Stinking iris

Stinking iris: how do you recognise it?

Habit

Clump of upright to arching leaves, about 60 cm tall and 60 cm wide.

Leaves

Narrow, sword-shaped, glossy dark green and evergreen; they smell unpleasant when crushed.

Flower

Fairly small, greyish-violet to lilac with dark veins (pale yellow in var. citrina), June–July.

Fruit

Fat green seed pods that split into three in autumn to reveal bright red to orange seeds.

Roots

A creeping rhizome; the clump spreads slowly.

Flowering: June–July · Plants: March–April and September–October · Pruning: March

Why grow it?

• Evergreen leaves that form a fresh clump all year round.
• Bright red seeds in splitting pods from October into winter: a rare colour in the winter garden.
• One of the few plants happy in dry shade under trees and shrubs.
• Grows in sun, partial shade or full shade, in almost any well-drained soil.
• The seed pods are lovely in winter arrangements and dried displays.
• Little work: removing old leaves once a year is enough.

Stinking iris: where does it grow best?

• Sun, partial shade or full shade; in deep shade it flowers less and forms fewer seed pods.
• Almost any well-drained soil: sand, loam or clay, acid to chalky.
• Dry to moderately moist: once established it copes well with drought, even under trees.
• Allow 45–60 cm between plants.

Light

Sun, partial shade and shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

0.6 m tall, 0.6 m wide

Hardiness

Hardy (to -20 °C)

Goes well with

• Stinking hellebore: Another evergreen for dry shade, with pale green flowers in late winter.
• Barrenwort: An evergreen ground cover under trees.
• Male fern: A tough fern that also tolerates dry shade.
• Lesser periwinkle: Low, evergreen ground cover with blue flowers in spring.

Stinking iris: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole a little wider than the root ball and loosen the soil; under trees, mix in some compost.
3. Set the rhizome just below the surface, at the same depth as in its pot.
4. Space plants 45–60 cm apart.
5. Water straight away and again during dry spells in the first year, especially under trees.

Care

Watering

In dry spells during the first year; after that it is rarely needed.

Feeding

Not needed; in poor soil add some compost in spring.

Old leaves

In March, cut brown and damaged leaves off at the base.

Seed pods

Leave them until they are empty in late winter, or cut a few for an arrangement.

Seedlings

It sometimes self-seeds; leave the seedlings or move them while small.

Tip: Plant it where you can see it from the house in winter: the bright red seeds stand out best against the dark leaves when the rest of the garden is bare.

Stinking iris: when to prune it?

Pruning months: March.

When: It needs hardly any pruning. In March, remove old leaves and empty seed stems.

How:

• In March, cut brown, torn or frost-damaged leaves off at the base.
• Cut off old seed stems once the seeds have dropped or been eaten.
• Wear gloves: the sap can irritate the skin.

Caution: Do not cut back healthy evergreen leaves: the plant needs them.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September: cut pieces of rhizome with a fan of leaves from the edge of the clump and replant them straight away; shorten the leaves by half to reduce drying out.

Seed

Sow the red seeds in autumn, fresh from the pod, in pots and stand them outside; they germinate slowly and erratically, sometimes only after a year.

Stinking iris: how does it get through the winter?

Hardy to −20 °C.

• Hardy to about −20 °C: normally no protection is needed in Belgium.
• Evergreen: the clump and the open seed pods are at their best in winter.
• After a severe winter the leaves may be brown; cut them off in March and the plant will regrow.
• In a pot: stand it against a wall in severe frost.

Diseases and pests

• Few seed pods: In deep shade it flowers less, and without flowers there are no seeds. Give it a slightly lighter spot.
• Leaf spot: Brown spots on the leaves, especially in a wet summer. Cut off affected leaves.
• Rhizome rot: In wet soil the rhizomes rot and the leaves go limp. Plant in well-drained soil.
• Slugs: They eat young leaves and sometimes the flowers. Pick them off in the evening.

Through the year

• January: Red seeds decorate the garden.
• February: Leave the clump and seed pods standing.
• March: Cut off old leaves and empty seed stems. Plant or divide.
• April: Plant.
• June: Flowering begins.
• July: In flower. Water young plants in dry spells.
• September: Plant or divide. The seed pods swell.
• October: The seed pods split open. Plant. Sow seed.
• November: Cut seed pods for a winter arrangement.
• December: Red seeds in the winter garden.

Edible and useful

Not edible. All parts of stinking iris are poisonous, especially the rhizome and the seeds. In autumn the seed pods split open to show glossy, bright red seeds that stay all winter and tempt children; they are popular in dried arrangements too. Eating them causes vomiting, stomach ache and diarrhoea, in dogs and cats as well. Cut off the pods where young children play, or put the plant at the back of the border, and hang dried arrangements with the seeds out of their reach. The name comes from the smell of a bruised leaf, which recalls roast meat, hence its other name, roast-beef plant. The sap can irritate the skin: wear gloves when dividing and trimming. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• In English it is also called roast-beef plant: some people think the crushed leaves smell of roast beef.
• It is one of only two irises native to Britain; the other is the yellow flag.
• The open seed pods have long been used in winter arrangements and dried displays.