Bearded iris

Bearded iris: how do you recognise it?

Habit

A clump of flat leaf fans on thick, creeping rhizomes; flower stems up to 80 cm, the clump about 45 cm wide.

Leaves

Sword-shaped, grey-green and stiff, in flat fans. They last until autumn, then partly die back.

Flower

Large, with three upright petals and three drooping petals carrying a hairy beard. Several buds per stem, in May–June.

Scent

Many varieties have a sweet scent, especially on warm, sunny days.

Rhizome

Thick, fleshy and horizontal, partly above ground. It grows outwards, so the centre of an old clump goes bare.

Colour

White, yellow, orange, pink, blue, purple, brown and almost black, often two-toned or veined.

Flowering: May–June · Plants: July–September · Pruning: June–July and October

Why grow it?

• Spectacular flowers in May–June, in more colours and combinations than almost any other perennial.
• Many varieties are beautifully scented, especially on a warm day.
• Very drought-tolerant: once established it hardly ever needs watering.
• A fine cut flower: in the vase the buds on a stem open one after another.
• The grey-green, sword-shaped leaves give the border structure long after flowering.
• Long-lived and easy to propagate by dividing the clump.

Bearded iris: where does it grow best?

• Full sun, at least six hours a day: the rhizomes need to bake in the sun, otherwise it flowers poorly.
• Well-drained sandy or loamy soil; acid, neutral and chalky soils are all fine.
• Dry to normally moist. Wet soil, especially in winter, makes the rhizomes rot.
• Put it at the front or middle of a sunny border, in a gravel garden or on a bank, away from large neighbours that shade it.
• Allow 40–45 cm between plants.

Light

Sun

Soil type

Sand or loam

Acidity

Not fussy

Moisture

Dry or normal

Size

0.8 m tall, 0.45 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Lavender: Likes the same sunny, dry spot and carries on flowering after the iris.
• Catmint: A soft blue cloud beside the clump that hides the bare stems after flowering.
• Sage: Purple spikes in June next to the broad iris flowers.
• Ornamental onion: Round flower heads that open at the same time and take up little space.
• Oriental poppy: Flowers in the same period and also likes sun and drought.

Bearded iris: when and how to plant it?

Plant in July–September.

1. Plant in July, August or September, shortly after flowering, so the roots establish before winter.
2. Dig a shallow hole and make a small mound of soil in the centre.
3. Lay the rhizome flat on the mound and spread the roots down on either side.
4. Fill in with soil until the roots are covered, but leave the top of the rhizome just above the surface.
5. Space plants 40–45 cm apart with the leaf fans facing outwards. Trim the leaves to 15 cm so the wind cannot rock the plant loose.
6. Water well once to settle the soil. Do not mulch over the rhizomes.

Care

Watering

Only in the first weeks after planting and in long droughts. An established clump rarely needs water.

Feeding

Usually unnecessary. Avoid manure and fresh compost: they make the leaves soft and encourage rot. On poor sandy soil a handful of low-nitrogen fertiliser in March is enough.

Mulching

Do not mulch: it keeps the rhizomes damp and shaded. Keep them free of weeds and fallen leaves.

Spent flowers

Snap off faded flowers and after flowering cut the whole stem off at the base. Leave the leaves: they feed the rhizome for next year.

Support

Tall varieties can fall over in wind or rain; in an exposed spot a cane per flower stem helps.

Dividing

Every four years, when the centre of the clump goes bare and flowers less (see propagation).

Tip: Never plant too deep: the top of the rhizome should sit just above the soil and bake in the sun. An iris planted too deep makes leaves but no flowers.

Bearded iris: when to prune it?

Pruning months: June–July and October.

When: In June after flowering for the flower stems, in July–August when dividing for the leaves, and in October for dead foliage.

How:

• After flowering, cut the flower stems off just above the rhizome.
• Leave the green leaves as long as possible: they build up reserves for next year’s flowers.
• When dividing or replanting, trim the leaves at an angle to about 15 cm.
• In autumn, remove brown, dead leaves: slugs and fungi then have fewer places to hide.

Caution: Do not cut green leaves short in summer for no reason: it weakens the plant and costs flowers.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

Every four years in July or August, after flowering. Lift the clump, break or cut off young pieces of rhizome with a healthy fan of leaves and discard the old, leafless centre. Let the cuts dry in the sun for a day before replanting.

Seed

Possible, but seedlings rarely resemble the parent and only flower after a few years. Mainly for those who enjoy breeding their own.

Bearded iris: how does it get through the winter?

Hardy to −30 °C.

• Very hardy, to about −30 °C: even in harsh Belgian winters no protection is needed.
• Wet soil is more dangerous than frost. Make sure drainage is good and do not cover the rhizomes with leaves or mulch.
• Freshly planted pieces can be lifted by frost; firm them back in spring.
• It also grows in a large pot with gritty compost; keep the pot dry in winter, for example against a sunny wall.

Diseases and pests

• Rhizome rot: The rhizome turns soft, brown and smelly; the leaves fall over. Cut out rotten parts back to healthy tissue, let the wound dry in the sun and move the plant to a drier spot.
• Few or no flowers: Usually too much shade, planting too deep or an overcrowded clump. Move it into sun, replant higher or divide.
• Leaf spot: Oval brown spots with a yellow edge, mostly in wet summers. Cut off affected leaves and clear up in autumn.
• Slugs: They eat young leaves and flower buds. Remove hiding places and pick them off in the evening.

Through the year

• January: Rest. After hard frost, check that young plants have not been lifted.
• March: Remove brown leaves and weeds around the rhizomes. A handful of low-nitrogen fertiliser if needed.
• April: Watch for slugs on the young leaves.
• May: Flowering begins. Cut flowers for the vase as soon as the first bud shows colour.
• June: Flowering. Cut spent flower stems off at the base.
• July: Divide old clumps and plant new rhizomes. Trim the leaves of the divisions to 15 cm.
• August: Divide and plant. Water until the divisions are established.
• September: Last month for planting.
• October: Remove dead leaves.
• November: Tidy up. No mulch on the rhizomes.

Edible and useful

Not edible. All parts of bearded iris and Dalmatian iris are poisonous, especially the rhizome: it causes a burning feeling in the mouth, vomiting, stomach ache and diarrhoea, in dogs, cats and grazing livestock too. Dried and aged for years, the rhizome becomes orris root, used in perfume, pot-pourri and some gins, and babies were once given a piece of orris root to chew when teething. Do not make it yourself: the fresh rhizome is poisonous and irritates mouth and stomach, and a baby can choke on a piece of root. The rhizomes sit half above the soil: watch out for dogs that chew them, and clear up the pieces when you divide the clumps. The sap can irritate the skin: wear gloves when dividing and cutting back. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• Orris root is made from the dried rhizome of some irises: after a few years of drying it smells of violets and is used in perfume.
• In Greek mythology Iris was the goddess of the rainbow: a fitting name for a plant with so many colours.
• The beard on the drooping petals guides insects to the nectar and pollen.