Iris ensata Rose Queen - Japanese Water Iris

Iris ensata 'Rose Queen' is a variety of Japanese iris that charms with its large flowers in two shades of pink animated by a bright yellow signal at the base of each petal. Plant this rhizomatous perennial in moist soil, for example on the banks of a pond or in good loamy soil, never drying out in summer, but not waterlogged in winter. It can be grown in full sun or light shade, in acidic to neutral soil. Superb planted en masse near water features, Iris ensata also offer beautiful flowers for bouquets.  

Iris ensata (synonym kaempferi), hanashōbu in Japanese, more commonly known as Japanese water iris, bears no resemblance to our classic garden irises, except for their membership in the iris family. The original Iris ensata is a fibrous rhizomatous plant native to Asia, specifically to the wet areas of Japan, the Himalayas, and Siberia. These irises, known for being difficult to cultivate, thrive in acidic and peaty soils (intolerant of limestone), require plenty of water during their growth and flowering period, but appreciate slightly drier soils in winter: they are found in nature growing above the water level, which often drops in winter and rises again in spring with the melting snow. 

The 'Rose Queen' water iris forms an erect, rather upright clump, reaching a height of 80cm (32in) when flowering (60cm (24in) for the foliage) and measuring 40 to 50cm (16 to 20in) in spread. The plant slowly spreads across the ground through its rhizomes, becoming more beautiful year after year. The deciduous foliage is medium green and composed of long, slender, ribbon-like leaves, sheathing at the base and marked by prominent central veins. Flowering takes place between June and August depending on the climate, in the middle of the Japanese water iris season, lasting for 3 good weeks. Flower stalks emerge from the leaf clumps. Each one bears 2 to 3 large flowers measuring 12-15cm (5-6in) in diameter. They are composed of 3 large pendulous sepals, pale mauve-pink washed with a brighter pink around a small bright yellow signal, topped with 3 small petals of the same light lavender pink. The centre of the flower is occupied by 3 small upright petaloid styles, also pink mauve in colour. 

Often cultivated on the banks of ponds and basins, Iris ensata, like many marsh plants, can tolerate having 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 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 capillary action. Associate 'Rose Queen' Iris ensata with Anemone rivularis, Daylilies, Darmera peltata, Lobelia 'Queen Victoria', Astilbes, Physostegia virginiana, Lysimachias, and Ligularias. 

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