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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: single-vein sweetflag

Synonyms and Other Names: Sweet flag, sway, muskrat root

Taxonomy: available through www.itis.gov

Identification: Acorus calamus is a herbaceous perennial with long erect leaves branching from expansive underground rhizomes (Motley 1994). Leaves are bright green and sword-shaped, base equitant, with wavy margins and have an orange-like smell (Rajput et al. 2014, Mukherjee et al. 2007). Additionally, leaves have a single midvein, slightly raised secondary veins, and many fine tertiary veins which distinguishes it from Acorus americanus (Balakumbahan et al. 2010).

The rhizomes are brownish yellow on the exterior and whitish pink on the interior and exhibit a pleasant aromatic citrus smell and bitter taste (Rajput et al. 2014). Rhizomes are woody and branched, flat to cylindrical in shape, with distinctive nodes and inner nodes (Mukherjee et al. 2007).

Acorus calamus produces cylindrical flowers that arise from the base of the outer leaves (Mukherjee et al. 2007). The inflorescence consists of a leaf-like spathe and a spadix covered in small brownish-yellow flowers (Motley 1994, Mukherjee et al. 2007). The plant produces oblong, angular, green berries that bear few (usually 1-3) seeds (Mukherjee et al. 2007).

Size: Up to 2 m in height, leaves 0.7-1.7 cm wide, flowers are 3-8 cm long (Balakumbahan et al. 2010, Rajput et al. 2014).

Native Range: Acorus calamus is indigenous to east Russia, India and Mongolia to China, Japan, the Korean Peninsula, South-east Asia, Eastern Europe, and much of northern North America (Balakumbahan et al. 2010, Rajput et al. 2014).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Acorus calamus is a semi-aquatic perennial monocot that inhabits littoral eutrophic systems in temperate to subtemperate regions (Dykyjová 1980, Motley 1994). It prefers sandy to clayey loam soils and its shoots spout from a shallow network of underground rhizomes (Dykyjová 1980). Acorus calamus prefers temperatures ranging from 10-38 °C and altitudes of up to 2000 m (Balakumbahan et al. 2010). It grows in depths of 5-45 cm, mostly full sunlight, and A. calamus prefers acidic conditions ranging from 5.6-7.2 pH (Les 2020).

Acorus calamus has “creeping rhizomes” and several emergent shoots can sprout from a single plant connected by an expansive underground rhizome (Motley 1994). Flowers bloom during the summer months, are hermaphroditic, and are pollinated by insects (Balakumbahan et al. 2010, Prajapati et al. 2003; Nadkarni 1998; Wallis 1997). However, no fruiting has been observed in North America (Les 2020).

Muskrats (Ondatra zibethicus) will eat rhizomes of A. calamus, and redhead ducks (Aythya americana) will eat the seeds (Les 2020). Damselflies (specifically Aeshna constricta) will use the A. calamus leaves as oviposition sites.

Means of Introduction: Likely introduced via human activities for medicinal purposes and propagation in herb gardens (Motley 1994). Spread continues through vegetative fragmentation, which can stay buoyant for 6 months (Les 2020).

Status: Established in the western and southern United States (WV, TX, TN, RI, OR, OK, NC, MO, MS, MD, LA, KY, GA, DE, CO, CA, AK, AL), main island of Papua New Guinea, and western and northern Europe (including the UK, Iceland, Svalbard and Jan Mayen). Extinct in Noth Dakota

Impact of Introduction: This plant creates a compact network of underground rhizomes, leading to monoculture stands that prevent the growth and coexistence of other species (Henjý and Husák 1978, Dykyjová 1980). Acorus calamus can be toxic in certain concentrations, causing gastrointestinal issues such as constipation and diarrhea. Thus, in 1968 the U.S. Food and Drug Administration deemed the consumption of A. calamus unsafe (Motley 1994).

Remarks: The leaves, stems, and rhizomes of A. calamus have long been used in traditional medicine, dating as far back as the Romans. Specifically, the ground rhizomes are used to create remedies for a plethora of ailments including gastrointestinal issues, sedation, cough, arthritis, and several neurological and vascular conditions (Balakumbahan et al. 2010, Rajput et al. 2014, Motley 1994, Mukherjee et al. 2007). The leaves have been used on wounds to kill worms (Kapur 1993) and the stems is used to cure coughs and colds (Megoneitso and Rao 1983).

References: (click for full references)

Balakumbahan, R., Rajamani, K. and Kumanan, K., 2010. Acorus calamus: An overview. Journal of Medicinal Plants Research, 4(25), pp.2740-2745.

Dykyjová, D., 1980. Production ecology of Acorus calamus. Folia Geobotanica et Phytotaxonomica, 15, pp.29-57.

Henjý S., Husák S., 1978. Higher plant communities. In: Dykyjová D, Kvet J (eds.) Pond Littoral Ecosystems-Structure and Functioning. Springer-Verlag, New York: pp 23-64.
Kapur, S.K., 1993. Ethno-medico plants of Kangra valley (Himachal Pradesh). Journal of Economic and Taxonomic Botany, 17(2), pp.395-408.

Les, D.H., 2020. Aquatic monocotyledons of North America: ecology, life history, and systematics. CRC Press, Boca Raton, FL.

Megoneitso, Rao, R.R., 1983. Ethnobotanical studies in Nagaland-4. Sixty two medicinal plants used by Angami Nagas. Journal of Economic and Taxonomic Botany, 4(1), pp.167-172.

Motley, T.J., 1994. The ethnobotany of sweet flag, Acorus calamus (Araceae). Economic botany, pp.397-412.

Mukherjee, P.K., Kumar, V., Mal, M. and Houghton, P.J., 2007. Acorus calamus.: scientific validation of ayurvedic tradition from natural resources. Pharmaceutical biology, 45(8), pp.651-666.

Nadkarni, K.M., 1998. Indian Materia Medica, 1st ed. Popular Prakashan, India.

Prajapati, N.D., Purohit, S.S., Sharma, D.D., Tarun, K., 2003. A Handbook of Medicinal Plants, Section II, 1st ed. Agrobiaos, India.

Rajput, S.B., Tonge, M.B. and Karuppayil, S.M., 2014. An overview on traditional uses and pharmacological profile of Acorus calamus Linn.(Sweet flag) and other Acorus species. Phytomedicine, 21(3), pp.268-276.

Wallis, T.E., 1997. Textbook of Pharmacognosy, 5th ed. CBS Publication, India.

Author: Reaver, K.M.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.