The blue flag has several common names such as poison flag, flag lily, liver lily, snake lily, dragon flower, harlequin blue flag, larger blue flag, and northern blue flag.


The blue flag is native to North America, the Eastern United States, and Eastern Canada. It is found in marshes, swamps, wet meadows, ditches, and shorelines.


The blue flag is a flowering herbaceous perennial plant, grows up to 80 cm high. It forms large clumps from thick, creeping rhizomes. The unwinged, erect stems generally have basal leaves.

Part used

The medicinal part is derived from the rhizome of the plant.

Traditional Uses and Benefits

  • Native Indians from North America have used to treat skin-related conditions like sores, burns, rheumatism, syphilis, acne, eczema, and bruises.
  • Externally, it was used in swellings, bruises, burns, ulcers, inflammation, and blood poisoning. Internally, it was used to treat colds, sore throats, lung troubles, and a drastic purgative/cathartic.
  • In 1749 the Colonials were using the drug to treat leg sores and other slow-healing wounds.
  • Even minimal amounts of blue flag can bring instant relief from vomiting and nausea. However, an overdose of this plan can cause side effects like vomiting.
  • Blue flag is known as Liver Lily since the dried roots of the herb help solve liver problems. Some chemicals present in the plant helps in bile production and stimulating the liver’s functions.
  • In modern herbalism, it is used to detoxify the body – it increases urination and bile production and has a mild laxative effect.
  • It also solves the following health problems: fluid retention, bloating, chronic rheumatism, weight gain, colic, and pelvic inflammatory ailments.

Dosage and Precautions

There is no specific dosage for the blue flag. According to expert opinion, the fresh rhizome can be used externally for the treatment of skin diseases. It should not be taken by mouth. It may irritate the mouth and may cause nausea and diarrhea.

The blue flag can be used in different forms; decoctions, dried rhizomes, fluid extracts, powdered roots, solid extracts, and tinctures.

Warning: There are several poisoning cases of humans and animals. Glycoside and iridin compounds in rhizomes may cause poisoning. The sap can cause dermatitis in susceptible individuals.  Pregnant and breastfeeding women should not use this plant.



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