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Summary
Duration	Perennial
Growth Habit	Forb/herb
U.S. Nativity	Native to U.S.
Federal T/E Status
National Wetland Indicator	OBL
Morphology/Physiology
Active Growth Period	Spring and Summer
After Harvest Regrowth Rate	Moderate
Bloat	None
C:N Ratio	High
Coppice Potential	No
Fall Conspicuous	No
Fire Resistant	No
Flower Color	Yellow
Flower Conspicuous	No
Foliage Color	Green
Foliage Porosity Summer	Dense
Foliage Porosity Winter	Porous
Foliage Texture	Coarse
Fruit/Seed Color	Brown
Fruit/Seed Conspicuous	No
Growth Form	Rhizomatous
Growth Rate	Moderate
Height at 20 Years, Maximum (feet)
Height, Mature (feet)	5
Known Allelopath	No
Leaf Retention	No
Lifespan	Moderate
Low Growing Grass	No
Nitrogen Fixation
Resprout Ability	No
Shape and Orientation	Semi-Erect
Toxicity	None
Growth Requirements
Adapted to Coarse Textured Soils	Yes
Adapted to Fine Textured Soils	No
Adapted to Medium Textured Soils	Yes
Anaerobic Tolerance	High
CaCO3 Tolerance	Medium
Cold Stratification Required	No
Drought Tolerance	None
Fertility Requirement	Medium
Fire Tolerance	High
Frost Free Days, Minimum	90
Hedge Tolerance	None
Moisture Use	High
pH, Minimum	5.2
pH, Maximum	7.2
Planting Density per Acre, Minimum	2700
Planting Density per Acre, Maximum	4850
Precipitation, Minimum	32
Precipitation, Maximum	60
Root Depth, Minimum (inches)	12
Salinity Tolerance	Low
Shade Tolerance	Intolerant
Temperature, Minimum (°F)	-38
Reproduction
Bloom Period	Late Spring
Commercial Availability	Routinely Available
Fruit/Seed Abundance	Low
Fruit/Seed Period Begin	Summer
Fruit/Seed Period End	Summer
Fruit/Seed Persistence	No
Propagated by Bare Root	Yes
Propagated by Bulb	No
Propagated by Container	Yes
Propagated by Corm	No
Propagated by Cuttings	No
Propagated by Seed	No
Propagated by Sod	No
Propagated by Sprigs	Yes
Propagated by Tubers	No
Seed per Pound
Seed Spread Rate	None
Seedling Vigor	Low
Small Grain	No
Vegetative Spread Rate	Moderate
Suitability/Use
Berry/Nut/Seed Product	No
Christmas Tree Product	No
Fodder Product	No
Fuelwood Product	None
Lumber Product	No
Naval Store Product	No
Nursery Stock Product	Yes
Palatable Browse Animal	Low
Palatable Graze Animal	Low
Palatable Human	No
Post Product	No
Protein Potential	Low
Pulpwood Product	No
Veneer Product	No

 

Kingdom  Plantae -- Plants

Subkingdom  Tracheobionta -- Vascular plants

Superdivision  Spermatophyta -- Seed plants

Division  Magnoliophyta -- Flowering plants

Class  Liliopsida -- Monocotyledons

Subclass  Arecidae

Order  Arales

Family  Acoraceae -- Calamus family

Genus  Acorus L. -- sweetflag P

Species  Acorus calamus L. -- calamus P

 

Alternate Names

Calamus

 

Uses

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.

 

Status

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).

 

Description

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.

 

Adaptation and Distribution

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.

 

Establishment

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.

 

Management

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.

 

Prepared By/Species Coordinator:

Tony Bush, Agronomist

Rose Lake Plant Materials Center

East Lansing, Michigan

 

Edited: 05Feb2002 JLK; 30may06jsp

 

For more information about this and other plants, please contact your local NRCS field office or Conservation District, and visit the PLANTS Web site<https://plants.usda.gov> or the Plant Materials Program Web site <https://Plant-Materials.nrcs.usda.gov>

 

 

 

Attribution:  U.S. Department of Agriculture