Larger blue flag iris, is a perennial in the Iridaceae (iris) family native to Canada and the United States spanning south from Nova Scotia into the middle and northeastern United States to Virginia. The specific epithet, versicolor , is derived from this plant's ability to produce many-colored blooms while the common name, "flag", comes from an old English word (flagge) for reeds and refers to its natural preference to wetlands. It prefers to grow in rich, moist soils and thrives in full sun while it tolerates partial shade. Plants can be grown in up to 4 inches of standing fresh water. The sword shaped blue-green clumping leaves reach 2 to 2.5 feet tall topped with a mass of blue lavender to white blooms. The blooms are formed of three upright inner standards and three distinctly marked sepals or falls. The leaves are narrow and strap-like 1 inch wide and up to 24 inches long crossing at the base to be fan-like. Though the fruit forms as a capsule, this plant propagates best by division of the rhizomes after blooms fade. Prune back the leaves after the first frost to just above the crown. Grow in containers in ponds or other water gardens in up to 4 inches of standing water. It is most happy in wet areas of pond margins, wet meadows, and marshy areas where it multiplies naturally forming clumps. It tolerates browsing by deer. Insects, Diseases, and Other Plant Problems: Aphids, iris borer, iris thrips. Disease problems include blossom or leaf blight, baterial soft rot, crown rot, rhizome rot, leaf spot, and mosaic virus. More information on Iris .
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Height: 2 ft. 0 in. - 3 ft. 0 in. | Width: 2 ft. 0 in. - 2 ft. 6 in.
Maintenance
Low
Canopy layer
4 - Herbaceous (3-15 ft)
Form & Appearance
Habit / form
Arching; Erect
Foliage
Deciduous
Leaf color
Blue; Green
Leaf shape
Lanceolate
Leaf margin
Entire
Leaf size
> 6 inches long, < 1 inch wide
Hairs present
No
Leaf detail
Blue green sword-like leaves 2 feet long and 1 inch wide, entire margins, they stand upright or arch slightly.
Flower color
Blue; Purple/Lavender
Flower value
Good Cut; Showy
Flower size
3-6 inches
Flower detail
1-several at the top of a naked stem, 6-parted with 3 outer, spreading or pendent "falls" and 3 inner, erect "standards", variously colored The large 4-inch flowers bloom in late spring to early summer with several (3-5) on a naked stalk of up to 30 inches.
Fruit type
Capsule
Wildlife & Ecology
Native status
Native
Origin
Central & Eastern Canada to North Central & Eastern U.S.A
Play value
Colorful
Food & Medicine
Fruit type
Capsule
Landscape Use
Landscape location
Meadow; Pond; Riparian; Small Space
Landscape theme
Cutting Garden; Water Garden
Design feature
Border; Mass Planting
Garden tags
#swamps #pond margins #blue flowers #purple flowers #water garden #marshes #large flowers #flowers early summer #problem for dogs #problem for cats #problem for horses #full sun tolerant #partial shade tolerant #wet soils tolerant #cutting garden #border planting #flood tolerant #standing water tolerant #low maintenance #deer resistant #boggy sites #collier preserve tn #wildflower #HS304 #blue leaves #pond #wetland #contact dermatitis
Problems & Resistance
Insect problems
Aphids on Ornamental Landscape Plants; Slugs and Snails Found on Flowers and Foliage
Problems
Problem for Cats; Problem for Dogs; Problem for Horses
Resistant to
Deer; Wet Soil
Propagation
Division
Poison severity
Low
Poison parts
Roots; Sap/Juice; Seeds
Poison symptoms
CAUSES ONLY LOW TOXICITY IF EATEN. SKIN IRRITATION MINOR, OR LASTING ONLY FOR A FEW MINUTES. Nausea, salivation, vomiting, abdominal pain, lethargy, diarrhea, elevated temperature following ingestion; skin irritation upon contact with seeds, rootstock, or cell sap. Highest concentration in rhizomes.
Toxic principle
Pentacylic terpenoids (zeorin, missourin and missouriensin), Irisin, iridin, or irisine