Acorus calamus

Sweet Flag

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Sweet flag is a wetland species in the arum family resembling cattails or sweet flag iris, with narrow, rigid leaves up to three feet tall. The leaves have ridges and the bases have a red tinge. The flower is a curious little yellow-green spike (called a “spadix”). It shoots out at an angle from a stem that looks the same as the leaves. It appears in early summer and may not even be noticeable among the leaves. The rhizomes have a sweet fragrance when crushed and have been used in folk medicine. Muskrats are fond of eating the rhizomes. While the species is found in wetlands all over the northern hemisphere, there are different genetic strains, and with cultivation, strains from Europe have been flourishing in Eastern North America. They can only be distinguished from the natives by the number of veins in the leaves.

Plant Shape
Full Sun, Partial Shade
Bloom Time
May - June, July - August
Bloom Color
Yellow, Green
Landscape Use
Specimen Plant
Wildlife Interest
Native to Midwest
Plant Type
Hardiness Zone
4 - 10