Alphabetical Plant Listing

Iris ensata (Japanese Iris)

Japanese Iris, Japanese Flag, Japanese Water Iris, Sword-Leaved Iris, Iris kaempferi (Iris Ensata)


Native to Japan, Japanese Irises (Iris ensata) are among the most elegant and breathtaking Irises. More refined and less conspicuous than the Tall Bearded Irises, these Beardless Irises enjoy huge orchid-like flowers that are a delight to gaze at. Usually ruffled and flat in form, they rise on erect, sturdy stems atop a dense clump of sword-shaped, linear green leaves, up to 24 in. long (60 cm), with prominent midribs. They have been cultivated in Japan for over 500 years and are referred to as Hanashobu in Japan.

  • Blooming from early to mid summer, Japanese Irises are the last Irises to bloom, usually about 2 weeks after the Siberian Irises and about 3 weeks after the Tall Bearded Irises. There are early, mid or late season varieties, the late blooming ones starting blooming with the early blooming daylilies.
  • Japanese Irises tend to be tall, up to 3-4 ft. high (90-120 cm), with large and incredibly attractive flowers, which may reach up to 10 in. across (30 cm). Their exquisite flowers are broader and more flattened than those of other common Irises. They may be single, double or peony flowered and come in an array of gorgeous colors including blue, lavender, violet-red, pink and white.
  • Japanese Irises usually enjoy one branch with 2 buds in the terminal and 2 in the branch. However, many varieties can be raised to produce 2 branches and even more. 
  • Easy to grow, Japanese Irises perform best in full sun or part shade, in humus-richmedium to wet, acidic soils. They love moisture-retentive soils and thrive in standing water, up to 6 in. deep (15 cm), during their growing season. Since Japanese Irises do not cope well with standing water and boggy soils in winter, you may want to grow yours in pots that are sunk in water during the growing season but which then are moved to dryer ground for fall and winter.
  • Japanese Irises will grow successfully in ordinary garden soils or perennial borders as long as they receive adequate moisture, especially during their growing season. 
  • Japanese Irises are heavy feeders. Provide a balanced fertilizer, such as 12-12-12, in spring and just before blooming. 
  • No serious insect or disease problems. Watch for slugs and snails as well as wet conditions in winter which may cause root rot. 
  • Japanese Irises are perfect candidates for water gardensJapanese gardens, along pools or streams. They are so spectacular that they create a very remarkable show by themselves, without being combined with other flowers. Plant them in groups, where they will look better than placed in a row.
  • Propagate by division of rhizomes from midsummer to early fall. Remove any dying foliage in fall. Old flower stems may be cut down after flowering. 
  • To be planted in fall or spring. Plant your rhizomes approximately 2 in. deep (5 cm). After planting, add a heavy mulch of 2 to 3 in. (5-7 cm) to help conserve moisture and reduce weeds. 
  • Ingestion may cause severe discomfort

Guide Information

Hardiness 4 - 9
Heat Zones 1 - 9
Climate Zones 4, 5, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 1A, 1B, 2A, 2B, 3A, 3B
Plant Type Perennials
Plant Family Iris Ensata - Japanese Irises
Exposure Full Sun, Partial Sun
Season of Interest Summer (Early,Mid)
Height 2' - 4' (60cm - 120cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 18" - 24" (45cm - 60cm)
Depth 2" (5cm)
Water Needs Average
Maintenance Low
Soil Type Clay, Loam, Sand
Soil pH Acid
Soil Drainage Poorly Drained
Characteristics Cut Flowers, Plant of Merit, Showy
Tolerance Deer, Salt, Wet Soil
Landscaping Ideas Beds and Borders, Ponds and Streams, Wall-Side Borders
Garden Styles City and Courtyard, Coastal Garden, Informal and Cottage, Japanese Garden

yyama3270 / 123RF Stock Photo

While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.

Guide Information

Hardiness 4 - 9
Heat Zones 1 - 9
Climate Zones 4, 5, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 1A, 1B, 2A, 2B, 3A, 3B
Plant Type Perennials
Plant Family Iris Ensata - Japanese Irises
Exposure Full Sun, Partial Sun
Season of Interest Summer (Early,Mid)
Height 2' - 4' (60cm - 120cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 18" - 24" (45cm - 60cm)
Depth 2" (5cm)
Water Needs Average
Maintenance Low
Soil Type Clay, Loam, Sand
Soil pH Acid
Soil Drainage Poorly Drained
Characteristics Cut Flowers, Plant of Merit, Showy
Tolerance Deer, Salt, Wet Soil
Landscaping Ideas Beds and Borders, Ponds and Streams, Wall-Side Borders
Garden Styles City and Courtyard, Coastal Garden, Informal and Cottage, Japanese Garden
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