounding a floret is a pair of bracts (lemma and palea), the lemma hairy especially near the tip and around the edges, the edges wrapping around the floret and mostly hiding the palea. Staminate lemmas are 3 to 5 mm long, elliptic with a point or short awn at the tip, keeled and obscurely 5-veined. Fertile lemmas are egg-shaped, pointed at the tip, 2.9 to 3.5 mm long, without a keel, shiny and usually shorter than the staminate lemma.
Leaves and stems:
Leaves are alternate, flat, hairless and shiny on the lower surface, hairless to finely hairy on the upper surface. Lower and vegetative leaves are 7 to 12 inches long, less than ¼ inch (2 to 5mm) wide, the 2 or 3 stem leaves only 3/8 to 2 inches long and slightly narrower. Stem sheaths are mostly smooth, the edges overlapping near the tip. The ligule (membrane where the leaf joins the sheath) is 2.5 to 5.5 mm long and ragged along the top edge. Basal sheaths may be bladeless. Stems are smooth, single or a few from the base forming loose clumps, unbranched, and typically form colonies from long, creeping rhizomes.
Sweetgrass, formerly known as Hierochloe odorata, is a cool season grass of moist places. The common names come from the vanilla-like fragrance of its leaves, which retain their scent when dried. A showy spring-bloomer, the largish, purplish spikelets on wiry stalks, hairy florets only one of which is fertile, long ligule, typically short stem leaves, and rhizomatous growth are a unique combination.
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Photos courtesy Peter M. Dziuk taken in Cook, Houston, Lake and Polk counties.
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