E-Flora BC: Electronic Atlas of the Flora of British Columbia

Acorus americanus (Raf.) Raf.
American sweet-flag (sweetflag)
Acoraceae (Calamus family)

Introduction to Vascular Plants

© Daniel Stewart  Email the photographer   (Photo ID #71231)

E-Flora BC Static Map
Distribution of Acorus americanus
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Species Information

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Perennial aquatic herb from a thick rhizome; stems 20-60 cm tall.
All basal, linear, erect, 40-80 cm long, 0.8-2 cm wide, the midveins offset.
Inflorescence a dense, fleshy, linear, 5- to 10-cm long spike subtended by a leaflike bract, the bract as long as or longer than the flower stem; flowers perfect; perianth of 6, scale-like, yellow or brown sepals.
Broadly pyramidal, hard, dry, gelatinous within.
Packer and Ringius (1984) have shown that our fertile diploid species is different than the sterile triploid Eurasian species (A. calamus L.) which is introduced in E North America.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Late Spring
Fruit/Seed characteristics:
Colour: Green
Present from Summer to Fall
Source:  The USDA

Habitat / Range

Shallow water in the montane zone; rare in S BC east of the Coast-Cascade Mountains; N to AK and NT, E to PQ and NB and S to ME, PA, VA, IL, IA, NE, MT, ID and WA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Acorus americanus

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 1170 1525 1880
Slope Gradient (%) 0 32 65
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
270 270 270
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
3 3 4
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in:


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Acorus calamus L.
Acorus calamus var. americanus (Raf.) H.D. Wulff.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References