The Iris and its Cultivation

The iris is a plant of two distinct groups, those producing their flowers from a bulb and those which grow from perennial rhizomes, and which are generally found in the herbaceous border. The flower which grows from the rhizome is popularly called the Flag or German iris, whilst the iris used for early summer cut flower in such vast quantities is called the Dutch iris and grows from a bulb. There is also a Spanish iris which flowers in early June immediately after the Dutch section – and an English iris which follows in July. Thus by using a cold greenhouse or cloches, it is possible to enjoy these lovely bulbous plants from mid-April to the end of July. They are one of the easiest of all flowers to grow and must be the least expensive.

There is also a wide range of delightful species of dwarf iris which are superb for the rockery and for indoor pot culture, several of which will come into bloom early January, whilst others will extend the flowering season right through spring. There are also a number of the German section which are of dainty dwarf habit and ideal for the rockery. All irises, with the exception of the moisture-loving species, have one thing in common, they enjoy, dry, sunny conditions and they like a limey soil. They are mostly natives of south-east Asia and of southern Europe, particularly the Pyrenees region, hence their liking for dry conditions.


As more Dutch iris are grown commercially than any other of the species on account of their early-flowering habit, this section is perhaps the most important. Planting should be carried out from October 1st until mid-November, though October planting will ensure the formation of roots and therefore anchorage against hard frost.

My own method of planting is first to prepare a bed 3 ft. wide which will enable picking of the blooms to be done easily. As irises like dry conditions, especially during winter, a raised bed will suit them best. This should be made up in September, incorporating some sand and leaf mould. If the soil is light in texture, some well-rotted manure, either of horses, cows or pigs will give it the necessary ‘body’, for although the iris enjoys dry conditions, some humus is essential to the formation of a tall, well-formed spike. A raised bed will ensure that the bulbs are in no way waterlogged should a long, wet period be experienced in the early part of the winter and before the bulbs have formed their roots.

If the ground lacks lime, rake in some lime rubble or a small quantity of hydrated lime, but the bed must be given three weeks in which to settle down, for bulbous irises are like onions and shallots in their demanding of a firm planting bed. To make quite sure that the bed is compact, it is as well to tread it all over a day or so before the bulbs are planted. Some writers on the subject suggest planting in drills made 3 in. deep and placing the bulbs 1 in. apart. My own method, which is most successful, is to plant exactly as for shallots, just pressing the bulbs into the soil so that their noses may be seen at ground-level. They are planted 2 in. apart in rows the same distance apart so that they will hold up each other when coming into bloom and will require no staking other than placing a cane at the four corners of the bed and tying around a thick piece of twine. So as to ensure a firm bed, I run the garden roller over as soon as planting has taken place, and of course provided the soil is in no way sticky in which case planting will wait until it becomes friable.

The blooms will be ready for picking early in May, six months after planting the bulbs, and they must be removed before the flower heads are fully opened. Several days may be saved, and every day means a more profitable crop, if the blooms are removed as soon as showing colour and allowed to stand in buckets of cold water for twenty-four hours before dispatching to market or shop. The flower stems, being of a high water content, will continue to supply the blooms with moisture and they will continue to open all the time. A bloom which is too open will bruise and rapidly deteriorate.

If a good-sized bulb is planted, one 7-8 cm. As against the 6-7 cm. size, and the beds are watered with liquid manure every fortnight, it will be possible to grow the same bulbs for a second season. In order to help the bulbs as much as possible it is advisable to leave a piece of stem and leaf rather than to cut the bloom at ground-level. Bulbous iris grown in the border for decoration should have the flower heads removed after flowering and the stem and foliage should be allowed to die down as for all other bulbs.

Bulbous iris used in the border should be planted in clumps of six bulbs. As when planted in beds for cutting I prefer to plant in separate colours and in alternate varieties. But do not neglect to plant the Spanish and English types which will prolong the flowering season into July, and whilst the Spanish and English iris may not have much commercial value, they are invaluable for early summer cutting. They require much the same treatment as described for Dutch iris, though the English iris enjoys a heavier and slightly moister soil.

All these irises should, where possible, be planted in a position sheltered from the prevailing winds on account of their tall habit. A wall or hurdle screen is ideal – the shelter of trees is not suitable for the plants must have full sun.


All bulbous irises enjoy a dry, deeply worked soil and a sun-baked position. They will not grow well in a starved soil – it should be well drained and be enriched with some humus, but a soil retaining too much water, especially during summer may cause rotting of the bulbs. And they love lime. In dry, chalky soils which are difficult for so many plants, these lovely irises should be planted in large numbers to give bloom from November until June.

If grown in pots and under completely cool conditions the bulbs may be dried off and kept in the pots under the greenhouse bench throughout summer and repotted again in September and placed in the plunge bed.

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