Description
Historically, most American botanists have assumed that a single species of Acorus, 'A. calamus', was present and native in North America, and was identical with the 'A. calamus' of Europe. European A. calamus was introduced from Asia, within historic times (Packer and Ringius 1984). In most large-scale and local floras (e.g. Fernald 1950; Gleason and Cronquist 1991), only a single species of 'A. calamus' is mentioned, and treated as a native. However, it has long been known that European A. calamus were sterile and triploid, while most American Acorus populations produced seeds (Buell 1935; Jervis and Buell 1964; Packer and Ringius 1984; Thompson 1993). These plants are virtually indistinguishable morphologically, but can be distinguished by chromosome examination, or by staining of pollen (Packer and Ringius 1984). The diploid plants have been given the name A. americanus, first proposed by Rafinesque in 1828 (Wilson 1960; Kartesz 1994). While diploid, fertile plants are widespread in North America, sterile plants (true A. calamus) are largely confined to Eastern North America (Packer and Ringius 1984; Thompson 1993). Thompson (1993) found that all of 21 MD specimens examined, collected 1855-1973, and 62 of 64 VA specimens (1892-1989), were A. calamus. Many of the specimens were collected in apparently tidal Bay locations.
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Plantae | Magnoliophyta | Liliopsida | Arales | Acoraceae | Acorus |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1879 | Established | Stable | Introduced | Regular Resident | Europe | East Asia | Ornamental(Garden Escape),Shipping(Dry Ballast) |
History of Spread
Acorus calamus (Calamus) is a sterile, triploid plant native to Asia, which was introduced to Europe in the 16th century (Thompson 1995). Most American botanists have assumed that a single species of Acorus, A. calamus (Sweet-Flag), was present, and did not try to distinguish the sterile form, A. calamus, from the fertile, native A. americanus (Packer and Ringius 1984). Consequently, information on the distribution and abundance of the true A. calamus is limited. In most local floras, information on 'Acorus calamus' may refer to the native A. americanus, unless the species distinction is mentioned. A. americanus is widespread in North America, but sterile plants (true A. calamus) are largely confined to eastern North America (Packer and Ringius 1984; Thompson 1995). Acorus calamus was probably introduced to North America very early, as it was a widely introduced medicinal plant in Europe. The first known herbarium collection is from Philadelphia in 1824 (Thompson 1995).
In Chesapeake Bay, Acorus calamus was probably introduced early and cultivated in settled locations all around the Bay. Of 21 MD Acorus specimens examined by Thompson (1995), all were A. calamus, as were 62 of 64 specimens from VA. Early specimens include ones from Marshall Hall MD (Charles County), on the Potomac River (1895); Spesutie Island MD (Harford County, 1879), Alexandria VA (1894), and Chesapeake City VA (1893) (Thompson 1995). Unverified records of 'A. calamus' have been recorded from all MD fresh tidal tributaries of the Bay (Sipple 1978) and from most counties bordering tidal fresh reaches of Virginia tributaries as well (Harvill et al. 1992). Within the Chesapeake Bay watershed, this plant is found in all 6 states and DC (Thompson 1995).
History References- Harvill et al. 1992; Packer and Ringius 1984; Thompson 1995; Sipple 1978
Invasion Comments
Invasion Status- The USDA Plants database (Natural Resources Conservation Service 1998-2002), while distinguishing A. americanus and A. calamus, calls A. calamus'Native'. We do not know the basis for this, but the designation implies that A. calamus is native to both Asia and North America. Thompson's (1995) extensive herbarium survey appears authoritative to us. Acorus calamus is most abundant near cities and in long-settled areas, while A. americanus is found in wilder places.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-oligo |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 500.0 | 500.0 |
| Typical Adult Size (mm) | 1250.0 | 1250.0 |
| Maximum Adult Size (mm) | 2000.0 | 2000.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Acorus calamus (Calamus) was introduced as widely used medicinal plant, and confection (Fernald and Kinsey 1958), but currently has no economic importance as an herb in our region.
References- Fernald et al. 1958
Economic Impacts Outside of Chesapeake Bay
Acorus calamus (Calamus) was extensively used as a medicinal plant. Candied sweet-flag roots were also a popular confection, 'one of the few frivolities of our great-great-grandmothers' (Fernald et al. 1958).
Ecological Impacts on Chesapeake Native Species
Our knowledge of impacts of Acorus calamus' (Calamus) invasion of the Chesapeake Bay region is hampered by the inability of most botanists to distinguish it from the native A. americanus. A. calamus now appears to be the predominant species of Acorus in the region (Thompson 1993). Most recent records of 'A. calamus' probably refer to the introduced species.
Competition- Replacement of the native Acorus americanus (Sweet-Flag) by A. calamus (Calamus) has apparently been widespread in heavily settled parts of the Eastern US and Canada, but larely unnoticed. In MD, all herbarium specimens examined (n=21, collected 1855-1973) were A. calamus. In VA, 2 specimens of A. americanus were found, the last collected in 1919, while 62 specimens of A. calamus were collected from 1892 to 1989 (Thompson 1995). Competition seems a likely cause for species replacement, but differential responses of species to human disturbance and environmental stresses have not been studied.
Food/Prey- Roots and seeds of both species of Acorus are important as food for muskrats and waterfowl (Thomas 1980; Thompson 1995). However, the effects of replacement of A. americanus by A. calamus have not been studied, to our knowledge.
References- Thomas 1980; Thompson 1995
Ecological Impacts on Other Chesapeake Non-Native Species
Our knowledge of impacts of Acorus calamus' (Calamus) invasion of the Chesapeake Bay region is hampered by the inability of most botanists to distinguish it from the native A. americanus. A. calamus now appears to be the predominant species of Acorus in the region (Thompson 1995). Most recent records of 'A. calamus' probably refer to the introduced species.
Competition- Competitive interactions between Acorus calamus (Calamus) and Iris pseudacorus (Yellow Iris) were studied by Thomas (1980) in marshes on Theodore Roosevelt Island in the Potomac River. Thomas was apparently unaware of the distinction between A. calamus and A. americanus, but based on Thompson's survey of herbarium specimens, these plants were probably true A. calamus. Acorus sp. is expected to succeed I. pseudacorus in many areas of the marsh, but the iris is favored by debris and disturbance, and so is likely to remain on the island in swamp transition area (Thomas 1980).
References- Thomas 1980; Thompson 1993
References
Anderson, Richard D.; Brown, Russell, G.; Rappleye, Robert D. (1968) Water quality and plant distribution along the upper Patuxent River, Maryland, Chesapeake Science 9: 145-156Brown, Melvin L.; Brown, Russell G. (1984) Herbaceous Plants of Maryland, , College Park. Pp.
Buell, M. F. (1935) Acorus calamus in America, Rhodora : 367-369
Fernald, Merritt L. (1950) Gray's Manual of Botany, In: (Eds.) . , New York. Pp.
Fernald, Merritt L.; Kinsey, Alfred C. (1958) Edible wild plants of eastern North America., , New York. Pp. 177-180
Gleason, Henry A.; Cronquist, Arthur (1991) Manual of vascular plants of northeastern United States and adjacent Canada, In: (Eds.) . , Bronx, New York. Pp.
Godfrey, R. K.; Wooten, Jean W. (1979) Aquatic and Wetland Plants of the Southeastern United States: Monocotyledones., In: (Eds.) . , Athens. Pp.
Harvill, A. M.; Bradley, Ted R.; Stevens, Charles E.; Wieboldt, Thomas F.; Ware, Donna M. E.; Ogle, Douglas W.; Ramsey, Gwynn W.; Fleming, Gary P. (1992) Atlas of the Virginia Flora, , Burkeville, VA. Pp.
Jervis, Robert A.; Buell, Murray F. (1964) Acorus calamus in New Jersey., Bulletin of the Torrey Botanical Club 91: 335-336
Jones, Gertrude, E. (1957) Chromosome numbers and phylogenetic relationships in the Araceae., In: (Eds.) . , Charlottesville, Virginia. Pp.
Kartesz, John T. (1994) A synonymized checklist of the vascular flora of the United States, Canada, and Greenland., In: (Eds.) . , Portland OR. Pp.
1997-2024 USDA PLANTS Database.. Onine databse
Packer, John G.; Ringius, G.S. (1984) The distribution and status of Acorus (Araceae) in Canada., Canadian Journal of Botany 62: 2248-2252
Resource Management Inc. (1993) National list of plant species that occur in wetlands., , Minneapolis.. Pp.
Sipple, William S. (1978) An atlas of vascular plant distribution species for tidewater Maryland, , Annapolis, Maryland. Pp.
Thomas, Lindsey Kay (1980) The impact of three exotic plant species on a Potomac island., , Washington, D. C.. Pp.
Thompson, Sue, A. (1995) Systematics and biology of the Araceae and Acoraceae of temperate North America., In: (Eds.) . , Urbana. Pp.
Wilson, Kenneth A. (1960) The genera of the Arales in the southeastern United States., Journal of the Arnold Arboretum, Harvard University 41: 41-72