Iris ensata is a group of moisture loving rhizomatous perennials. There are now many hybrids which are much showier than the basic Iris ensata types. They normally come under the 'beardless' Iris category.

Iris ensata 'Sansation'.
The Iris ensata normally send up single stems from the rhizome - but sometimes branched stems. Each stem can bear 3 or even 4 individual flowers and as can be seen by the image, there are many choice - if not gaudy - varieties or cultivars.
Flowering period is normally mid summer - the image above was taken 23rd June. As distinct from the 'Bearded irises' this group like to have their rhizomes below ground level. As such, they respond well to mulching in the spring with a rich organic compost.
The plants grow to 90cm tall, and are clump forming.
They can be planted at the edges of ponds or any damp moist soil situation.