Iris versicolor

Blue Flag

Iris versicolor, Blue Flag, Little Beartrack Lake, BWCAW, Photo courtesy Richard W. Swanson
Blue Flag
Little Beartrack Lake, BWCAW
Photo courtesy Richard W. Swanson

Flora, fauna, earth, and sky...
The natural history of the northwoods


  • Iris, the Latin for Iris
  • versicolor, from the Latin, "with various colors"
  • Blue Flag, from its flower color and the old word for Iris
  • Other common names include: American Blue Flag, Dagger Flower, Dragon Flower, Flag Lily, Harlequin Blueflag, Liver Lily, Poison Flag, Snake Lily, Water Flag , Water Iris, fleur-de-lis, flower-de-luce, clajeux (Qué), Lis met Bontkleurige Bloem (NL), kosatec strakatý (Slovak)


  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Liliopsida, the Monocotyledons
      • Subclass Liliidae
        • Order Liliales
          • Family Iridacae, the Irises
            • Genus Iris, the Irises
  • Taxonomic Serial Number: 43196


  • A hardy lakeshore perennial herb of shallow water, 2'-3' tall
  • Leaves narrow, sword-shaped bears two ranks of sword-shaped, long, narrow leaves sword-like leaves emerge from thick horizontal root stock (corm) which are covered with fibrous roots. This emergent will grow to heights of four feet in spreading clumps. The individual leaves are somewhat shorter than the entire plant. Leaves are folded on the midribs so that they form an overlapping flat fan.
  • Stems unwinged, erect, generally have basal leaves that are more than 1 cm. wide. stout stem grows from a thick, cylindrical, creeping rootstock nearly straight flowering stems
  • Rhizome tends to form large clumps from thick, creeping rhizomes.annual joints, 2" or more long, about ¾" in diameter, cylindrical in the lower half, becoming compressed towards the crown, where the cup-shaped stem-scar is seen, when dry, and numerous rings, formed of leaf scars are apparent above and scars of rootlets below. It is dark brown externally and longitudinally wrinkled. The fracture is short, purplish, the vascular bundles scattered through the central column.
  • Root rootlets are long, slender and simple.
  • Flower large, showy, light to deep blue with yellow and whitish markings at the base of the sepals. Borne 2-3 to a stem. The well developed flower petals and sepals spread out nearly flat and have two forms.
    • Sepals 3, petal-like, spreading or recurved with a greenish-yellow blotch at their base.
    • Petals 3, smaller than the sepals
    • Stamens
    • Pistils
    • Ovary inferior (below flower), bluntly angled.
  • Fruit a three celled, bluntly angled capsule, 1½" long and ¾" in diameter. Two rows of densely packed seeds form within each cell.
  • Seed large, brown, with a flattened round form. Can be observed floating on the water's surface in the fall. Average of 18,000 seeds per pound.


  • A waterside and shallow water plant; the only iris native to the North Country.
  • Distinguished from the closely related, more southerly species, Iris virginica, by its cauline (stem) leaves that often exceed the flowers whereas the cauline leaves of Iris versicolor are usually shorter than or equal to the height of the flowers.


  • Newfoundland to Manitoba, south to Florida and Arkansas.
  • Iris versicolor tends to be more northern in its regional distribution, while Iris virginica is more southern.
  • Abundant in swamps and low grounds throughout eastern and central North America, common in Canada, as well as in the United States, liking a loamy or peaty soil.


  • Edges of ponds and moist soils; shallow waters, sedge meadows, marshes, and along streambanks and shores
  • Marshes, swamps, wet meadows, along shorelines, and in forested wetlands.


  • Trees: Tammarack (Larix laricina), Black Spruce (Picea mariana)
  • Shrubs: Bog Birch (Betula pumila), Leatherleaf (Chamaedaphne calyculata), Sweet Gale (Myrica gale)
  • Herbs: Cattails (Typha spp)
  • Ground Covers: Sphagnum Mosses (Sphagnum spp.)
  • Mammals: Moose (Alces alces), rootstock fed upon by aquatic rodents.
  • Although the seed is large and kernel-like, there is no documentation of wildlife consumption


  • Native Americans used the root for dropsy and as a cathartic and emetic.
  • Leaves have been used externally for burns and sores.


  • Used as a garden ornamental for its brightly colored floral display.
  • Root mass of established colonies provides good shoreline protection.
  • Rhizome long used in herbal medicine
    • traditionally gathered in the fall
    • contains starch, gum, tannin, volatile oil, 25% acrid, resinous matter, isophthalic acid, traces of salicylic acid, and possibly an alkaloid as well as a number of still unidentified substances. Owes its alleged medicinal value to an oleoresin.
    • powdered extracts are known as Iridin or Irisin
    • said to act upon the liver and bowels; claimed useful for syphilis, dropsy, low-grade scrofula and skin afflictions, and as a diuretic.


  • Reproduces by seed and vegetatively by rhizomes
  • Flowers May to July.


  • By seed
    • seed will naturally shatter from their dry pods in fall
    • stratify in moist peat moss for at least three months at 0-36º F.
    • plant for spring germination
    • fall seeding can be considered, but is typically less successful.
  • By rhizome division
    • single corms or bulbs can be divided or cut from the parent root system, then potted or directly planted.
    • best done before the end of July to allow plants to become established


  • Hardy to USDA Zone 2 (average minimum annual temperature -50ºF)
  • Cultural Requirements
    • Sun full
    • Soil heavy, rich, organic; pH 5-7
    • Constantly moist or wet, up to 6" deep
    • Fertilization minimal if any
  • Will tolerate moderately brackish water, partial shade, and permanent inundation
  • Will grow less than 2' per year radially
  • Good for water gardens and bogs. One of the easiest, and showiest, of native aquatics for the home gardener.
  • Species available by mail order from specialty suppliers or at local nurseries
  • No known insects or diseases, but muskrats are fond of chewing on the root.
  • Is easily over-topped by aggressive rhizomotous emergents.



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Last updated on 26 February, 2004