Tips for growing that eye-catcing iris

Bulbous irises make valuable additions to the garden by providing a continuity of attractive flowers. The reticulatas often bloom in late winter and last into mid-spring. They overlap the blooming period of junos, which flower in midspring. The vivid flowers and unique flower form of the reticulatas seldom fail to attract attention.

Dutch, Spanish, and English irises provide colour in early and mid summer. This makes them useful at a time when most other bulbs have faded and annuals have only begun to reach their peak.Flowering periods vary with climates. In West Coast gardens, for instance, bulbous irises may bloom earlier than indicated here.

With only minor variations, as noted below, all bulbous irises like a well-drained soil and a spot in full sun where they can soak up plenty of summer heat.

• Good drainage is a key factor in growing junos.
• They generally require raised beds containing nearly neutral (pH 6.5 to 7.0) soil with a high clay content.
• Plant them singly or in clumps in early fall at a depth of five centimetres (two inches).
• Allow 15 to 22 centimetres (six to eight inches) between the bulbs.
• Handle them carefully to avoid breaking off the long, brittle storage roots, from which the essential feeding roots develop during the growing season.
• Bulbs of the reticulata iris should be planted in early to mid fall.
• Set them eight centimetres (three inches) deep and eight centimetres (three inches) apart in raised beds. Their soil should contain plenty of sharp sand, as poor drainage can be fatal.
• Dutch and Spanish irises can be treated alike.
• Plant them in midfall at a depth of 10 centimetres (four inches) where winters are cold; in milder climates plant at about six centimetres (two and a half inches).

Do not expect too much from these bulbs. Even under the most favourable circumstances, they may have to be replaced every two years.

English irises usually have a longer life than their Dutch and Spanish relatives. They need a mildly acid soil and semi-shade. Plant them 15 centimetres (six inches) deep in early fall.

During the growing season, watch the iris beds closely for signs of attack by pests and disease. Serious trouble is often easy to stop if it is identified in time.

• Remove any flowers that have faded. After the blooming season has ended for each variety, dust the beds with a low-nitrogen organic fertilizer, and scratch it into the soil.
• Give the planting bed a watering at this time, if rainfall is inadequate, but do not water during the summer months.
• Add to the mulch as needed. If weeds penetrate it, pull them out and place on the compost pile.
• Allow foliage to ripen undisturbed. Do not remove it until after it has turned brown, or the bulbs will not perform well the following year.
• To help screen the ripening foliage, you can sow annual seeds in the bulb beds. Do not do this where bulbs must be divided after their leaves have withered, however.
• When division is necessary, Dutch and Spanish irises should be dug up after their foliage has died.
• Leave them in a shaded, airy spot to dry out for three weeks.

They can then be separated, stored in a dry place, and replanted in mid-fall. Since the foliage of Dutch and Spanish irises develops in the fall, their bulbs must be mulched for protection in cold regions.