northern blue flag

(Iris versicolor)

Conservation Status
northern blue flag
  IUCN Red List

not listed


N4N5 - Apparently Secure to Secure

SNR - Unranked


not listed

Wetland Indicator Status
  Great Plains

OBL - Obligate wetland


OBL - Obligate wetland

  Northcentral & Northeast

OBL - Obligate wetland


Northern blue flag is a 24 to 36 tall, erect, perennial forb that rises on a single stem from a thick, creeping, freely-branching rhizome and fleshy roots. It often forms large clumps.

The stems are erect, stout, nearly straight, and usually have 1 or 2 branches. The top of the stem is equal to or higher than the leaves.

Basal leaves are narrowly sword-shaped, green to grayish-green, 4 to 32 long, and to 13 16 wide. They are erect and commonly arching near the top. There are 1 or 2 leaves on the stem subtending each branch. Stem leaves are similar to the basal leaves but shorter.

The inflorescence is a cluster of 2 to 4 flowers at the end of each stem and branch. The cluster emerges from an enveloping pair of large bracts (spathes).

The flowers are 2½ to 3½ wide. There are 3 petals and 3 petal-like sepals, all of which are fused at the base into a to ½ long tube. Each sepal is egg-shaped to kidney-shaped, widely spreading, 1½ to 2¾ long, and ¾ to 1½ wide. It is abruptly or gradually narrowed toward the base (clawed) and broadly expanded toward the tip. It is violet blue near the tip and white with heavy purple veins from the middle to the base. There is a greenish-yellow patch near the throat. What appears to be an upper lip is actually a branch of the style. The highly modified style is enlarged and divided into 3 branches. Each petal-like style branch covers the lower portion of a one sepal, extending just beyond the narrowed claw and concealing the stamens. The style branch is 13 16 to 1 long, distinctly ridged, and flared at the tip. It does not have ear-like lobes at the base. The 3 petals are much smaller than the sepals. They are lance-shaped, erect, ¾ to 2 long, and 3 16 to ¾ wide. They are rarely notched at the tip. The flowers last 1 to 4 days and are somewhat fragrant. All white flowers are found, though rarely.

The fruit is a green, oblong, three-sided, 1½ to 2 long, ½ to ¾ in diameter capsule. It is rounded-triangular in cross section.




24 to 36


Flower Color


Violet blue


Similar Species


Southern blue flag (Iris virginica var. shrevei) stem leaves often exceed the inflorescence. The sepals and petals are lighter in color, lavender to violet. The patch at the base of the sepals is bright yellow, not yellowish-green. The 3 petals are often notched at the tip.


Wet. Meadows, swamps, marshes, streambanks. In water less than 40 deep. Full to partial sun.




June to July


Pests and Diseases






Distribution Map



2, 3, 4, 5, 7, 28, 29, 30.









  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Liliopsida (monocots)  


Asparagales (agaves, orchids, irises, and allies)  


Iridaceae (irises and allies)  
  Subfamily Iridoideae  
  Tribe Irideae  


Iris (irises)  
  Subgenus Limniris  
  Section Limniris  
  Series Laevigatae  



Iris versicolor var. versicolor


Common Names


blue flag iris

harlequin blueflag

northern blue flag

northern iris













Modified leaf at the base of a flower stalk, flower cluster, or inflorescence.



A stalk-like narrowed base of some petals and sepals.



Long, straight, and narrow, with more or less parallel sides, like a blade of grass.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.



An outer floral leaf, usually green but sometimes colored, at the base of a flower.



One or two large bracts that subtend, hood, or sometimes envelope a flower or flower cluster, as with a Jack-in-the-Pulpit.

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    northern blue flag      


    northern blue flag      


    northern blue flag   northern blue flag  


    northern blue flag   northern blue flag  


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  Iris versicolor
Zi W
  Iris versicolor  
  Blue Flag (Iris versicolor)
Andree Reno Sanborn
  Blue Flag (Iris versicolor)  



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Other Videos
  Blue Flags in the Bluebelt

Uploaded on Jun 4, 2008

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, fleur-de-lis, flower-de-luce.

The bluebelt is man-made and abounds with local native plantings and each rock is laid in by hand.

  Minnesota Native Plant - Northern Blue Flag (Iris Versicolor)

Published on Jun 13, 2014

Rich shows off the Northern Blue Flag (Iris Versicolor) around the pond. A great plant for a Minnesota native wetland or water garden!






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