Iris ensata is also known as the Japanese Iris, Japanese Flag, Sword-leaved Iris, Japanese Water Iris, or in Japanese Hanashōbu 花菖蒲 and it was formerly called Iris kaempferi. The name ensata means sword referring to its leaves.
It is part of the Iridaceae family of plants and it is native to Japan, China, Korea, and Russia, its native habitat is usually boggy or marshes with low acid soil. It is a rhizomatous, herbaceous perennial. It is hardy to -4ºF or -20º C. Though Iris ensata has been cultivated for five centuries it was only introduced to the western culture in the 19th century.
Iris ensata can grow to about 90cm or 3ft tall. The foliage is sword-shaped and medium green. It blooms in the summer, bluish-purple flowers appear on tall stems, either one or two flowers to each stem. It is a beardless Iris but it has a yellow stripe on the falls or bottom petals.
It is easy to grow. Plant Iris ensata in the sun or partial shade, in humus-rich, moisture-retentive, acid soil. It can actually do well in 6in or 15cm deep water during its growing season but not in the winter or dormant season. But they will also do well in borders and just moist soil as well. Iris ensata thrives on fertilizers.
Iris ensata is usually disease-free and pest-free, but watch out for slugs and snails. Propagate Iris ensata by division in autumn. Plant rhizomes about 2in or 5cm deep. Like other irises, they are poisonous and should not be consumed.