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From afar, it resembles cattail or blue flag iris, but a closer inspection of sweet flag reveals lime-green leaves and finger-like structures that make it easy to identify. The common name refers to the spicy, lime-like fragrance of the sword-shaped leaves when they are cut or bruised. The narrow leaves rise in a fan-like whorl from the base to a height of up to 6'. Sweet flag blooms with 4” spikes of minute, greenish flowers in early to mid-summer. It prefers boggy, wet conditions no more than 2-3” deep, but it tolerates up to a foot of water. The plant needs at least a half day of sunlight and appreciates afternoon shade.  


Sweet flag is found across southern Canada and in the Northeast and upper Midwest, which is the same range as that of the Native Americans who used the plant. It’s believed that these Native Americans helped to widen the range of the plant by using it extensively in ceremonies, medicines, and trade. It’s also found in wet prairies and marsh communities around the Midwest, and it’s a potentially threatened species in Ohio. A. americanus was once a member of the Arum family, but it was recently reclassified to its own family, Acoraceae. Because it’s in the Acorus genus, this freshwater plant is a member of the oldest surviving line of monocots from the ancient world. 


Native habitats include bogs, marshes, and shorelines and water edges (up to a foot of water). Use as an accent or a specimen foliage plant in water gardens. It does well in low spots, woodlands, and naturalized areas as long as a high level of moisture is maintained. 


Plant Characteristics:   

Grows 2-2 ½’ tall and 1-2’ wide. 


Grows in full or part sun. 


Requires moist to wet soils or several inches of standing water. 


A spadix, or cylindrical spike of tiny flowers arranged around a fleshy axis, develops in late spring. The spadix is 1 ½-4” long and contains greenish flowers that give way to dark fruits. 


Bright green leaves are 2-6’ long and about 1 ½” wide with multiple raised veins. Margins are smooth and sometimes wavy. 


Wildlife Value:  

Host plant for the larvae of Plateumaris shoemakeri, a leaf beetle. Other beetles feed on the roots and leaves. Muskrats also feed on the plant. 


Medicinal, Edible, and Other Uses:   

In traditional medicine, the root was powdered and used to treat colic, flatulence, and menstrual cramps.  


The rootstock was used as a natural insecticide and an ingredient of perfumes. 

Sweet Flag, Acorus americanus

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