Native Americans chewed the root or made a tea from the dried root for treating gas, stomachaches, indigestion, heartburn, fevers, colds, and coughs; anti-spasmodic, anti-conversant, central nervous system depressant; in India it has been used for many years as an aphrodisiac. They also chewed the root to stave off thirst and as a stimulant on long journeys.
German studies showed the controlled dosages of the root helped lower serum cholesterol levels in rabbits.
In Appalachia, freshly cut leaves are still used as an insecticide.
The inner portions of the tender young shoots make a very tasty Spring salad. The Pennsylvania Dutch used the root to flavor pickles and the powdered root has been used to make cachets and scent perfumes.
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 flavouring. Rich in starch, the root contains about 1% of an essential oil that is used as a food flavouring. The root also contains a bitter glycoside. Some caution is advised, see the notes on toxicity.
The dried and powdered rhizome has a spicy flavour and is used as a substitute for ginger, cinnamon and nutmeg.
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 flavour custards in the same way as vanilla pods.
The inner portion of young stems is eaten raw. It makes a very palatable salad.
Sweet flag has a very long history of medicinal use in many herbal traditions. It 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 on toxicity for more information.
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 chewing the root alleviates toothache. It is a folk remedy for arthritis, cancer, convulsions, diarrhoea, dyspepsia, epilepsy etc. Chewing the root is said to kill the taste for 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 gall bladder.
Warning! – Some species are thought to contain the carcinogen beta-asarone. Vapors from the roots do repel some insects. The root, when candied, was a long-time pioneer confection. It was boiled all day long, cut into small pieces, and then boiled again for a few more minutes in thick maple syrup. This “candy” was used most often used to aid digestion, but also used to serve as a tonic and physic.