Harlequin Blueflag (Iris versicolor)

Blue Flag 

Harlequin Blueflag, more commonly called Blue Flag, is an emergent plant found in wetlands, marshes and on the shores of ponds and lakes. The genus and species name is Iris versicolor and it is in the Iris Family (Iridaceae). The order is Asparageles, the same order under which asparagus is listed. However, Blue Flag has poisonous rhizomes and the sap can cause skin irritation similar to that of Poison Ivy. In spite of its attractiveness, Blue Flag should be left alone.

The flower is iris-shaped and from 2½ inches (6.3 centimeters) to 4 inches (10 centimeters) wide. The sepals are the largest part of the flower and have a blue and white pattern tinged at the base with yellow or greenish-yellow. The petals are shorter, doubly lobbed and blue to almost white. The photograph above of the Blue Flag flower was taken at French Hill Pond in May 2010. The photograph below shows entire plants photographed at the Wild Gardens of Acadia about the same time.

The leaves of the Blue Flag plant are linear, from 8 inches (20 centimeters) to 32 inches (80 centimeters) long and from ½ inch (1.3 centimeters) to 1 inch (2.5 centimeters) wide. The following photograph shows the leaves and seed capsules.


Blue Flag Leaves and Capsules


The fruit is a capsule about 1½ inches (3.8 centimeters) long with three blunt lobes or cells. These capsules drop into the water and float away to establish a new plant. The following photograph shows one of these capsules. When mature, the capsules are brown.

Blueflag Seed Capsule

The next photograph shows one of the three seed chambers in the capsule and part of another.

Blueflag Capsule Single Chamber

The photograph below shows the other two seed chambers. The seeds shown are immature and will turn brown when matured. Note the single seed on the ruler that has a length of about 5 millimeters (1/5 inch). There are about a dozen seeds per chamber.

Blueflag Capsule Double Chambers

The root system is a corm.

This plant flowers from May through August but is most showy in May and early June.

Blue Flag  

Animals and people have been poisoned by this plant. Practitioners of traditional medicine use small quantities of the dried rhizome as a cathartic and diuretic. The poison in the rhizome is iridin, a glycoside. Like other emergent plants, Blue Flag helps filter runoff water before it enters the pond.


1. Flora of North America, Iris versicolor, retrieved from http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200028227, 8/1/2026.

2. Lady Bird Johnson Wildflower Center, Iris versicolor (Harlequin blueflag), retrieved from http://www.wildflower.org/plants/result.php?id_plant=IRVE2, 8/1/2016.

3. Minnesota Wildflowers, Iris versicolor (Harlequin Blueflag), retrieved from https://www.minnesotawildflowers.info/flower/harlequin-blueflag, 8/1/2016.

4. Mittelhauser, Glen H., Linda L. Gregory, Sally C. Rooney and Jill E. Weber, The Plants of Acadia National Park, The University of Maine Press, Orono, Maine, 2010, p. 210.

5. Niering, William A., The Audubon Society Field Guide to North American Wildflowers (Eastern Region), Alfred A. Knopf, New York, 1988, p.565.

6. United States Department of Agriculture, Forest Service, Iris versicolor, retrieved from http://www.fs.fed.us/wildflowers/beauty/iris/Blue_Flag/iris_versicolor.shtml, 8/1/2016.

7. United States Department of Agriculture, Plants Database, Iris versicolor, retrieved from http://www.plants.usda.gov/core/profile?symbol=IRVE2, 8/1/2016.

8. Wikipedia.org, Iris versicolor, retrieved from https://en.wikipedia.org/w/index.php?title=Iris_versicolor&oldid=724181072, 8/1/2016.


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