This interesting member of the crested iris group is beardless, but the falls are marked by a fringed crest of white on purple. Japanese roof iris are an example of the great diversity of exotic Iris species coming into the nursery industry with varied colors and flower formations. Though the bloom is large at 6 inches, the standards are shortened and tubular and the falls widespread. The leaves are 15 inches tall, fanned at the base and ribbed. The rhizomes should be spaced 10-16 inches apart planted at 1-2 inches deep and will mature at soil level. They prefer a sunny to part-shade location in rich, well-drained soil and benefit from the shelter of a wall with western or southern exposure and winter mulch. Japanese roof iris is also useful in wet areas, such as around ponds and fountains. But they do not require a great deal of water so they can be used in rock gardens. As the rhizomes spread, this iris can be used for naturalizing and mass planting. The common name is derived from the historical use on thatched roofs in its native China and Japan. These iris tolerate drought and deer. Insects, Diseases, and Other Plant Problmes: Prone to slugs and viruses. Infected plants with darkened leaves should be removed and destroyed. The seeds do not harbor the infection. 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.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
High Organic Matter
Soil pH
Acid (<6.0)
Soil drainage
Good Drainage
Available space
12 inches-3 feet
NC region
Coastal; Mountains; Piedmont
Mature size
Height: 1 ft. 0 in. - 1 ft. 6 in. | Width: 1 ft. 0 in. - 1 ft. 6 in.
Growth rate
Medium
Maintenance
Low
Canopy layer
4 - Herbaceous (1-3 ft)
Form & Appearance
Habit / form
Clumping; Erect
Leaf color
Green
Leaf shape
Lanceolate
Leaf margin
Entire
Leaf feel
Smooth
Hairs present
No
Leaf detail
Knife-like, narrow, ribbed to 15" long, spreading at base
Flower color
Blue; Pink; Purple/Lavender; Variegated; White
Flower value
Good Cut; Showy
Flower shape
Irregular
Flower size
> 6 inches
Flower detail
6" flowers with 3 short, tubular, upright standards, 3 spreading, pendant falls, and white crests
Bloom time
Spring
Fruit type
Capsule
Fruit detail
capsule
Wildlife & Ecology
Native status
Non-native
Origin
China
Play value
Attractive Flowers
Food & Medicine
Fruit type
Capsule
Landscape Use
Landscape location
Pond; Riparian
Landscape theme
Water Garden
Design feature
Mass Planting
Garden tags
#poisonous #purple #lavender #groundcover #naturalizes #rhizomes #shelter for wildlife #showy flowers #white flowers #drought tolerant #riparian #deer resistant #wet soils tolerant #summer flowers #problem for dogs #problem for cats #problem for horses #full sun tolerant #partial shade tolerant #cutting garden #perennial #contact dermatitis
Problems & Resistance
Insect problems
Slugs and Snails Found on Flowers and Foliage
Problems
Frequent Disease Problems; Poisonous to Humans; Problem for Cats; Problem for Dogs; Problem for Horses
Resistant to
Deer; Drought
Particularly resistant to
Deer
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.
Toxic principle
Pentacylic terpenoids (zeorin, missourin and missouriensin), Irisin, iridin, or irisine