Growing Irises

Of the large and varied family of irises cultivated today the bearded iris of the germanica type is the one most commonly grown. The original bearded iris, I.germanica, had purple flowers with a purple beard and ‘falls’ that hung down with rather a sad effect, but beautiful modem cultivars have come a long way since then and are available in a rainbow of colours. The poise and elegance of the bearded iris, its sword-like leaves that are excellent contrast for the soft foliage of other plants, and its wide range of colourings, make it a perfect gap-filler when tulips are over and border plants not yet at their best.

Colours Bearded Irises

These range from snowy white through cream to shell-pink and apricot, from butter yellow to flax blue, from deep sapphire to ruby red and purple. There are also browns, tans and near blacks as well as bicolours, and the plicatas have markings of another colour etched on a paler ground. The upstanding portion of the flower, known as the ‘standard’ and the drooping tongue-like petal, known as the ‘falls’ are often different again, so that every conceivable combination of colour exists somewhere in a named cultivar.


The plants vary in height, from dwarfs a few inches high, through the intermediate irises, 16-24 in., to 4 ft. tall kinds. Dwarf bearded irises, forms of I. pumila or of I. chamaeiris and of many beautiful hybrids, can be used with great effect on rock gardens, in pockets in paving, on dry walls or in sinks and troughs. Their flowers, on stalks a few inches high, resemble the tall flags. They flower during late March and April. They are vigorous and need re-vitalizing by division and replanting every year or two.

Intermediate Irises

These, the result of crossing the dwarfs and the tall kinds, increase quickly and are less susceptible to rhizome-rot than the tall irises. Named cultivars come in a wide variety of colours. Though tall flags are better planted apart from other perennials which prevent the sun from reaching and baking their rhizomes, the intermediate irises are happy at the front of the border. Flowering in May, they prolong the season. They are rarely more than 2 ft. tall.

Tall Bearded Irises

The tall bearded irises flower in late May and June. Though the blooms are individually short-lived, a succession of flower-buds ensures weeks of colour. The modern kinds branch out, the better to display their numerous flowers.


Bearded irises are the most good-natured of hardy plants, provided their modest requirements are met. These are:

  1. Proper preparation of the ground before planting.
  2. A sunny site.
  3. A well-drained soil containing lime, which should be deeply dug, and some humus-forming material incorporated before planting (on no account use animal manure).


Always plant shallowly but firmly, barely covering the rhizome so that the sun can bake it. Artificial fertilizers are not necessary if the soil is fertile; excess of nitrogen tends to lush leaf growth and loss of flower. Plants must be hand-weeded; since hoeing can damage the rhizomes. Flower-stems should be removed as close to the ground as possible, but sound leaves should not be shortened until they die down naturally.

The best time for planting or dividing is soon after the flowers are finished, when congested clumps should be split up and only the young vigorous fans, each with a rhizome and strong roots, replanted. Space the tall irises 2 ft. apart; the dwarfs and intermediate kinds should be planted more closely. The most effective way for all bearded irises is to plant in blocks of one colour; they look their loveliest grouped together, in island beds or standing alone, surrounded by stone paving, a perfect setting for their beautiful flowers.

Bulbous Irises Bulbous Irises

Dwarf bulbous iris provide some of the most striking splashes of colour in the winter garden. I. Danfordiae, canary-yellow, and I. histrio aintabensis, blue, flower during January and look well planted together. The brilliant blue I. histrioides ‘Major’, with flowers 4 in. across on short stems, flowers before the leaves appear. The bulbs of these tend to split up into tiny bulb-lets so that it is best to renew annually, potting on the little offsets until they reach flowering size. In February and March flower the sweetly scented, violet-purple I. reticulata and its cultivars, pale blue ‘Cantab’, reddish-purple ‘J. S. Dijt’ and dark blue ‘Royal Blue’.

The Spanish, Dutch and English irises make good clumps in the border. The Dutch, at 2 ft., flower in May and June. The colours are white, yellow, mauve and blue. They are followed by the Spanish irises, I. xiphium, in a similar colour range. Both are excellent cut flowers. Bulbs are so cheap that it is worth planting annually, though many will flower each year in a dry soil. The English irises, I. xiphioldes, flower in June and July.

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