southern blue flag

(Iris virginica var. shrevei)

Conservation Status
southern blue flag
  IUCN Red List

not listed


N5 - Secure

SNR - Unranked


not listed

Wetland Indicator Status
  Great Plains

OBL - Obligate wetland


OBL - Obligate wetland

  Northcentral & Northeast

OBL - Obligate wetland


Southern blue flag is a 20 to 40 tall, erect, perennial forb that rises on a single stem from a thick, creeping, freely-branching rhizome and fleshy roots. It often forms dense clumps.

The stems are erect to arching and usually have 2 or 3 branches. They seldom fall over after flowering. They are shorter than the leaves so that the leaves rise above the flowers.

Basal leaves are narrowly sword-shaped, green to grayish-green, 23½ to 31½ long, and 1 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 2 or 3 flowers at the end of the stem and 1 or 2 flowers at the end of the branch. The cluster emerges from an enveloping pair of large bracts (spathes).

The flowers are 3 to 3½ wide. There are 3 petals and 3 petal-like sepals, all of which are fused at the base into a to ¾ long tube. Each sepal is egg-shaped to oval, widely spreading, arched, 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 pale blue to purple near the tip quickly fading to white with darker blue or purple veins toward the middle. There is a bright yellow patch near the throat. The claw is green in the center, surrounded by bright yellow, with purple veins. 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 smaller than the sepals. They are lance-shaped to spatula-shaped, erect, 1¼ to 2¾ long, and to 1¼ wide. They are often 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, elliptical to egg-shaped, three-sided, 1¼ to 2 long, to ¾ in diameter capsule. It is rounded-triangular in cross section.




20 to 40


Flower Color


Lavender to violet


Similar Species


Northern blue flag (Iris versicolor) top of the stem is equal to or higher than the leaves. The sepals and petals are darker in color, violet blue. The patch at the base of the sepals is yellowish-green, not bright yellow. The 3 petals are not notched at the tip.


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




May to July


Pests and Diseases






Distribution Map



2, 3, 4, 5, 7, 24, 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  
  Species southern blue flag (Iris virginica)  



Iris shrevei

Iris versicolor var. blandescens

Iris versicolor var. shrevei


Common Names


Shreve’s iris

southern blue flag

southern blueflag

Virginia blue flag













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.

Visitor Photos

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Kirk Nelson

    southern blue flag   southern blue flag  

Southern blue flag iris, on the shore of Pickerel Lake

    southern blue flag   southern blue flag  

Found on the shore of Pickerel Lake

    southern blue flag   southern blue flag  


    southern blue flag      


    southern blue flag      


    southern blue flag   southern blue flag  
    southern blue flag   southern blue flag  



  Virginia Blueflag (Iris virginica)
Bill Keim
  Virginia Blueflag (Iris virginica)  



Visitor Videos

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Other Videos
  blue flag (Iris virginica)

Uploaded on May 19, 2010

Aquatic and Invasive Plant Identification Series by the UF/IFAS Center for Aquatic and Invasive Plants ( ) and the Florida Fish and Wildlife Commission, Invasive Plant Management Section.

For more information about blue flag, go to

Video editor/videographer - Phil Chiocchio

  Southern Blue Flag Iris

Published on Jun 28, 2012

Wild Iris (Iris virginica) in wetland restoration near Ridgetown, Ontario




Visitor Sightings

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  Kirk Nelson

Location: Mississippi National River and Recreation Area - Coldwater Spring

southern blue flag  
  Kirk Nelson

Location: Lilydale Regional Park

Southern blue flag iris, on the shore of Pickerel Lake

southern blue flag  
  Kirk Nelson

Location: Lilydale Regional Park

Found on the shore of Pickerel Lake

southern blue flag  




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