IRIS

The tall bearded or flag irises are among the easiest of all herbaceous perennials to grow well. They give excellent results in town gardens, being extra hardy and markedly drought-resistant. A sunny, well-drained position is essential. Both heavy and light soils are suitable, although on very heavy soil it may be necessary to raise the bed a few inches and give a dressing of basic slag to improve the texture.

Hop manure, compost and similar humus-forming materials may be worked in before planting but avoid fresh manure of any kind as it may cause rotting of the rhizomes. Lime need only be added on really acid land.

Plant in late June directly after the plants have finished flowering, from early August to mid-October or in late February and early March — irises planted at this time must not be expected to bloom freely during the first season. Plant firmly, barely covering the rhizomes with soil as they appreciate a thorough sun-baking. Each rhizome should be about 10 in. apart. Lift established plants every third or fourth year after flowering and replant the outer rhizomes in each clump singly. Do not cut off foliage after flowering as the plants grow and breathe through the leaves. Brown, withered leaves should only be detached when absolutely dead.

Iris Diseases.

Leaf spot. A fungus disease which is sometimes troublesome on wet soils, especially after flowering and where weeds have not been controlled. The brown spots have a yellowish margin and eventually turn grey. Burn all infected leaves and spray with Bordeaux mixture. Soft rot or rhizome rot. More prevalent in warm, wet weather. It causes the rhizomes to become soft and pulpy. Bad drainage encourages this disease. Cut off the infected portion of the rhizome and sprinkle the cut surface with copper-lime dust. A top-dressing of superphosphate of lime is also helpful.

Choice of varieties. The varieties of tall bearded iris described later can be confidently recommended to beginners. The majority are fairly new introductions, many of American origin. The colours will be a revelation to those who only know the old-fashioned blues and purples and are unaware of the various pinks, reds and browns which are now available. The terms fall and standard refer to the three lower, semi-drooping petals (falls) and the three upper petals (standards).

Irises occupy a fair amount of space and as they must have plenty of sunshine and will not thrive if crowded among other plants in a herbaceous border, amateurs often ask about interplanting for succession etc. Various suggestions are given below. The varieties described later are in bloom from early May to about mid-June. Note that the common purple flag iris is often in flower in April in an early season. Thus those varieties listed as early will usually bloom during the first half of May, the mid-season varieties (which comprise the majority) later in the month, followed in early June by the really late kinds such as Lady Mohr, Staten Island and Wabash.

To secure a succession of bloom interplant with antirrhinums, pent-stemons or petunias. On cool soils, gladioli are possible but remember that these tall irises dislike wet ground and gladioli will not give best results on very dry land. Among low-growing shrubs, Perovskia atriplici-folia, Potentilla fruticosa Vilmoriana and lavender are alternative choices.

Yellow and orange:

Benton Regan: sometimes described as honey-orange but amber may be nearer. Lasts well and is useful for the front of the border growing to only 2 ft. Very late. Berkeley Gold: orange-yellow. Late.

Golden Fleece: lemon-yellow with creamy falls edged gold. Mid-season. Golden Hind: deep buttercup-yellow. A fine variety unfortunately sometimes liable to soft or rhizome rot. Mid-season. Mabel Chadburn: medium yellow with extra large blooms. Late. Naranja: yellow suffused deep orange. Mid-season. Rocket: standards deep chrome, falls orange-chrome. Mid-season. St. Crispin: lemon-yellow with orange-yellow beard. Mid-season.

Red:

Display: glowing red. Very free flowering. Late.

Ethel Peckham: crimson-red. Sometimes blooms again in autumn. Very fragrant. Mid-season.

Master Charles: velvety mulberry-purple blooms, very freely produced.

Mid-season.

Red Gleam: comes near to scarlet. Late.

Red Orchid: claret-red. Fragrant. Short grower to about 1 ft. Early Senlac: an old variety with mulberry-red fragrant blooms, very freely produced. Late.

Late Mahogany: deep mahogany-red. Mid-season.

Pink:

All mid-season varieties.

Che’rie: flamingo-pink with ruffled flowers and tangerine beard. Craithie: sea-shell pink. Very free-flowering.

Loomis V. 20: another sea-shell pink, but with an apricot tinge. Fragrant. Mary Randall: deep rose-pink with a tangerine-red beard, almost a raspberry pink.

Spindrift: coral-pink with a deep tangerine beard. Flowers of fine texture which are unaffected by strong sunlight.

Strathmore: apricot-pink again with a tangerine-red beard. Good branching habit. Tea Rose: coppery-pink.

Blue and Purple, including Near Black:

Aline: powder-blue. Fragrant. Early.

Arabi Pasha: cornflower-blue, with no veining. Mid-season. Black Hills: bluish-black. Tall grower. Mid-season. Great Gable: dark blue-purple. Mid-season. Harmony: purple-blue. Early. Honor Sterndale: amethyst-violet. Fragrant. Late. Maisie Lowe: dark velvety-blue. Mid-season.

St. Osyth: Cambridge blue. Short grower to about 2 ½ ft. and useful for the front of the border. Mid-season.

Sylvia Murray: pale silvery-blue. Extra large flowers on firm, well-branched stem. Tall grower to about 4 ft. Fragrant. Mid-season.

White and Cream:

Some of the whites show slight traces of cream, blue or mauve on first opening. Ideally, they should be grown on their own as they seem to show up better, otherwise try to place alongside pale blue kinds like Aline, St. Osyth and Sylvia Murray. On no account mix with yellow or orange varieties.

Arctic Snow: pure glistening white. Very fragrant. Mid-season.

Clijfs of Dover: ruffled milk-white. Tall. Mid-season.

Dame Caroline: another tall white with branching habit, and flaring waved falls. Early.

Gudrun: an old variety still worth growing. Large white, falls faintly tinged yellow. Yellow beard. Short grower. Fragrant. Midseason.

Mew Snow: Pure snow-white with bright yellow beard. Ruffled flowers.

Mid-season.

White City: very large blooms with flushes of plumbago-blue when young.

Smooth and of fine texture. Strong, branching stems on a tall plant to about 4 ft. Increases quickly. Fragrant. Mid-season.

Other Colours:

Argus Pheasant: soft brown. Late. Cleo: chartreuse-green. Fragrant. Mid-season. Cordovan: rich coppery-brown. Late.

Fort Ticonderoga: orange-brown with vivid orange beard. Mid-season. Juliet: coppery-salmon and yellow. Mid-season.

Lady Mohr: Exotic is perhaps the best adjective to describe this remarkable colour blend which comprises oyster-white and pink, greenish-yellow and reddish-violet. Tall grower. Late. Pinnacle: clear white standards and pale yellow falls. Mid-season. Staten Island: golden-yellow standards and rich red falls. Tall grower. Late.

Tarn Hows: Reddish cedar-wood brown. Mid-season. Wabash: white standards and violet falls, margined white. An unusual ‘ colour contrast. Tall grower. Late.

Other Types of Iris:

Iris unguicularis (stylosa), also known as the Algerian iris, is a plant for every garden, given a few essentials which are not difficult to provide. Plant at the base of a south or south-west wall (a greenhouse wall at the back is ideal, especially if heated, but is certainly not essential). Poor, limy soil is necessary. Work in coarse mortar rubble and rough sandstone. The fragrant lavender-blue flowers are borne at intervals from December to March and may be cut in the bud stage to open indoors.

There is a white form and a deep violet variety, Iris unguicularis speciosa, which does not bloom until March. September planting is best as the plant must not be allowed to dry out until it has established root-hold. Some experts advise April planting but one may then have to water to counteract drought. Once this iris is established it will tolerate prolonged drought. It may take 18 months to settle down, no flowers being produced during this period. Keep a sharp watch for snails and slugs and use a metaldehyde preparation as necessary to keep them at bay. Increase by lifting in September and replanting portions with at least three shoots. Other winter-flowering irises include the bulbous, fragrant Iris reticulata which grows to 9 in. The violet-purple flowers have a golden-yellow blotch, appearing in February. Plant 3 in. deep in October. Cantab is a delightful Cambridge blue, slower to increase and therefore more expensive, J. S. Dijt, reddish-purple and very free-flowering, Royal Blue which is best described as Oxford blue, and Wentworth, a purple-blue. All are excellent for growing in pots. Iris histrioides maior bears larger flowers than any of the reticulata group, is rather shorter in growth, blooms several weeks earlier and is a rich blue. All the foregoing may be increased by division in September.

The Dutch, English and Spanish irises are also bulbous. They bloom in June and early July, growing to about 2 ft., are useful for cutting and may be planted about 3 in. deep in September. Lift in August as soon as they show signs of overcrowding, dry off and replant in October. A cool soil suits all these irises, especially the English varieties which prefer a moist loam. Among the Dutch varieties the golden-yellow Princess Beatrix and the pure white and yellow Princess Irene are outstanding. Iris japonica Ledger’s variety, though often said to require a cool root run, will succeed under the same conditions as Iris unguicularis. The fringed lilac and yellow flowers are of surpassing beauty and very freely produced. It is easily increased by division in late summer or early autumn.

Iris kaempferi (the Japanese iris) grows to about 3 ft. It is moisture-loving and quite useless planted in dry ground. Lime-free soil is essential. Work in plenty of compost peat and well-rotted manure. The immense flowers, up to 9 in. across, are mauve, violet, grey, blue, crimson etc. Increase by division in spring.

Iris sibirica also appreciates a cool position, but is happy in a sunny border. Most varieties reach 3—4 ft. Good varieties include the violet-purple Caesar, the wine-red Eric the Red, Gatineau, a vivid sky-blue, and Wisley White. Increase by division in spring.

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