The rootstocks of this aromatic plant are used as a natural insecticide and an ingredient of perfumes. They were used by Amerindians for various medicinal purposes, and reportedly induce hallucinations if eaten in sufficiently large quantities. These properties are primarily the result of Alpha-asarone and Beta-asarone; the latter has been found to be carcinogenic. As a consequence, the Food & Drug Administration (FDA) has banned the use of the rootstocks as a food additive. A similar species, Acorus americanus (American Sweet Flag), is restricted to the northern half of North America. It is virtually identical to Acorus calamus (Sweet Flag), except that it has several prominent veins along the length of each leaf. Sweet Flag has a single prominent vein on each leaf that is marked by an off-center ridge/indentation along its length. Another difference is that American Sweet Flag is a fertile diploid that produces fruit with viable seeds. In the past, this species was regarded as a variety of Sweet Flag, and was referred to as Acorus calamus americanus. American Sweet Flag contains Alpha-asraone, but it lacks significant amounts of the carcinogenic Beta-asarone; therefore, it may be safer to use in the preparations that are described above. The Acorus spp. (Sweet Flags) were classified in the Araceae (Arum family) in the past, but they have been reclassified to their own family, the Acoraceae, as a result of recent chromosomal studies.

This native perennial plant is 1-4' tall, consisting of tufts of basal leaves that emerge directly from a spreading rootstock. These basal leaves are erect and sword-shaped, resembling the basal leaves of Iris spp. (Irises), but more green. They are flattened (on one side more than the other), smooth along the margins, and have parallel veins. There is often an off-center ridge/indentation along the length of each leaf. Sometimes the base of the leaves or their margins are slightly red. Some leaves develop a cylindrical spadix that is about 2–4" in length and semi-erect. This spadix is covered with tiny greenish yellow flowers in a diamond-shaped pattern. Each flower has 6 tepals and 6 stamens. The spathe is regarded as absent by some authorities, while others consider the spathe to be a bract-like extension of the basal leaf. The blooming period occurs from late spring to early summer and lasts about a month. Both the crushed foliage and rootstocks have a pleasant aromatic fragrance. Because Sweet Flag is a sterile polyploid species, it doesn't produce any fruit with fertile seeds. The root system consists of shallow branching rhizomes that are stout and knobby; they have a brown exterior and white interior. Tufts of basal leaves occur at intervals along these rhizomes, while coarse fibrous roots develop below. This plant spreads vegetatively by its rhizomes and often forms colonies.

Sweet flag is a perennial, rhizomatous, iris-like herb. The erect, sharp-pointed, sword-shaped leaves fan-out from a pinkish base and grow to 5 feet in length. The midvein is usually off-center. Cut or bruised leaves produce a sweet, tangerine-like scent. The flower stem, or scape, arises from the base of the outer leaves. Although resembling a leaf, the scape is triangular in cross section. A long, erect bract, or spathe, extends beyond the scape. A single, cylindrical 2 to 4-inch spike, or spadex, angles upward at this union. The slightly curved spadix is crowded with small yellowish-green to brown flowers that appear from May to July. Sweet flag has thick, creeping rhizomes with brownish exteriors and white, fleshy interiors.

Calamus

Widespread in Asia (including throughout southern China, Europe, North America, and Russia (Far East, Siberia) (eFloras 2011).

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Global Range: Please see Kartesz (1999) for the updated global range information for Acorus calamus and A. americanus. In North America, A. calamus is mostly concentrated in plains and eastern locations. This species is also reported from Eurasia in the former Soviet Union (Hulten, 1968; Gleason and Cronquist 1963). A. calamus is reported to occur throughout most of the eastern U.S. except Florida, and also in Washington, Oregon, California, South Dakota, Nebraska, Kansas, Oklahoma, and Texas (Kartesz 1999). It is considered an exotic in Ontario (Ontario Natural Heritage Information Centre), Nebraska (Nebraska Natural Heritage Program), Missouri (Missouri Department of Conservation), and Kansas (Kansas Natural Features Inventory). It is historical in Delaware (Delaware Natural Heritage Program) and in Colorado. The Missouri populations were reportedly introduced by settlers for medicinal use (Tim Smith pers. comm.). It is known from seven counties in South Dakota (South Dakota Natural Heritage Database). It is reported from southern lower Michigan (Michigan Natural Features Inventory). It is reported from all counties in Maine (Maine Natural Areas Program).

Packer and Ringius (1984) contains information regarding the taxonomic status and distribution of Acorus in Canada. Only Acorus americanus (A. calamus var. americanus) occurs in Manitoba (Manitoba Conservation Data Centre).

Distribution: N. and C. America, Europe, Asia.

W-E Nepal: Bhutan, China, India, Japan, Sri Lanka; N. Asia, Europe, C. & N. America.

Sweet flag is irregularly circumboreal. In North America it is found from Nova Scotia and Quebec to Minnesota, Alberta and Eastern Washington, south to Florida, Texas and Colorado on wet soils and shallow water in ditches, marshes, river edges and ponds. It prefers full sun and a pH range from 5 to 7.

For a current distribution map, please consult the Plant Profile page for this species on the PLANTS Website.

Sweet Flag occurs occasionally throughout Illinois, although it is less common or absent in the NW and southern areas of the state (see Distribution Map). Habitats include sedge meadows that are prone to flooding, edges of small lakes and ponds, marshes, swamps, seeps and springs, and wetland restorations. Sweet Flag is probably circumpolar in its distribution, occurring as a native species in both North America and Eurasia. However, some authorities regard it as an introduced species that was originally native to India, central Asia, and Eastern Europe. In Western Europe, it can be considered an introduced plant. Because Sweet Flag is usually found in native wetlands, rather than disturbed habitats where weedy plants occur (e.g., roadside ditches), it seems more likely to be a native species. Amerindians may have assisted its distribution in many areas of North America.

Acorus calamus L.:
Afghanistan (Asia)
Bangladesh (Asia)
Bhutan (Asia)
Canada (North America)
China (Asia)
Indonesia (Asia)
India (Asia)
Japan (Asia)
Mongolia (Asia)
North Korea (Asia)
Nepal (Asia)
Pakistan (Asia)
United States (North America)
South Korea (Asia)
Malaysia (Asia)
Russian Federation (Asia)
Sri Lanka (Asia)
Thailand (Asia)
Vietnam (Asia)

Acorus calamus var. verus L.:
Bangladesh (Asia)
India (Asia)
Sri Lanka (Asia)
China (Asia)

Acorus calamus, a sterile triploid, was introduced to North America by early European settlers, who grew it for medicinal uses. Rhizomes propagate easily, and the species has spread throughout northeast and central United States. Scattered populations occur elsewhere. Although leaf and spadix size of A. calamus and A. americanus overlap, those measurements differ significantly, with A. calamus in general having longer and wider leaves and longer spadices.

Perennial herb up to 80 cm tall. Rootstock stout, 1-1.5 cm broad, creeping, with long fibrous roots from the lower surface. Stem erect, glabrous, grooved at one side, and ribbed at the opposite. Leaves ensiform or linear, 55-100 x 8-1.5 cm. Spathe leaf-like, up to 46 cm long, not enclosing the spadix. Spadix 5-6.5 cm long, cylindrical, obtuse, 1-1.4 cm broad. Tepals c. 2 mm long, oblong-obovate, slightly curved, margin membranous, surface with embedded raphides. Filaments 2 mm long, flat, anthers less than 1 mm long, ± orbicular. Ovary 3 mm long, obconical; seeds obconical, 2 mm long,

‘Sweet flag’ is found in marshy places and along river banks from (600-) 1000-2000 m. The rootstock is medicinal and yields an oil used in the manufacture of soap, cosmetics and in the liquor industry; it is also medicinal, being used in stomach complaints, snake bite, as an insect repellant, and for remittent fevers.

100-2300 m

Leaves basally white with pink or red, otherwise bright green; single midvein (secondary midrib) prominently raised above leaf surface, usually somewhat off-center, other veins barely or not raised; cross section rhomboid. Vegetative leaves to 1.75 m; sheathing base (proximal part of leaf) 22.1--66.5(--73.3) cm; distal part of leaf 31.9--95.8(--117.6) ´ 0.5--2 cm, 1.4--1.8 times longer than proximal part of leaf, margins sometimes undulate or crisped. Sympodial leaf (29.9--)34.7--159.1(--183.9) cm, usually shorter than to nearly equal to vegetative leaves; sheathing base 16.1--76.4(--100.1) cm; distal part of leaf 13.5--86.2(--101.2) ´ 0.4--1.9 cm. Spadix (3.8--)4.9--8.9 cm ´ 5.3--10.8 mm at anthesis, post-anthesis spadix 5.5--8.7 cm ´ 6--12.6 mm. Flowers 3--4 mm; pollen grains not staining in aniline blue. Fruits not produced in North America. 2n = 36.

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Depth range based on 4 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 1 - 1
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Shallow waters and wetlands, including ponds, marshes, swamps, and quiet riverbanks or floodplains (Gleason and Cronquist 1963, Fernald and Kinsey 1943). A. americanus is reported to occur in more stable habitats, whereas A. calamus is reported from more disturbed habitats, such as wet pastures and artificial ditches (Swink and Wilhelm 1994).

Flowering early spring--early summer. Wet open areas, marshes, swales, and along edges of quiet water; 0--900 m; introduced; N.B., N.S., Ont., Que.; Ala., Ark., Calif., Colo., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.; Europe; Asia; Africa; Indian Ocean Islands; Pacific Islands.

Sweet Flag occurs occasionally throughout Illinois, although it is less common or absent in the NW and southern areas of the state (see Distribution Map). Habitats include sedge meadows that are prone to flooding, edges of small lakes and ponds, marshes, swamps, seeps and springs, and wetland restorations. Sweet Flag is probably circumpolar in its distribution, occurring as a native species in both North America and Eurasia. However, some authorities regard it as an introduced species that was originally native to India, central Asia, and Eastern Europe. In Western Europe, it can be considered an introduced plant. Because Sweet Flag is usually found in native wetlands, rather than disturbed habitats where weedy plants occur (e.g., roadside ditches), it seems more likely to be a native species. Amerindians may have assisted its distribution in many areas of North America.

Sweet flag can be propagated vegetatively by plant or rhizome division, and by seed. Vegetative propagation is best completed in the fall or spring using firm, healthy rhizomes cut into 2- to 4-inch sections. Plant sections in rich soil 4 - 6 inches deep and 1 foot apart. Separating individual sprigs from clumped plants is an alternative to using rhizomes. These should also be transplanted at 1-foot spacings.

Seed should be planted during the fall or winter in a greenhouse. Fill a 2-inch deep tray with an organic

soil mix, scatter seed sparsely on the surface and press firmly into the soil. Do not bury further than 1/8 inch deep. Keep soil moist to saturated. Seed does not require stratification and germinates in less than 2 weeks. When plants reach 3 to 4 inches transplant into individual 4-inch pots. Pots can be placed in shallow water or irrigated frequently to maintain very moist to saturated conditions. Transplant outdoors 1 foot apart in the spring. With adequate moisture seed can also be planted outdoors spring through early summer, or in a cold frame late summer through fall.

Foodplant / saprobe
immersed pycnidium of Ascochyta coelomycetous anamorph of Ascochyta acori is saprobic on leaf (lower part) of Acorus calamus
Remarks: season: 10-12

In Great Britain and/or Ireland:
Foodplant / spot causer
sparsely scattered, minute, black pycnidium of Ascochyta coelomycetous anamorph of Ascochyta calami causes spots on live leaf of Acorus calamus
Remarks: season: 5-8

Foodplant / saprobe
fruitbody of Endoperplexa enodulosa is saprobic on decayed Acorus calamus

Foodplant / saprobe
Phlyctochytrium planicorne is saprobic on dead stem of Acorus calamus

Foodplant / spot causer
amphigenous pycnidium of Phyllosticta coelomycetous anamorph of Phyllosticta acorella causes spots on leaf of Acorus calamus
Remarks: season: 8

Foodplant / spot causer
amphigenous Ramularia hyphomycetous anamorph of Ramularia aromatica causes spots on live leaf of Acorus calamus
Other: sole host/prey

Muskrats are fond of the rootstocks and readily consume them. Otherwise, little information is available about floral-faunal relationships.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: At least a few hundred North American occurrences for this species known, at least some of which may be native as well as a sizable Eurasian range (cf. Hulten, 1968). "Uncommon" in California (Hickman 1993). There is one population reported from Alaska (Hulten 1968). It is reported to be "not very common" in Nebraska (Nebraska Natural Heritage Program). It is reported to be "common" in Maine (Maine Natural Areas Program). The plant is not rare in New Hampshire (New Hampshire Natural Heritage Inventory). Fourteen occurrences are reported from seven counties in South Dakota (South Dakota Natural Heritage Database). Roughly one hundred occurrences of Acorus are reported from Ontario, including occurrences of both A. calamus and A. americanus (Ontario Natural Heritage Information Centre). Five populations are reported from the Okeefenokee Swamp in southern Georgia, but the taxonomic status of these occurrences is uncertain. Both taxa are genuinely rare in Georgia (Georgia Natural Heritage Program). It is infrequent in marshes, on pond margins, along streams, and in ditches throughout the state of Kentucky (Kentucky Natural Heritage Program). It is reported as common in wetlands across the state of New York (New York Natural Heritage Program). Acorus is common in Indiana in wet fields, ditches, and marshes, but the Indiana NHP has not tried to distinguish the two species of Acorus, and their relative abundance in the state is unknown (Indiana Natural Heritage Data Center). 40 to 50 occurrences are reported from Kansas (Kansas Natural Features Inventory). One occurrence is documented by the Mississippi Natural Heritage Program for the state (Mississippi Natural Heritage Program). A. calamus is rare in Texas with a few wetland occurrences known from the northeastern corner of the state (Texas Natural Heritage Program). It is known historically from three populations in Colorado, all of which appear to have been extirpated. Worldwide, there are probably many thousands of populations.

Fl. Per.: June July.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 21
Species: 34
Species With Barcodes: 1

Canada

Rounded National Status Rank: NU - Unrankable

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: It is likely that this species is in rangewide decline due to the disappearance and degradation of its wetland habitats. The recent splitting of Acorus at the species level means that it is uncertain for many occurrences whether they are A. calamus or A. americanus. When this is sorted out it may become evident that one species is rarer or more common than originally thought.

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).

Population

Population Trend

Major Threats

Comments: An individual with the U.S. herbal medicinal industry states that trade in the plant is modest, on the order of 2000-3000 pounds per year, and that it is the root that is used (McGuffin pers. comm.).

In northeastern South Dakota, the Dakota tribe collects and utilizes an unknown quantity of this plant (David Ode pers. comm.). It is reportedly collected in Canada and the northeastern U.S. for sale on the herb market (Robyn Klein pers. comm.).

Acorus calamus is listed by the United Plant Savers At Risk Forum on their "To Watch" list. This list consists of "herbs which are broadly used in commerce and which, due to over-harvest, loss of habitat, or by the nature of their innate rareness or sensitivity are either at risk or have significantly declined in numbers within their current range." (United Plant Savers 2000)

With the general disappearance and degradation of wetlands, the habitat of this species continues to shrink. Because it is associated with relatively undisturbed habitats when compared with Acorus calamus, A. americanus is probably more threatened in some parts of its range as more undisturbed wetlands become disturbed. Replacement of A. americanus by A. calamus is possible as more wetland habitats become disturbed where the two species overlap. Channelization of springruns has been implicated as a threat to occurrences of this species in Georgia (Tom Patrick pers. comm.). Urban sprawl is causing widespread degradation of potential habitat for this species in southern Lower Michigan (Mike Penskar pers. comm.). Lack of monitoring resources available to properly document the population trends for this species are cited as a threat in Mississippi (Mississippi Natural Heritage Program).

Conservation Actions

Biological Research Needs: The following research projects are needed in order to accurately assess the conservation status of this species: a more complete determination of genetic, physiological, habitat, and range differences between Acorus calamus and A. americanus; a determination the approximate range of this species in North America at the time of initial European contact; and a determination of the degree to which the two taxa are able to hybridize.

Keep soil very moist to saturated; sweet flag does not tolerate droughty conditions. It grows well under seasonal, shallow inundation, however, avoid flooding of newly established plants or seeded areas.

Starter fertilizers may be used indoors to improve early growth but are unnecessary once transplanted outdoors into a rich soil.

The spadix will turn brown as the seed ripens in late summer or early fall. Seed can be planted immediately or stored in low humidity refrigeration.

Rhizomes should be harvested for medicinal use in early spring before new growth, or late autumn. Collect when large and firm, generally after 2 – 3 years of growth, before becoming hollow.

Comments: There are no known differences between the uses for Acorus calamus and A. americanus at this time. This plant has a long history of use by Native Americans, who have used it for a variety of cures. It is used widely by drum singers to help keep the throat moist (Robyn Klein pers. comm.). Small pieces of the plant were sucked while singing during powwows, and it was used as a cough remedy. Native Americans also spread the leaves in their lodgings to give a pleasing scent. Early settlers used the plant as a candy or a kind of throat lozenge (Mike Penskar pers. comm.). It is used by herbalists as a treatment for ailments of the throat and lungs, but only in small amounts as part of an herbal formula (Robyn Klein pers. comm.). It is recommended as a component of formulas for quitting tobacco and marijuana smoking (Tierra 1990). It was probably introduced in many parts of its range by settlers for medicinal use. See Tierra (1990) for a very detailed summary of medicinal applications for this plant.

Euell Gibbons has documented many uses for this plant in his popular books on eating and using plants.

Prices for this species were found as follows:

Unknown location: $4.50/lb (Ed Fletcher pers. comm.)

U.S., internet: $3.25/packet of seeds

U.S., internet: $1.16/oz

U.S., mail order: $8.50/lb of wild-harvested material, $9.50/lb of powdered root

U.S., mail order: $1.08/oz dried root, $8.65/lb (1-4 lbs), $8.20/lb (5-24 lbs), $7.20/lb (25 lbs) (plant material from Poland)

U.S., mail order: $13.49/one-third oz. root essential oil (wholesale), $22.49 (retail)

Cultural Primarily, sweet flag is or was known by the American Indian tribes and early settlers for its medicinal value. Although the preparation of this species and the ailments it treats vary somewhat among the tribes, rhizomes are the most commonly used part.

Wildlife Sweet flag provides habitat for waterfowl. Muskrats eat the rhizomes and wood ducks consume the seed.

The preference is full or partial sun and wet mucky ground or shallow water along shores. This species is semi-aquatic. It is fairly easy to establish from pieces of the rhizome.

Comments: As treated by Kartesz, Acorus calamus excludes the plants sometimes treated as Acorus calamus var. americanus, which (following Thompson, 1995, Ph.D. diss., U.Illinois) is treated by him as Acorus americanus. Kartesz (1999) considers at least some material of both species to be native in North America. LEM 8Jun98 & 14Jun99.

There has been confusion or disagreement as to the native status of this species in North America (Gleason and Cronquist 1963, Great Plains Flora Association 1986, Hitchcock and Cronquist 1976). Kartesz (1999) now recognizes two species (sometimes treated by others as varieties) of Acorus in North America. Under this taxonomy, Acorus americanus is the name given the native North American taxon, while A. calamus refers to the primarily Eurasian taxon, which is also considered native in parts of its present range in North America. Most botanists also consider these two taxa separate; however, there remains a great deal of disagreement about whether A. calamus is native anywhere in North America or not. The two are superficially very similar and difficult to distinguish, but they differ in chromosome number as well as other important characteristics (Michael Oldham pers. comm.). A commonly cited morphological difference between these taxa is the presence of only one raised vein running the length of the basal leaves in the Eurasian taxon, whereas the native North American taxon has two or more such veins (Swink and Wilhelm 1994). As further evidence that these taxa are not conspecific, one herbal remedy guide reports that the Eurasian material contains a carcinogen which North American material lacks (Tierra 1990).

Packer and Ringius (1984) contains information regarding the taxonomic status and distribution of Acorus in Canada.

There remains a great deal of confusion and disagreement among botanists regarding this species. Some Natural Heritage Programs rank this species SE with the assumption that this taxon is entirely exotic in North America. Many reports of Acorus calamus throughout North America probably belong to A. americanus instead.