Iris ensata Iedo Mishiski - Japanese Water Iris

Iris ensata 'Iedo Mishiski' is a prince of acidic and humid lands in summer: from a beautiful clump of grass-like foliage emerge floral stems adorned with large round and open flowers that lie flat, of a vivid blue-violet and velvety colour, traversed by very dark veins and animated by a superb elongated spot, of a bright yellow marginated with white, very visible at the base of each sepal. Antipodal to our garden Iris, this rhizomatous plant thrives on the banks of water points, but also in heavy soils that remain cool in summer.

Iris ensata (synonym kaempferi), known in Japanese as hanashōbu, more commonly referred to as Japanese water iris, have nothing in common with our classic garden irises, except for their belonging to the Iridaceae family. The original Iris ensata is a fibrous rhizome plant native to Asia, specifically from the wetlands of Japan, the Himalayas, and Siberia. These irises, known to be difficult to cultivate, love acidic and peaty soils (do not tolerate excess limestone), are thirsty for water during their period of growth and flowering, but appreciate slightly less humid soils in winter: they are found in nature growing above the water level, which often decreases in winter and rises again in spring with the melting of snow.

The cultivar 'Iedo Mishiski' forms an erect, rather upright clump, reaching a height of 90cm (35in) when in bloom with a spread of 50 to 60cm (20 to 24in). The plant slowly spreads on the ground through its rhizomes, beautifying year after year. The deciduous foliage, of medium green colour, is composed of long and slender ribbon-like leaves, sheathing at the base, marked by a prominent central vein. The flowering takes place between June and August depending on the climate, lasting for 3 weeks. Floral stems emerge from the clumps of leaves. Each stem carries 2 to 3 very large flowers with a diameter of 12-15cm (5-6in). They consist of 3 large rounded and flattened sepals, topped by 3 wide flattened petals. The centre of the flower is occupied by 3 small petaloid styles, mauve infused with white.

Often cultivated on the banks of ponds and basins, Iris ensata, like many marsh plants, can live with their "feet" in water during summer, but their rhizomes do not tolerate being submerged during winter, especially if it is freezing. In our gardens, these Iris ensata will thrive in a loamy soil enriched with compost, but not drying out in summer. For example, plant them in a heavy soil forming a slight depression, at the bottom of a slope, or on a bank where the soil becomes moist through capillarity. Associate Iris ensata 'Iedo Mishiski' with Anemone rivularis, Daylilies, Darmera peltata, Lobelia 'Queen Victoria', Astilbes, Physostegia virginiana, loosestrifes, and Ligularias.

Excellent cut flowers, especially in ikebana, Iris ensata were once extensively cultivated in Japan for this purpose, especially around Edo (the ancestor of Tokyo).