Sweet Flag (Acorus calamus)

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Sweet Flag (Acorus calamus)

Common Names 

Calamus, Beewort, Bitter Pepper Root, Calamus Root, Flag Root, Gladdon, Myrtle Flag, Myrtle Grass, Myrtle Root, Myrtle Sedge, Pine Root, Sea Sedge, Sweet Cane, Sweet Cinnamon, Sweet Grass, Sweet Myrtle, Sweet Root, Sweet Rush, and Sweet Sedge, Ugragandha, Vach, Vacha, Vaj, Vayambur, Muskrat Root, German Ginger

About This Plant

Sweet Flag is a tall wetland herbaceous perennial monocot that grows to between 1-3 ½ feet tall. Its sword shaped leaves resemble those of Iris plants but are greener and they emit a fragrant odor when crushed. Mature leaves have one slightly wavy edge and a prominent midrib. It has tiny sweetly fragrant greenish flowers that appear in elongated inflorescences which appear in late Spring. In Europe, it flowers for about a month in late Spring or early Summer but does not bear fruit. Its fruit is a berry filled with mucus that when ripe, falls into the water and disperses by floating. In Asia, it also fruits sparingly and propagates itself mainly by growth of its rhizome, forming colonies. It is said that only plants grown in water produce fruits. Sweet Flag has no stem–its leaves rise directly from the rhizome. The branched, cylindrical, knobby rhizome has the thickness of a human finger and has numerous coarse fibrous roots below it.  The exterior is brown with a white interior.


Sweet Flag grows in India, central Asia, southern Siberia, Europe and North America.  Habitats include edges of small lakes, ponds, and rivers, marshes, swamps, and wetlands and often grows alongside Irises, Cattails, and other water weeds. Sweet Flag is semi-aquatic and likes to have “wet feet”, growing in wet, mucky ground and prefers sun but tolerates partial shade, especially in USDA zone 7 and higher. It is hardy to USDA zone 3 and is deciduous, dying down and going dormant every Winter. While preferring boggy conditions, it can be grown in any garden as long as water is provided for it. It cannot tolerate getting dry. It’s a graceful plant for beds and borders and is an excellent choice to brighten shady areas. Its main problem is aquatic animals.  Muskrats love to eat the tubers.


The “sweet” in the name Sweet Flag comes from the sweet aroma the leaves give when broken. It’s been used to flavor wines and herbal bitters. The rhizome is used to make medicine. Sweet Flag was mentioned in the Chester Beatty papyrus VI, dating to approximately 1300 BCE. The ancient Egyptians used it to make perfumes. The plant was introduced to Britain in the late 16th century. Sweet Flag was an item traded by many cultures for centuries.


Many cultures have considered it a sacred plant. It is one of the herbs mentioned in the book of Exodus and one of the ingredients in the ancient biblical anointing oil.  While possessing medicinal qualities, herbalists are more apt to describe what it does for one energetically. Sweet Flag was a favorite of writers Henry David Thoreau and Walt Whitman. Whitman composed a series of “Calamus” poems, which he included in his famous poetry collection “Leaves of Grass”.


Sweet Flag grows readily from the rhizome. Seed should be cold stratified, so direct sow in late Fall and wait until Spring for germination. Or, start stratified seeds indoors in late Winter.  Sow seeds on the soil, pressing them down slightly but not burying them. Plant a few seeds per pot and stand the pots in about one inch of water to ensure they remain constantly moist.  Germination should take about 14 days. Pot up seedlings as soon as they are large enough to handle.  Keep wet and harden off before planting outside.  


After the last frost, transplant starts into full or partial sun and mucky, wet soil, planting slightly below the soil surface. Space plants about 12-24” apart. They will spread their rhizomes to form clumps 1 ½ to 2 feet wide.  If containment is required, plant in containers sunk into wet boggy areas to prevent any invasive spread.


Sweet Flag prefers full sun and boggy conditions but is tolerant of many other growing situations. Provided it doesn’t dry out, Sweet Flag requires almost no additional care or maintenance.  If soils dry out, leaf tips will become scorched. Once established, the plants will grow rapidly and spread out. Sweet Flag can form large colonies in the wild, but are not invasive and can be moved without much difficulty.  After two years, it can be divided for new plantings. Divisions should happen in the Spring to allow the plants to become well established before cold weather.


Rhizomes are usually harvested during their second or third year when they are large enough and still firm.  Older rhizomes tend to become hollow.  The best time to harvest rhizomes is late Autumn or early Spring.  Roots must either be dug from the soil or raked up from ponds and streams.  Fresh rootstock is brownish-red or white-green with a spongy texture.

Leaves can be harvested at any time during the growing season provided they are large enough.  Do not take all the leaves from one plant as it will deplete the rhizome and it may not recover. Keep in mind that since aquatic, Sweet Flag takes up whatever pollutants are in the water, so harvest responsibly.

Seed Harvest

The white or cream colored bracht will turn brown as the seed matures in the late summer or early Fall.  Harvest the brachts when they have ripened fully and spread them out to dry away from direct sunlight.  Rub them lightly to remove the seeds from the stems.  Store seeds in a cool, dry place.

Plant Uses

  • Medicine
  • Flavor for foods, alcoholic beverages, and bitters in Europe
  • Oils valued in the perfume industry
  • Leaves used as a ‘strewing’ herb and placed on the floor to be walked upon during religious rituals and special occasions
  • Wetland gardening
  • Leaves are used to make baskets and woven into mats
  • Powdered root used as a vermifuge and insecticide for fleas, ants, and other insects

Culinary Uses:

Acorus calamus and products derived from A. calamus were banned from use as human food or as a food additive in 1968 by the US Food and Drug Administration due to the presence of beta-isoasarone, a carcinogen, in the rhizomes. The beta-isoasarone content can vary widely among species from 0% to 96% however.  The European Commision, in 2001, established a limit of 115 micrograms per day on consumption. There are multiple varieties of A. calamus–generally speaking, an American, a European, and an Asian variety.  The American variety contains no beta-isoasarone while the Asian variety the most.  These varieties are nearly identical in appearance, however,  and often are misidentified, mislabeled, and missold. Individual medical reports of toxicity mention severe nausea and prolonged vomiting over many hours following oral uses. The ban in the U.S. remains in effect. Despite governmental rulings, Sweet Flag has a long and cherished history of being used as a food source.  Many notable herbalists have weighed in on the Sweet Flag dilemma–of isolating constituents (and giving them in large doses to lab animals) verses moderate use of an unadulterated plant.  Please refer to these practitioners for more insight into the safety of Sweet Flag consumption.


Sweet Flag rhizomes have a sweet aroma and a bitterish, pungent taste. The rhizome  can be peeled and washed to remove the bitterness then eaten like a fruit.  It can also be roasted and used as a vegetable. The root used to be candied and sold as a confection. The dried and powdered rhizome has a spicy flavor and can be used as a substitute for ginger, cinnamon, and nutmeg. The young leaves can be cooked and used as a vegetable or to flavor desserts in the same way vanilla pods are used. The flowers are sweet and can be eaten raw. In Europe, Sweet Flag has a history of being used as a flavor for foods, alcoholic beverages, and bitters.

Medicinal Uses

Sweet Flag has a long history of use for a wide variety of ailments such as GI problems, to induce sweating and for treating pain. It is used as a calming medicine and as a stimulant, bringing the  body’s energy into balance. How can this be? Sweet Flag has an energetic effect on a person that can bring about greater focus, greater resolve and revitalization.  It has been called hallucinogenic. According to herbalist Jim McDonald, while Sweet Flag is psycho-active, it is not psychedelic. In Ayurveda it is highly valued as a rejuvenator for the brain and nervous system. Native Americans have long used this herb, chewing the roots to increase energy and stamina. 


Sweet Flag has been used to assist in quitting smoking. The root and leaves are sometimes put into herbal smoking blends. It has a strong bitter, spicy and aromatic nature and as such, stimulates digestive secretions, peristalsis, and expels gas.  Large doses easily overstimulate the stomach and provoke vomiting. The scent is said to ‘uplift the spirit’ and diffuse “bad vibes”. Sweet Flag was used as an ingredient in ‘flying ointments’. McDonald states, “It teaches us to yield to the flow of things and let go of our needs for stark outlines and delineations.”    


Opinions differ on the origins of Sweet Flag. Probably indigenous to most of Asia, the triploid form Acorus calamus var. Calamus has now been introduced across Europe, Australia, New Guinea, South Africa, and North America. The diploid form of Acorus calamus var. Americanus is found in northern subarctic North America and scattered areas throughout the Mississippi Valley. Diploids are also found in Mongolia, central Siberia, Gilgit-Baltistan in Pakistan, and northern Himachal Pradesh in India. It may not have been native to some of these areas. Pre-Columbian populations are thought to have dispersed it across parts of the United States. It is thought that Native Americans played a role in the distribution of this plant since they likely traveled with and traded it. It has naturalized over time throughout much of the U.S., particularly the northeast and central portions.


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