Iris – Perennial Plant, How to grow

Iris - Perennial Plant, How to grow

From the Greek iris, a rainbow (Iridaceae). A large genus of bulbous, creeping and tuberous rooted perennials, some of which are evergreen. They are natives of the north temperate zone from Portugal to Japan. Among the most varied and beautiful of flowers, irises have been compared to orchids by some gardeners who, without the required greenhouse facilities for orchids, have decided to specialize in this most interesting genus. They may be divided into six main sections : tall bearded, dwarf bearded, beardless, Japanese, cushion or regelia and bulbous-rooted.

Tall bearded These are known best as the flag or German irises, flowering in May and June, and suitable for growing in ordinary, well-drained borders, especially on chalk. I. flavescens, 21 feet, pale lemon flowers, almost white, probably of garden origin. I. florentina, 2i feet, white flowers tinged pale blue on the falls, May; grown near Florence for orris root. This iris is the fleur-de-lis of French heraldry. I. germanica, common iris, 2-3 feet, lilac-purple flowers, May. Other forms slightly differently coloured.

Dwarf bearded Growing requirements similar to those of the previous section. I. chamaeiris (syn. I. lutescens), 10 inches, blue, purple, yellow or white, tinged and veined brown, April-May, S. Europe. Most variable in colour and growth, and frequently confused with I. pumila. I. pseudopumila, 6-9 inches, purple, yellow or white, April, southern Italy. I. pumila, 4-5 inches, almost stemless and much variation in colour, April, Europe, Asia Minor.

Beardless Species suitable for moist soils, margins of pools or streams: I. douglasiana, 6-12 inches, very variable in colour, violet, reddish-purple, buff, yellow white, May, leaves evergreen and leathery, California. I. fulva (syn. I. cuprea), 2-3 feet, bright reddish-brown, June-July, southern United States; var. violacea is a violet form. I. foetidissima, gladwyn iris, 2 feet, lilac-blue flowers followed by an ornamental seed capsule with breaks to expose brilliant orange seeds in winter, Britain. I. ochroleuca, 4-5 feet, creamy-white, with orange blotch, June-July, western Asia Minor. I. pseudacorus, yellow flag or water flag, 2-3 feet, bright orange-yellow, May-June, Europe including Britain; variegata, with variegated leaves. I. sibirica, 2-3 feet, blue, purple, grey or occasionally white, June-July, invaluable for waterside or border planting, central Europe and Russia. I. versicolor, 2 feet, claret-purple, May-June, N. America.

Species requiring sunny borders : I. chrysographes, 1feet, deep violet with golden veins, for a moist place, June, Yunnan. I. innominata, 4-6 inches, golden-buff, veined light brown, and there are lavender, apricot and orange-yellow forms, Oregon; ‘Golden River’ is an attractive named variety. I. japonica (syn. I. fimbriata),   feet,
lilac, spbtted yellow and white, evergreen, sage-green leaves, April, Japan, China. The form ‘Ledger’s Variety is said to be hardier than the type. I. tectorum, 1-1J2 feet, bright lilac, flecked and mottled with deeper shades. There is a white form. Lift and divide after second year’s flowering, May-June, Japan. I. unguicularis (syn. I. stylosa), 1 foot, lavender, blue, November-March, ideal in dry poor soil against south wall. One of the gems of winter. Japanese: These species thrive in 2-4 inches of water and do well in moist soil or on the margins of ponds.

I. kaempferi, clematis iris, 2 feet, varying shades lilac, pink, blue and white, June and July. I. laevigata, 2 feet, deep blue, June and July.

Cushion or Regelia Very beautiful, easily grown hardy irises, doing best in a calcareous soil in a sunny sheltered site.

I. hoogiana, 14-2 feet, soft lavender-blue flowers, early May, Turkestan. I. korolkowii, 1-14 feet, chocolate-brown markings on creamy-white ground, May, Turkestan.

Bulbousrooted Other than the Spanish and English iris which may be planted on sunny borders, this section includes choice kinds which may be grown in pots in the alpine house or in the rock garden. I. bucharica, 1-14 feet, golden-yellow falls and small white standards, April, Bokhara. I. bakeriana, 4-6 inches, deep violet, with a touch of yellow on the falls, January-February, Asia Minor.


I. danfordiae, short, bright yellow, January and February. A gem but rarely survives to flower a second year.

I. filifolia, 1-14 feet, deep purple, June, southern Spain. I. graeberiana, 6-8 inches, mauve falls marked cobalt-blue and whitish veins. For a sunny position, April, Turkestan. I. histrioides, short, dark blue, purple, January, Asia Minor.

I. reticulata, 6 inches, violet, purple and yellow, February, Caucasus. I. winogradowii, 3-4 inches, light yellow, January-February, Caucasus. I. xiphioides, English iris, 1-2 feet, various colours, June-July, Pyrenees. I. xiphium, Spanish iris, 1-2 feet, various colours, white, yellow or blue, with orange patch on blade, May-June, south Europe and North Africa.

Miscellaneous I. cristata, 4-6 inches, pale lilac with deep yellow crest. A delightful miniature for a sink garden in full sun, May-June, eastern United States. I. vicaria (syn. I. magnifica), 2 feet, white, tinged pale blue, April, central Asia. Other species are offered by specialist nurseries.

Cultivation The most widely grown of this large and varied family are the tall bearded irises. These colourful hybrids

have been developed by plant breeders from the long-cultivated, dark blue Iris germanica. This type of iris is one of the few plants that may be lifted, divided and replanted soon after it has finished flowering, preferably in July. By planting in July the fleshy rhizomes will soon make new roots in the warm soil and will be firmly established before the winter.

Choose a sunny well-drained site, and if planting in wet, heavy soil is unavoidable, build the bed up a few inches above the surrounding level. On light soil, add leafmould or peat, but manure should be used sparingly, for it will only induce soft growth. These irises like lime, so if the soil is deficient in this, work in some builder’s rubble. Bonemeal and bonfire ash are both useful for feeding irises. It is important not to bury the rhizome when planting. In nature, it grows along the surface of the soil, and if the rhizome is planted too deep a year’s flowering may be lost. On light soil it is necessary to plant somewhat deeper, otherwise the plants are liable to topple over. It is usual at planting time to cut back the sword-like leaves, but. this can be overdone, for the plants do depend, to some extent, on the leaves to assist them in making new roots; drastic cutting back should be avoided. When planting, leave ample room between each variety so that the rhizomes will not require lifting and dividing for three years.

those who do not know one variety from another the best way to start a collection is to buy 12 varieties in 12 different shades of colour from a specialist iris nursery. With some 300 different named varieties listed in iris cataloges it will be an easy matter to obtain individual varieties to increase the selection. Among outstanding modern hybrids are: ‘Berkeley Gold’, a handsome tall deep gold; ‘Blue Shimmer’, ivory-white dotted with clear blue; `Caprilla’, yellow-bronze falls and blue-lavender standards; ‘Chivalry’, a ruffled medium blue; ‘Cliffs of Dover’, creamy-white; ‘Dancer’s Vale’, with pale violet dottings on a white ground; ‘Desert 1 Song’, a ruffled cream and primrose; `Enchanter’s Violet’, violet; ‘Golden Alps’, white and yellow; ‘Green Spot’ ; `Harriet Thoreau’, a large orchid-pink self; ‘Inca Chief’, a ruffled bronze-gold; `Jane Phillips’, intense pale blue; `Kangchenjunga’, pure white ; ‘New Snow’, pure white with bright yellow beard; Pegasus’, a tall white: ‘Party Dress’, a ruffled flamingo-pink ; ‘Patterdale’, a clear pale blue; ‘Regal Gold’, glowing yellow; ‘South Pacific’, a pale shimmering blue: ‘Total Eclipse’, almost Mack with a similar coloured beard, anu. many Benton hybrids raised in Suffolk by Sir Cedric Morris. Another amateur iris breeder in this country, the late Mr H. J. Randall, made crosses of many of the best American hybrids with remarkable success.

Waterside irises are charming beside a formal pool or in a wild garden. The June-flowering I. sibirica and its hybrids have long been appreciated. They thrive in boggy conditions, although they will grow in a border provided the soil is deeply dug, reasonably moist and in partial shade. In the bog garden they flower happily in full sun. Good hybrids include; ‘Heavenly Blue’, ‘Perry’s Blue’ with china-blue flowers on 3-foot stems, and ‘Eric the Red’ with heavily veined wine-red flowers. The elegant I. kaempferi, of Japanese origin, is in all its glory in July. The flowers are large and handsome, with blends of colour of great charm. There are both single and double varieties in shades of velvety purple, rosy-lilac, plum and white shaded blue, for instance, ‘Morning Mist’, purple, flecked grey, and a double white, ‘Moonlight Waves’. They must have lime-free soil and, for that matter, lime-free water. They like a rich loam with ample moisture during the growing season but moderately dry roots during the rest of the year. Another handsome Japanese species, I. laevigata, is sometimes confused with the clematis-flowered I. kaempferi. The large, brilliant, violet-blue flowers of I. laevigata are borne on 2-foot stems at intervals from June to September, above a mass of deep green, arching foliage. It does well in a bog garden or in water up to 4 inches deep. The North American, claret-coloured water-flag, I. versicolor, is also a good waterside plant.

These waterside irises are best propagated by division of the roots in the spring, although it can be done in the
autumn if necessary. They may also be raised from seed sown in a cold frame in the autumn in well-drained soil, covering them with 4 an inch of sifted soil. They should germinate in the spring, but some may prove erratic, so do not discard the pans in too much of a hurry.

The bulbous irises are quite distinct from the tall bearded and waterside irises. They are admirable for the rock garden or in a sunny well-drained border containing plenty of sharp sand or grit. Plant the bulbs in September. The miniature varieties which flower in February and March may also be grown in pans in a cold greenhouse or frame—the violet-blue I. reticulata, and its pale blue variety ‘Cantab’, I. histrioides major, bright blue with yellow markings, and bright yellow I. danfordiae, are particularly suitable for this purpose. The taller growing Dutch, Spanish and English irises are easily grown in any reasonably good soil in the garden and are most useful for cutting. Plant the bulbs in October about 4 inches deed in a sunny position. The Dutch irises produced by crossing I. xiphium with other bulbous species, flower in June, followed a little later by the Spanish and then the English. The English irises prefer a cool moist position and should be left undisturbed for three or four years before being lifted and divided. Dutch and Spanish irises should be lifted every year after the foliage has died down and stored until planting time. There is a good selection of named varieties to be found in bulb cataloges.

By making a careful selection of the many different types of iris, including the April-flowering Juno species and hybrids which have brittle swollen roots needing careful handling, it is possible to have irises of one sort or another in flower for many months of the year.

How to grow Iris

Iris (eye-ris)

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