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Iris Versicolor: Blue Flag Iris


The Blue Flag Iris is a perennial plant with sword shaped leaves that range from 60 to 90 cm tall with large blue-violet flowers. The plant grows from a fleshy and fibrous rhizome in swampy and moist environments across the United States and Canada. The leaves tend to grow from the base of an erect stem and are at least 1 cm wide and fold at a midrib. The flowers are interesting in that the petals and sepals are of two forms and are planar. Large seeds are produced from a 3-celled fruit that develops from an inferior and bluntly-angled ovary. The plant is primarily pollinated by insects and can also self-fertilize. I. versicolor will grow best in zone 5 in sandy to loamy soils and flowers from May to June. The plant is versatile when it comes to soil pH with the ability to grow in acidic, neutral, or basic soils. Though requiring moist to wet soils such as bogs or marshes, the plant grows successfully in partly-shaded to full sun areas. Finally, Blue Flag may be propagated via seed or bulb. Seed should be planted in a cold frame as soon as they are ripe. When seedlings are large enough to be transferred, they should be placed into individual pots and grown in a greenhouse or cold frame for the entirety of their first year. Plantlets may be placed in their plots in late spring or early summer. Divisions should be done after flowering with larger clumps ready for direct planting. Smaller divisions should be allowed to grow as the seedlings for the first year,as previously mentioned.


The active chemical in Blue Flag is a nauseous and bitter glucoside known as iridin, was first isolated by Tiemann and De Laire.  The glycone portion of the molecule is D-glucose and the aglycone portion is called iridigenin, found in smaller concentrations than the complete molecule. Not surprisingly, the pigment present in the flowers may be extracted and used as an acid-base indicator. There are no reports in literature of a mechanism of action, though its mechanism of action and metabolism are probably very similar to that of the alkaloids.

Fun Fact:





A member of the “mint family”, it is most commonly served as a tea to improve general digestion, ease flatulence, relieve colic, alleviate menstrual cramping, and reduce nausea and vomiting. Today, it is also used largely as decoration for its aesthetic properties.

Contraindications/Interactions/Adverse Reactions

Due to the high toxicity of the rhizome, it is NOT recommended that this medicinal herb be used medicinally in ones home.


  1. Strange, Richard Le. History of Herbal Plants. New York: Arco Pub. Co., 1977.
  5. Tiemann, F.; De Laire, G.; J. Am. Chem. Soc. 1893, 15, 351.

Researched By: Josh Judkins