Common Name: Japanese water iris
Type: Herbaceous perennial
Native Range: Japan, northern China, eastern Russia
Zone: 4 to 9
Height: 2.00 to 4.00 feet
Spread: 1.50 to 2.00 feet
Bloom Time: June to July
Bloom Description: Blue, lavender, violet-red, pink, white
Sun: Full sun to part shade
Water: Medium to wet
Suggested Use: Water Plant, Naturalize, Rain Garden
Tolerate: Deer, Wet Soil
Easily grown in average, medium to wet soils in full sun to part shade. Loves acidic, organically rich, saturated, moisture-retentive soils. During the growing season, it thrives in standing water (up to 6” deep). However in winter, it is intolerant of both standing water and boggy soils where rhizomes may rot. In order to meet these somewhat unusual seasonal cultural requirements, plants may be grown in pots that are sunk half way in water during the growing season but then removed to dryer ground for fall and winter. Japanese iris grows surprisingly well in garden soils, albeit less vigorously, as long as it receives consistent moisture. Plant rhizomes approximately 2” deep in fall or spring.
Japanese iris or Japanese water iris is a rhizomatous beardless perennial iris that grows in slowly expanding clumps to 2-4’ tall. Sword-shaped, linear green leaves (to 24” long) have prominent midribs. Flowers (typically 3-6” across) have a distinctively flattened appearance. Cultivars come in single, double and peony flowered forms in a wide range of colors including shades of blue, lavender, violet-red, pink and white. Blooms early to mid summer (later than both bearded and Siberian iris). Synonymous with I. kaempferi.
No serious insect or disease problems. Wet conditions in winter may cause root rots. Watch for thrips.
Moist borders. Water gardens. Japanese gardens. Margins of pools or streams.