Iris

Bearded Iris Flowers

These cottage garden classics are a diverse family of hardy bulbous and rhizomatous perennials, loved for their firm, upright stems of bright showy flowers.

Family: Iridaceae
Botanical Name: Iris
Common Names: Flags

Foliage: Deciduous, sword-shaped, grey/green leaves.

Flowers: Showy blooms on stout erect stems. Each bloom consists of two parts, three outer petals (falls) and three shorter inner petals (standards).

Flowering Period: Spring and summer (depending on variety).

Soil: Moist but well-drained, fertile soil (chalk, sand or loam). Acid or neutral pH. Bog and water Irises need moist damp conditions.

Conditions: Best in full sun, will tollerate some shade. Grown in a south, east or west facing aspect, in an exposed or sheltered possition.

Habit: Clump forming.

Type: Bulbous or rhizomatous-rooted perennials.

Origin: Europe, Russia, North Africa, Asia, America.

Hardiness: Most species are fully hardy in the UK.

Planting and Growing Irises

Irises are a large group of plants of diverse classification. There are two main forms, the bulbous group and the rhizomatous group. These can be further divided into five main types:

  • Bearded iris with hairy lower petals.
  • Beardless iris with smooth petals.
  • Crested iris (tender in the UK).
  • Bulbous iris (grown from bulbs).
  • Bog or water garden Irises.

Most are surprisingly easy to grow and make excellent cut flowers.

All forms tolerate acid or alkaline soils except I. kaempferi (a lime-hater) and I. germanica (an acid-hater). Most forms are best grown in a sunny position, except for I. unguicularis and I. foetidissima.

Dutch and Spanish species prefer a light, free draining, fertile garden soil. The English Iris requires a heavier soil. Tall bearded forms prefer a deeply dug fertile soil, with plenty of humus. Japanese Irises thrive in marshy land.

Taking Care of Irises

Regular division of all kinds of Iris is desirable to reinvigorate the plants.

Pruning

Unless collecting seed, cut back flowering stems once blooms have faded.

Pests and Diseases

Susceptible to attack by Iris sawfly and aphids. Prone to ink diseases, leaf spot, bulb or rhizome rot and fungal disorders.

Propagating Iris

Bulbous forms should be lifted and divided in the autumn.

Increase rhizomatous species either by seed sown in April under a cold frame or by division in August.

Divide Bearded Irises in the spring. Reduce the leaves by half and plant with the upper part of the rhizomes above the surface of the soil.

Clump-forming irises can be divided when dormant in winter.

Popular Varieties of Iris

There are irises suitable for all different types of soil and situation. Each has its own individual requirements, so check plant labels before planting.

Bearded Irises

Bearded irises are available in a wide range of colours and sizes, usually scented. Easy to grow and ideal for naturalising. They are drought tolerant once established. Large, green, sword-like leaves arise from a thick fleshy rhizome. For best results, plant with the top of the rhizomes just above soil level, where the sun can bake them and ensure a good flower display. Flowers May-June.

Iris chamaeiris is a dwarf bearded type with sword-shaped green leaves and large blue, purple, white, or
yellow flowers. Ideal for the rock garden. Height to 9in (22cm), spread to 6in (15cm).

Iris Germanica (German Iris) is a large classic summer flowering iris with stout, erect stems. Ideal for cut flowers. Average height 2 to 3ft (60 - 90cm), spread 2ft (60cm). Hundreds of hybrids are available, including: 'Ambassadeur' a tall variety with smoky bronze, dark velvety-maroon bicoloured flowers. Available from You Garden. Also 'Red Zinger' (rich red), 'Festive Skirt' (ruffled white petals with pink champagne falls), 'Loop de Loop', (white petals with purple/lavender ruffled edges) 'Senlac' (light purple flowers and darker purple falls), 'Nibelungen' (rich combination of cream, yellow and purple) and 'Rajah Brooke' (butter yellow petals and burgundy falls). Available as a mix from Gardening Direct. Another good form is 'Edith Wolford' (bicolour blue and yellow blooms). Available at Thompson & Morgan and Van Meuwen.

Iris pallida is a semi-evergreen rhizomatous form noted for its striking foliage and showy, fragrant mauve-purple flowers, in May and June. Height to 4ft (1.2m), spread to 1.5ft (45cm). One of the most attractive forms is 'Variegata' with fine variegated yellow and blue-green foliage. Available from Van Meuwen.

Beardless Irises

Iris orientalis is a perennial, beardless type with bright, sword-like leaves with bluish bloom. Produces bold yellow and white flowers in June-July. Likes moist conditions. Height up to 5ft (1.5m), spread to 2ft (60cm).

Iris setosa (bristle-pointed iris, Beachhead Iris) is rhizomatous perennial with the mid-green leaves and soft-blue flowers. Dwarf cultivar 'Baby Blue' has lavender-blue petals splashed with white at the centre. Height 8in (20cm), spread 12in (30cm). Available at Thompson & Morgan.

Iris sibirica (flag iris) has slender, grassy foliage topped with compact, bright-blue flowers, in June-July. A reliable, hardy perennial, perfect for naturalising and great for cutting. Prefers a damp position. Height to 3ft (90cm), spread 1ft (30cm). Good varieties include: ‘Cambridge’ (pale lilac with purple veining), 'Blue King' (royal blue), 'Silver Edge' (indigo flowers fringed with silvery blue. 'Tropic Night' has purple blooms with tawny gold and white falls. Available at Thompson & Morgan. For a mix of bight colours choose 'Peacock Mix' with its attractive ruffled, blousy blooms. Available from You Garden.

Iris UnguicularisIris unguicularis (syn. I. stylosa) has narrow grassy leaves topped with lilac or blue flowers, in November-March. Must have dry conditions. Useful for cutting. Height to 2ft (60cm), spread 1ft (30cm).


Iris versicolor (blue flag) has narrow, erect foliage and multiple stems bearing bluish-purple flowers. Good cultivars include 'Mysterious Monique' Available from Van Meuwen.

Water Irises

Iris ensata (Japanese water iris) is a beardless clematis-flowered iris with erect foliage and rich violet-purple flowers in June-July. Must have moist conditions. Height to 2ft (6cm), spread to 1ft (30cm). Good cultivars include: 'Belgium Warrior' Available from Van Meuwen. 'Caprician Butterfly' Available from Van Meuwen. Also 'Blue Mandarin' (purple-violet), 'Blue Heaven' (light blue-violet) and 'Light at Dawn' (white, flat flowers with purple picotee edging). Not to be missed area the ensata dinner plate cultivars, with impressive 6in (15cm) flowers, such as 'Blueberry Pie' (dramatic purple blooms), 'Ice Cream' (purple-lilac blooms edged in white) and 'Tirimasu' (white petals, edged with a mauve picotee margin). Available at Thompson & Morgan.

Iris laevigata (water iris, rabbit-ear iris) a true aquatic plant, available in different shades and combinations of blue, purple and white flowers. Height to 2ft (60cm), spread 1ft (30cm). Will grow in up to 9in (22cm) of water on the marginal shelf of a pool. Good varieties include: 'Colchesterii' (purple-blue and white mottled flowers), 'Rose Queen' (pink), 'Snowdrift' (white).

Iris pseudacorus (water iris), grows in water up to 18in (45cm) deep and has bright yellow flowers.

Bulbous Irises

Iris bucharica (Juno Iris, corn leaf iris, horned iris)) produces bright blooms of yellow and white from April. Height to 16in (40cm). Available from Van Meuwen.

Iris foetidissima (woodland iris, stinking iris) is a common evergreen perennial with glossy rich green leaves and insignificant yellow-tinged purple flowers, followed by bright orange seeds pods. Grows happily in deep shade under trees.

Iris danfordiae provides much need bright yellow flowers towards the end of winter, followed by narrow, grassy leaves. Height and spread 6in (15cm). Available from Van Meuwen.

Iris 'Eyecatcher' is an impressive new form with heavily patterned white petals with rich blue and a yellow stripes and dark blue freckles. Useful for patio pots, rockeries, window boxes and borders. Height to 8in (20cm). Available from Van Meuwen.

Iris histrioides (Turkey) produces short, stocky, bright-blue flowers, in January-February. Grassy foliage follows the flowers. The best form is 'Major'. Height and spread 6in (15cm).

Iris hollandica (Dutch Iris) is a hardy, easy to grow, garden favourite that produces strap-like, grey-green leaves and sturdy stems. Flowers appear in mid spring / early summer, in shades of blue yellow and white, depending on variety. One of the most popular cultivars is 'Mystic Beauty' which produces large blue flowers highlighted with bronze and yellow stripes, in June. Height to 18in (45cm)." Available from You Garden. 'Tiger Mixed' is a uniquely coloured Dutch iris with a lovely combination of purple and maroon petals, dashed with yellow accents. Available from Van Meuwen.

Iris latifolia (English iris - originated in the Pyrenees) is a tall upright form with narrow green leaves. Showy flowers July to August, in shades of white, blue or lavender. Height to 2ft (60cm).

Iris Reticulata Blue FlowersIris reticulata, is a popular rockery variety which flowers in early spring. Height and spread 4in (10cm). The deep violet-purple flowers produced in February-March amongst grassy green foliage. Available from Van Meuwen.