Iris- Flag

Irises belong to an extremely varied and important genus of garden plants. Many people find it difficult to understand why they have such diverging demands as to their culture. Many species, for instance, are waterside plants, whereas other garden irises must be considered as rock plants. Bulbous-rooted irises may be regarded as a separate group.


None of them are pronounced shade-lovers; full sun or very light shade is always essential. Drought-lovers, such as the magnificent germanica hybrids, are planted in raised beds or in the rock garden. Water irises and waterside plants are, of course, placed round the garden pond; and bulbous rooted irises, unfortunately not very strong, may be given a spot in the bulb garden. Culture Bulbous-rooted irises are rather sensitive to frost, so after being planted in the autumn they need adequate protection. They flower from mid winter to mid summer, depending on the species, after which it is advisable to lift the bulbs and keep them dry for a few months. They are replanted in mid autumn. Buying new bulbs every year is safer. Rhizomatous-rooted species, requiring a sunny, dry situation, are Iris cristata, Iris germanica and Iris pumila. They are planted in late summer or early autumn. A well-drained situation is important. Irises for damp soil are generally very simple to cultivate, especially the yellow iris, which also grows wild in this country; it is almost a weed. Iris sibirica, which may be given a somewhat drier position, is also easy to grow. The magnificent Iris kaempferi and Iris laevigata are more difficult. These species are best grown in plastic containers with a diameter of 30 cm. In spring the pots are put in the garden pond, just below the surface of the water. After flowering the pots are raised a little by placing stones underneath. From late summer onwards the pots must be kept perfectly dry, so that the plants will turn entirely yellow in early autumn. After the first night frosts the foliage is cut down to 5 cm, after which the containers are buried 20 cm under the ground. In early spring they are lifted and once more placed in the water. The soil should be renewed once every three years.


Rich, chalky soil for the bulbous-rooted species; rhizomatous-rooted species have approximately the same requirements. In both cases good drainage is essential. Riverside species, on the other hand, need lime-free soil, damp to very wet. Only in the case of the two Japanese species should the soil dry out in summer.


Bulbous-rooted irises may be divided when they are lifted in summer. Rhizomatous-rooted species are also increased by division. Older sections, without eyes, are discarded. Riverside plants may be divided in spring.

Bulbous-rooted irises

Iris danfordiae: Height 10-15 cm; flowers in early spring. Iris hollandica hybrids, Dutch iris: Height 50-70 cm; flowering season late spring; chiefly blue, yellow with orange etc. Marketed on a large scale as cut flowers. Iris reticulata: Height 15 cm; dark-purple or blue flowers in early to mid spring.

Iris xiphioides, English iris: Height 50 cm; flowering season early to mid summer; the flowers are larger and flatter than those of the Dutch iris. Rhizomatous-rooted irises

Iris cristata: Height 15-20 cm; lilac-blue flowers with a yellow crest in late spring and early summer. Keep out of full sun.

Iris germanica, bearded iris: Height 30-80 cm; flowering season late spring and early summer. Magnificent large flowers in a variety of colours and colour combinations. Consult a good catalogue.

Iris pumila: Height 10-15 cm; flowering season mid to late spring. Looks like a miniature Iris germanica. Strains in a variety of colours. Waterside plants

Iris kaempferi, Japanese iris: Height 60-100 cm; flowering season mid to late summer as magnificent flat, open flowers. A large number of garden forms. Iris laevigata: Height 50 cm; blue flowers in mid to late summer; resembles the previous species. Iris pseudacorus, yellow flag: Height to 2 m; yellow flowers in late spring and early summer. Iris sibirica: Height 70-100 cm; blue, rose-red or white flowers in early summer. A robust border plant.

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