Sweet flag has a long history of medicinal use in herbal traditions.  Is widely employed in modern herbal medicine as an aromatic stimulant and mild tonic.

In Ayurveda, it is highly valued as a rejuvenator for the brain and nervous system and as a remedy for digestive disorders.

However, some care should be taken in its use since some forms of the plant might be carcinogenic – see the notes above on toxicity for more information.

Medicinal use of Sweet Flag

The root is anodyne, aphrodisiac, aromatic, carminative, diaphoretic, emmenagogue, expectorant, febrifuge, hallucinogenic, hypotensive, sedative, stimulant, stomachic, mildly tonic and vermifuge.

It is used internally in the treatment of digestive complaints, bronchitis, sinusitis etc. It is said to have wonderfully tonic powers of stimulating and normalizing the appetite. In small doses, it reduces stomach acidity whilst larger doses increase stomach secretions and it is, therefore, recommended in the treatment of anorexia nervosa.

However, if the dose is too large it will cause nausea and vomiting. Sweet flag is also used externally to treat skin eruptions, rheumatic pains, and neuralgia. An infusion of the root can bring about an abortion whilst chew the root alleviates a toothache.

It is a folk remedy for arthritis, cancer, convulsions, diarrhea, dyspepsia, epilepsy etc. Chewing the root is said to kill the taste of tobacco. Roots 2 – 3 years old are used since older roots tend to become tough and hollow. They are harvested in late autumn or early spring and are dried for later use.

The dry root loses 70% of its weight but has an improved smell and taste. It does, however, deteriorate if stored for too long. Caution is advised on the use of this root, especially in the form of the distilled essential oil, since large doses can cause mild hallucinations.

See also the notes above on toxicity. A homeopathic remedy is made from the roots. It is used in the treatment of flatulence, dyspepsia, anorexia, and disorders of the gallbladder.

Description of the plant


100 cm (3 1/4 foot)

May to July

Scented Perennial

The habitat of the herb

Found in moist soils and shallow water in ditches, marshes, river edges, and ponds.

Edible parts of Sweet Flag

The rhizome is candied and made into a sweetmeat. It can be peeled and washed to remove the bitterness and then eaten raw like a fruit.

It makes a palatable vegetable when roasted and can also be used as a flavoring. Rich in starch, the root contains about 1% of an essential oil that is used as a food flavoring.

The root also contains a bitter glycoside. Some caution is advised, see the notes above on toxicity. The dried and powdered rhizome has a spicy flavor and is used as a substitute for ginger, cinnamon, and nutmeg.

A pinch of the powdered rhizome is used as a flavoring in tea. The young and tender inflorescence is often eaten by children for its sweetness. Young leaves – cooked. The fresh leaves contain 0.078% oxalic acid.

The leaves can be used to flavor custards in the same way as vanilla pods. The inner portion of young stems is eaten raw. It makes a very palatable salad.

Other uses of the herb

The leaves are used in basket making or woven into mats. They have also been used as a thatch for roofs. An essential oil from the rhizome is used in perfumery and as a food flavoring.

The oil is contained mainly in the outer skin of the root, it has a fragrance reminiscent of patchouli oil. The fresh roots yield about 1.5 – 3.5% essential oil, dried roots about 0.8%. Some plants from Japan have yielded 5% essential oil.

The essential oil is also an insect repellent and insecticide. It is effective against houseflies. When added to rice being stored in granaries it has significantly reduced the loss caused by insect damage because the oil in the root has sterilized the male rice weevils.

An essential oil obtained from the leaves is used in perfumery and for making aromatic vinegar. The leaves and the root have a refreshing scent of cinnamon. All parts of the plant can be dried and used to repel insects or to scent linen cupboards.

They can also be burnt as an incense, whilst the whole plant was formerly used as a strewing herb. The growing plant is said to repel mosquitoes.

Propagation of Sweet Flag

Seed – best sown in a cold frame as soon as it is ripe. Stand the pot in about 3cm of water. Pot up young seedlings as soon as they are large enough to handle, keep them wet by standing the pots in shallow water and overwinter for the first year in a greenhouse or cold frame.

Seed is rarely produced in Britain. Division in spring just before growth starts. Very easy, it can be carried out successfully at any time in the growing season and can be planted directly into its permanent positions.

Known hazards of Acorus calamus

The fresh root can be poisonous. When using the plant medicinally, the isolated essential oil should not be used. The essential oil in the roots of some populations of this plant contains the compound asarone.

This has tranquilizing and antibiotic activity but is also potentially toxic and carcinogenic. It seems that these compounds are found in the triploid form of the species (found in Asia) whilst the diploid form (found in N. America and Siberia) is free of the compounds.

However, the root (but not the isolated essential oil) has been used in India for thousands of years without reports of cancer which suggests that using the whole herb is completely safe, though more research is needed.


*This article was originally published at www.naturalmedicinalherbs.net