Common Name: Japanese iris
Type: Herbaceous perennial
Family: Iridaceae
Native Range: Temperate and tropical Asia
Zone: 7 to 9
Height: 0.75 to 1.00 feet
Spread: 1.00 to 1.50 feet
Bloom Time: May to June
Bloom Description: Pale blue to white with yellow crests
Sun: Part shade
Water: Medium
Maintenance: Medium
Suggested Use: Naturalize
Flower: Showy
Tolerate: Deer
Culture
Winter hardy to USDA Zones 7-9 where it is best grown in medium moisture, well-drained soils in part shade. Tolerates close to full shade. Plants perform well in Mediterranean-like climates, but often struggle in the St. Louis area (USDA Zone 6A and 5B) where they should be sited in protected locations. Spreads by long slender, creeping rhizomes, but is not invasive.
Noteworthy Characteristics
Iris japonica is a woodland iris that is native to forest margins and wet grasslands in Japan and China. It is a rhizomatous plant that typically grows to 10-12" tall. Thin, semi-glossy, sword-shaped basal leaves (12-20" long) grow in fans with downward arching tips. As rhizomes spread outward, new fans appear. Orchid-like flowers (to 2" diameter) bloom in spring. Falls are pale blue to white with prominent yellow crests and serrated edges.
Genus named for the Greek goddess of the rainbow.
Specific epithet means of Japan.
Problems
No serious insect or disease problems. Wet conditions in winter may cause root rots.
Uses
Excellent ground cover in areas where it is winter hardy.