Anthoxanthum hirtum (Sweetgrass)

Plant Info
Also known as: Northern Sweet Grass, Vanilla Grass
Genus:Anthoxanthum
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
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):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: panicle

[photo of flowering panicle] 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.

[photo of flowering branch and spikelet] 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: Leaf attachment: alternate Leaf type: simple

[photo of sheath, ligule and upper leaf] 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.

Fruit: Fruit type: seed without plume

[photo of spikelet] Fertile florets turn light brown and drop away when mature, leaving the glumes and staminate florets behind persisting on the stalk.

Notes:

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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More photos

Photos courtesy Peter M. Dziuk taken in Cook, Houston, Lake and Polk counties.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: jenifer w - lake bimidji
on: 2017-10-02 22:08:51

its all along the bike path around the lake

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