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Plant Description


Acorus americanus (Raf.) Raf.

En: American sweetflag, sweetflag, several-veined sweetflag
Fr: belle-angélique, acore d'Amérique, roseau aromatique
Oj: wiikenh.

Acoraceae (Sweetflag Family)

Click on thumbnail to see larger image.
Acorus americanushab Acorus americanusflpl Acorus americanusinf


General: A perennial, aquatic forb, 1.5 m tall, the plant smooth (glabrous), spreading by thick, aromatic rhizomes. The bruised or broken leaves and the cut rhizome give off a strong, pleasant citrus smell.

Leaves: Basal, simple, to 1.5 m long and 1.2 cm wide, 2-ranked, with overlapping bases (equitant); blades linear to sword-shaped, with 2–6 equally prominent, parallel veins. The sheathing leaf bases are whitish, tinged with pink; leaf blades taper gradually to a sharply pointed (acuminate) apex; margins are entire.

Flowers: Bisexual; the numerous, small flowers spirally arranged in a dense finger-like inflorescence (spadix), 3.3–7.5 cm long, that appears lateral on a leaf-like stem. Technically, the spadix is terminal on a flowering stalk (peduncle) that is fused laterally with a taller leaf, thus giving the appearance of the spadix being lateral. Flowers small, 2–3 mm across, with 6 light brown tepals, 6 stamens, and a single, green pistil with a superior ovary and a minute, nearly sessile stigma.

Fruit: The fruiting spadix is only slightly larger and thicker than when in flower; it bears leathery berries with 1–6 seeds.

Habitat and Range: Marshes, margins of ponds and streams. Sweetflag is native to northeastern U.S. and extends across boreal Canada, from southwestern Newfoundland to British Columbia. In Ontario, it occurs as far north as the James Bay coast, near the Moose River.

Similar Species: Acorus calamus, the European sweetflag, can be distinguished by the presence of a single prominent midvein in the leaf. Also, A. calamus is a sterile triploid, so cannot set seed, while Acorus americanus is a fully fertile diploid plant. See this image of Acorus calamus from the Delaware Wildflowers website and this Acorus calamus webpage from the Wetland Wildflowers of Illinois website.

Internet Images: The Acorus americanus webpage, from the Aquatic, Wetland, and Invasive Plants website, from the Univ. of Florida's Centre for Aquatic and Invasive Plants.
The Acorus americanus webpage, from the Robert W. Freckmann Herbarium, Univ. of Wisconsin – Stevens Point.

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