Claude Monet loved to paint irises and you can understand why. The stiff stem and sword-shaped leaves are topped by ruffled flowers in every colour.
Different types of iris
There are around 300 species in the genus Iris. The most popular variety of irises for gardeners to grow is the spring-flowering bearded iris (Iris germanica), or German iris. Other popular irises include the Siberian iris (Iris sibirica), the hybrid Dutch iris (Iris x hollandica) and Algerian iris (Iris unguicularis).
Iris breeders have provided us with hundreds of varieties of bearded irises and they all have three upright standards and three falls. The falls are marked with orange beards and this flash of colour often brings the flower to life.
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Where to plant irises
Irises’ most important requirements are full sun and good drainage. They will survive on a range of soils, except heavy clay. Those with clay soil can add coarse grit and make a raised bed to improve drainage.
It's important for iris plants to not be overcrowded as without enough light they will not flower.
When to plant irises
Irises should be planted in early autumn.
How to plant irises
When planting irises, soak the rhizomes in water for an hour.
Prepare the ground well by digging in good garden compost.
Put the iris rhizome in the ground so that it faces the sun, with the foliage behind, spreading the roots outwards.
Space them between 9-12in apart (22-30 cm) and almost cover the rhizome with soil, leaving the upper part exposed. It will push up as it establishes.
Firm in and water well.
A bearded iris in Monet's garden, Giverny.
When irises bloom
Bearded irises flower at different times between April and June according to their variety.
Algerian irises flower in winter, Dutch and Siberian irises flower in summer.
Find out how to grow winter-flowering irises
When to cut irises back
Remove any browned leaves during the growing season to discourage leaf spot.
Cut off the flowering stems at the base once the flowers have faded.
When to divide irises
Propagate irises by dividing your clumps every third, fourth or fifth year to keep them vigorous, otherwise they may stop flowering.
The best time to divide irises is straight after flowering, but this can be done up until early September.
How to divide irises
Look for the new rhizomes - they are paler and firmer to the touch. Discard any old, dark pieces of root that feel soft.
Shorten the roots to make them easier to plant.
Trim the foliage to create a fan - leaving the leaves about six inches long (15cm). This is to prevent wind rock.
Replant in fresh ground or add some fertiliser or organic material.
Find out more about dividing perennials
Feed in the spring with a top dressing of a general fertiliser such as Growmore. A second top dressing of bone meal can be applied after flowering if you wish.
Once established, irises should not be watered or over fed. Over-feeding encourages rotting.
Deadhead irises after flowering by snapping off the stems near the base.
Pests and diseases
Normally bearded irises are trouble-free plants, however leafspot may be a problem after a spell of wet weather. You will see small brown spots on the leaves. They rarely do much damage but they are unsightly. Affected leaves should be cut back and burnt.
If the leaves turn yellow it may be root rot. Clean up the rot with a knife. Professional growers use a 10% bleach solution.
The shorter early-flowering bearded irises can be used on sunny edges of borders. But taller bearded irises need to get the sun to their toes - so a border edge or a dedicated iris border is best. But they need a dedicated space to allow the sun to get to the rhizomes - this produces more flowers.
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Bearded iris varieties clockwise from top right: 'Carnival Time', 'Dusky Challenger' and 'Edith Wolford'
Bearded iris varieties
Irises are divided according to height from the shortest miniatures to the tall bearded. The divisions are abbreviated and often listed by the name and they flower in sequence. The shortest first, the next tallest next etc.
Miniature Bearded Irises - MDB (8in, 10cm), flower in April
Standard Dwarf Bearded - SDB (8-15in, 20-38cm), flower in late April
Intermediate Bearded - IB (/ 16-27in, 41-70cm), flower in May
Miniature Tall Bearded - MTB (/16-27in, 41-70cm) flower in May
Border Bearded - BB (16-27in, 41-70cm), flower in May
Tall Bearded - TB (up to 39in, 1m), flower in June
Good bearded irises to plant
There are hundreds of varieties on offer and some have been chemically changed to become Tetraploid. These tend to have very large flowers and they almost look top heavy. You love them or you hate them!
Tall bearded irises
A two-tone blue iris with velvety navy-blue falls and pale-blue standards.
A pale-blue self (all one colour).
A softly ruffled pale-yellow and pastel violet-blue.
A ruffled dark iris - one of the best.
An informal white and violet ruffled iris.
Bright yellow standards supported by maroon-brown falls marbled in white veins close to the beard. Sophisticated.
An iris with a copper-coloured flower.
Shorter bearded irises
A very floriferous short iris with soft apricot flowers.
A sky-blue iris with greener leaves than most.
A maroon-brown and claret iris with ragged beards.
'Little Black Foot'
A dark-purple iris with soft-blue beards.
Iris ‘Torero’ (2005)
This French-bred iris from Cayeux in France was voted the best iris in a public competition in France. The apricot standards are underpinned by strawberry-red falls decorated with bright-orange beards.
It reaches a manageable 90 cm (3 ft) and it will need an open sunny situation and well-drained soil to display its dazzling livery to full effect. It’s one of 600 Cayeux varieties in a rainbow of colours.
Did you know...?
Their very name, Iris, signifies the Goddess of the Rainbow. She was able to unite and heaven and earth and the Ancient Greeks celebrated her by planting irises on the tombs of their loved ones.
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