How to grow bearded iris
Take a look at our comprehensive guide to growing bearded irises, with advice from Monty Don, Alan Titchmarsh and Claire Austin
The bearded iris (Iris germanica), is one of the most popular irises to grow. Bearing sword-like foliage and flamboyant blooms from May to June, it makes a striking addition to hot sunny borders. Each bloom is made up of large outer and inner petals, known as ruffs and falls, respectively. Bearded iris are so called because of the hairs growing along the centre of the falls.
How to grow bearded iris
Grow bearded iris in moist but well-drained soil in full sun. Make sure the rhizome us sitting above soil level and gets sun for most of the day - this will ensure it flowers reliably. Divide clumps every three years to prevent congestion.
In this short video, iris expert Claire Austin shares her top tips for growing bearded irises, including how to divide them and how to deal with snails.
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Where to plant bearded iris
Bearded iris enjoy a position of full sun. Avoid crowding them with other plants as the rhizome needs to be backed by the sun to encourage flowers. For this reason you often find a bed dedicated to just iris.
They’ll grow well in a neutral, well-drained soil. A south-facing border with the protection of wall is ideal.
How to plant bearded iris
Bearded iris can be planted in autumn or spring. If you've bought potted plants, make sure they're planted at the same depth as they were in the pot. If purchased as a bare rhizome, soak the rhizome in water for a few minutes before planting.
If planting in a poorly-drained soil, dig in some horticultural grit to improve drainage. Plant so the top of the rhizome is just above the soil surface. Position the rhizome facing south if possible. Water plants in well.
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In this clip from Gardeners' World, Monty Don demonstrates how to plant bare-root and pot-grown bearded irises:
How to care for bearded iris
After flowering, deadhead plants as you may be lucky and get a second flush. In autumn tidy up the evergreen foliage by trimming it back to about 15cm.
Keep iris beds well weeded as shading from weeds will not be beneficial. Feed plants with a general purpose fertiliser in spring.
Divide plants every third year.
How to propagate bearded iris
Divide bearded iris every third year for the good of the parent plant and to create more plants. The heart of a mature iris can become woody and unproductive after a few years.
After flowering lift the rhizome with a garden fork. Cut off the healthy, young rhizomes at the edge of the plant and discard the woody centre. Replant the new plants immediately and cut back the foliage to about 12cm. This prevents the plants from being rocked about in the wind.
Here, Monty Don explains how to divide congested bearded irises:
Growing bearded iris: problem solving
Bearded iris can suffer from rhizome rot. As with all rotting things, the rhizome will start to smell and the base of the leaves will turn yellow. You may not spot the problem until you see foliage collapsed on the ground. The best way to cure this fungal problem is to cut out and discard sections of the affected growth. The problem tends to be worse in humid and hot conditions.
Bearded iris can also be affected by iris leaf spot, a fungal disease. Fungal spores are easily spread in wet weather and enter through damaged leaves. Minimise the risk by clearing away leaf debris from around plants, and avoid damaging leaves and stems unnecessarily.
In this video, Alan Titchmarsh explains why your bearded iris might not be flowering, and what you can do to solve the problem.
Great bearded iris varieties to grow
- Iris ‘Before the Storm’ – the blackest iris on offer. Flowers in May or June reaching about 90cm in height
- Iris ‘Bluebeard's Ghost’ – a lightly scented white flower with blue beards. Flowers in May or June. Reaches a height of 35cm
- Iris ‘Bold Print’ – white flowers with a ruffled blue-purple edging. Reaching 75cm when in flower in early June
- Iris ‘Sable' – inky blue flowers in July offering fragrance. Reaches a height of 75cm
- Iris ‘Susan Bliss’ – an old variety with lilac flower in June. Height 80cm