Iris ensata Japanese Pinwheel - Japanese Water Iris

Iris ensata 'Japanese Pinwheel' is a particularly elegant variety of Japanese water iris, with large violet-purple flowers edged in white, illuminated by a superb golden yellow spot. This beautiful variety also has the ability to re-flower during the season, if the conditions are right. Unlike our garden irises, this rhizomatous perennial is comfortable in non-limestone and waterlogged soils in summer. Stunning when planted in mass in wet areas and on the banks of water points, Iris ensata were once intensely cultivated in Japan, especially around Edo (the ancestor of Tokyo), for cut flowers.

Iris ensata (synonym kaempferi), hanashōbu in Japanese,  better known as Japanese water iris, bear no resemblance to our classic garden irises, except for belonging to the Iridaceae family. The original Iris ensata is a fibrous rhizome plant native to Asia, specifically wet areas in Japan, the Himalayas, and Siberia. These irises, known to be difficult to cultivate, love acidic and peaty soils (cannot tolerate excess limestone), are water-hungry during their growth and flowering period, but appreciate slightly less moist soils in winter: in nature, they are found above the water level, which often decreases in winter and rises again in spring with the melting snow.

The cultivar 'Japanese Pinwheel' is a horticultural creation by Currier McEwen dating back to 1988. This excellent variety has been recognized in dedicated competitions (Honorable Mention in 1990 – Payne Award in 1992). The plant forms an erect tuft, reaching about 1m (3ft) in height when in bloom and 50cm (20in) in width. This iris slowly spreads on the ground through its rhizomes, beautifying year after year. The foliage, deciduous in winter, is medium green and composed of long, slender ribbon-like leaves, sheathing at the base and marked by a prominent central vein. The flowering, more or less perpetual, takes place between May and August-September depending on the climate. Floral stems emerge from the leaf tufts. Each stem bears 2 to 3 large flowers measuring 12cm (5in) in diameter. Each flower is composed of 3 large, flat, and horizontal sepals, topped by 3 much smaller and finer petals. Sepals and petals are violet-purple with a hint of magenta and finely edged in white.

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