The Friends of the Wild Flower Garden, Inc.

Plants of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States


Common Name
Blue Flag Iris (Larger Blue Flag, Harlequin Blue Flag, Northern Blue Flag)


Scientific Name
Iris versicolor L.


Plant Family
Iris (Iridaceae)

Garden Location


Prime Season
Early Summer Flowering



Blue Flag is a plant of marshes and wet meadows, growing 1 to 3 feet high on solid stems.

Leaves are sword shaped, 20 to 40 inches long, green to grayish-green color and prominently veined, with a raised (thickened) mid-rid in mature leaves. As basal leaves, they rise from the root in a fan shape, erect, and then later drooping. The flower stem may also have a few leaves and these are usually short and do not rise above the flower stalk.

The inflorescence consists of 2 to 4 flowers, that are similar to many beardless iris, at the top of a solid stem that rises from the root. Stems may branch once and may have some stem leaves. The upper section of the stem under each flower forms a spathe covering the ovary of the flower. Bloom time is the end of May to the end of June in this part of Minnesota depending on the season's weather.

Flowers are blue to purple (are rarely white), about 4 inches wide. The three outer ovate violet-blue sepals spread outward; the base narrows abruptly with a hairy greenish or yellowish patch surrounded by white, lined with purple veins - this area being known as a 'signal'. The Garden plants have a yellow spot. Very showy. The petals (often called 'standards' in the Iris genus) are the same color but are oblong, much shorter that the sepals, have smooth margins and are upright. The fruiting parts are in the center of the flower. The styles form flat arms, with curled tips and smooth margins, which reflex outward and lie atop the base of the sepals with the anthers and stigma hidden from view between the two protecting the pollen from rain. The nectar of the plant is in glands at the base of the petals.

Fruit: The seed forms in a somewhat 3-sided cylindrical capsule, each side has 2 rows of seeds which are thin, D-shaped, and hard (not corky like I. pseudacorus). These capsules often overwinter. Seeds are distributed by wind when the capsule opens. These seeds require at least 120 days of cold stratification for germination and are thus best propagated by sowing outside in the fall.


Habitat: The root stock is a branching rhizome with fleshy roots. Branches are the same size and texture as the main rhizome (said to be 'homogeneous'). Propagation is by seed or single rhizomes cut from the main root stock. The plant will spread vegetatively to form large clumps if left undisturbed. While the plant has few pests or diseases, it can be overgrown by more aggressive plants. However, in wet grazing meadows it may be weedy as grazing animals will not eat it but do eat its competitors. I. versicolor requires a wet meadow or marshy area with full sun to grow best.

Names: The genus name, Iris, is after the Greek goddess of the rainbow. The species, versicolor, means 'variously colored'. The author name for the plant classification, 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparison: The other iris in the Garden wetland is Yellow Flag Iris, Iris pseudacorus L. This is a non-native iris considered to be an invasive species, but has been allowed to exist in the Garden under control. Of closer resemblance is I. virginica, the Southern Blue Flag where the only visual difference is that the signal area is a pubescent yellow only without the yellow patch being surrounded by the purple-on-white veined area.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Blue Flag Blue flag

Above and below: Iris flower parts are 3 sepals (spreading) called 'falls' and 3 smaller petals between them (upright) called 'standards'. Lying on top of the sepals are the styles with an upturned tip (the style crest) (2nd photo below). Under the style crest is the stamen (below 1st photo) and the lip of the stigma. The bulge in the stem just below the sepals (above 2nd photo) is the ovary, covered by a green spathe.

anthers style crests

Below: 1st photo - The three-sided seed capsule of Blue Flag. Each side has two rows of half-moon (D-shaped), hard seeds. 2nd photo - The prominently veined strap-like basal leaves.

Blue Flag seed capsule leaf
Blue Flag
Clump of Blue Flag


Notes: Blue Flag is indigenous to the Garden area. Eloise Butler catalogued it on May 25, 1907 and she planted it in 1925. Ken Avery planted it in 1965 and Gardener Cary George planted some in 1987. It is native to most of Minnesota except counties in the SE and most of the Western counties. In the SE quadrant of the state there is another species, Iris virginica, that replaces the Iris versicolor. On a map of North America the plants' range would be the NE quadrant, not south of West Virginia and north to Hudson Bay. It is a beautiful flower of the moist woodland. The plant needs moist soil and in the Garden it occurs along the wetland trail (Lady Slipper Lane).

There are three species of wild Iris found in Minnesota. The introduced I. pseudacorus, Yellow Flag and two native species - I. versicolor, Blue Flag (or Northern Blue Flag), and I. virginica, Southern Blue Flag.

Eloise Butler has this to say about the Iris: “If eyes were made for seeing, we do not need to be poets in order to note the grace of the recurved petals, the stately pose of the flower and the choice reserve that withholds, except under close inspection, the delicate finish of etched lines and blending of color. The flower is richer than other lilies by reason of the pistil terminating above in three leafy divisions colored like the petals. Behind them are artfully concealed the three long stamens in exactly the right position for the insect guest to be powdered with the pollen." Published in the Minneapolis Sunday Tribune July 2, 1911. Read entire article [NOTE: Eloise refers to "recurved petals", but those are actually the sepals of the flower, the petals being the upright standards.]

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

graphicIdentification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.