Family: Iridaceae

The Iris is aptly called the rainbow flower as it is found in all colours of the rainbow and many combinations of those colours. It has been known since antiquity, and has found a place in myths, legends, medicine and religion, as well as in heraldry and magic. Irises comprise a very large plant group of over 300 species with many hundreds of cultivars, all with very varied habits and preferred conditions. Some, such as the Dutch iris, grow from bulbs. Others, such as the tall bearded iris and Louisiana iris (both hybrids of several species), Japanese iris (I. ensata, Synonyms: I. kaempferi) and Siberian iris (I. sibirica), grow from rhizomes. Irises generally have stiff, sword-shaped leaves, 40-80 cm (16-32 in) high, while the flowers rise on straight stems above the foliage. Most flower in spring or early summer. Louisiana and Japanese irises, in particular, make lovely cut flowers with quite a long vase life. Growing requirements vary, with many needing excellent drainage, while others, such as the Siberian iris and Japanese iris, can tolerate permanently damp ground.

Types

Bearded irises are hybrids and come in an amazing range of single colours and hicolours. Their graceful, elegant flowers open one or two at a time on stems held well above the fans of stiff leaves. Planted en masse they can be a breathtaking sight. Even a small group of these irises are worth growing.

Two species of iris are grown for the production of orris, used in perfumery. They are I. germanica, especially its variety florentina, and I. pallida. I. germa­nica is the 'fleur-de-lis' (literally 'lily flower') known to French history. Louisiana irises are bred from irises native to Louisiana and Florida in the United States and have a rather flat form. Hybrids available today include an amazing range of colours of astonishing depth and richness. From pure white to the darkest purple, there is one to suit every gardener. These plants love moist soil and full sun. Japanese irises have been grown in Japan for centuries, although their exact origin is obscure. They are known for their beautiful, flat flowers, some having wavy or frilled margins. Many have flowers that are veined or netted in deep colours. The colour range covers all the shades of blue, red and purple, with new shades appearing all the time. These irises are lovely as cut flowers. Siberian irises multiply well given the right conditions, especially plenty of moisture. The foliage of this group is narrower than that of some of the others and the colour range is confined mainly to white and shades of blue and purple. Varieties are now available in pinks and reds.

Cultivation

All four types discussed below prefer to be grown in full sun, with some protection from strong wind. The soil should be well enriched with organic matter. For bearded irises, it may be necessary to lightly lime the soil. Bearded irises require well-drained soil, while the others prefer a soil with good moisture-retention and can he successfully grown in damp soil on the margins of ponds. Japanese irises are more exacting in their requirements and must have quite acid soil -they will not tolerate lime in any form. Bearded iris should be planted with the rhizomes about 20 cm (8 in) apart and only the roots buried. Divide existing clumps immediately after flowering in late spring to early summer, cutting the leaves off to a short fan. Japanese and Siberian irises are best planted in late winter or early spring, at about 15-20 cm (6-8 in) apart, with the crown of the plant at soil level. Lifting and dividing of these is best done in late autumn or winter. Louisiana irises can also be planted in late winter or spring. Apply complete plant food as new growth starts in spring. Japanese irises, in particular, need additional manure or compost in spring as well as fertilizer. All irises appreciate deep, regular watering during their growing and flowering period. Japanese, Siberian and Louisiana irises, especially, need plenty of water to keep the soil moist through-out the entire growing season from spring to tall. After flowering, cut off spent flower stems and remove any foliage that has died, especially at the end of the growing season. These irises are fairly free of problems but there are diseases that can affect them, such as fungal leaf spot, which can be treated with copper oxychloride, and rust. With the latter, remove affected leaves and spray if necessary with a suitable fungicide. The rhizomes can also rot but there is usually little that can be done beyond removal of the affected plants.

Climate

Zone 7 for most species.