Dutch iris

Dutch iris: how do you recognise it?

Habit

Slender bulb with a stiff, straight flower stem of 50–60 cm and few leaves.

Leaves

Narrow, grooved and grey-green; they often appear in autumn and die back in July.

Flower

Elegant iris flower of 8–10 cm with three drooping and three upright petals, in June.

Colour

Blue, violet, white, yellow, bronze or two-tone, with a yellow or orange blotch on the drooping petals.

Bulb

Small, oval bulb with a smooth, brown tunic, which forms offsets.

Flowering: June · Plants: September–November

Why grow it?

• One of the best cut flowers you can grow yourself: long, sturdy stems and a crisp, elegant flower.
• Brings fresh blue, white and yellow accents to the border in June, between the spring and summer flowers.
• Takes up little room: you can tuck it between perennials or grow it in rows in a cutting bed.
• Bumblebees and bees crawl into the flowers in search of nectar.
• Inexpensive bulbs that are easy to plant and quick to flower.

Dutch iris: where does it grow best?

• Full sun in a warm, sheltered spot, for example in front of a south-facing wall.
• Well-drained soil: sand, loam or light clay, neutral to chalky.
• Dry to moist; in summer the soil may be dry so the bulbs can ripen.
• Plant 8–10 cm apart, in groups or in rows for cutting.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

0.6 m tall, 0.1 m wide

Hardiness

Half hardy (to -12 °C): protect it in harsh winters

Goes well with

• Peony: Flowers in June and adds volume next to the slender irises.
• Lupin: Colourful spikes at the same time.
• Catmint: A soft blue base that hides the yellowing leaves.
• Ornamental onions: Purple globes that flower just before and during the irises.
• Love-in-a-mist: An airy annual around the stiff iris stems.

Dutch iris: when and how to plant it?

Plant in September–November.

1. Plant in September–November, preferably early, so the bulbs make roots before winter.
2. Loosen the soil and, on heavy ground, work in coarse sand or fine gravel.
3. Set the bulbs 10 cm deep, pointed end up.
4. Keep 8–10 cm between bulbs; in a cutting bed the rows can be 20 cm apart.
5. Firm the soil and only water if the ground is very dry.
6. In hard frost, cover the bed with a layer of straw, leaves or fleece.

Care

Watering

In a dry spring, water until after flowering; then keep it dry.

Feeding

In March, a thin layer of compost or some organic bulb fertiliser.

Cutting

Cut the stems when the bud shows colour; they open by themselves in the vase.

Foliage

After flowering, leave the leaves until they turn yellow so the bulb can recharge.

Lifting

On wet soil, or if flowering declines after a few years: lift in July, store dry and replant in autumn.

Tip: Plant a row of Dutch irises in your vegetable plot or cutting bed and cut them when the bud shows colour: that way you have a fresh bunch for the vase every week in June.

Dutch iris: when to prune it?

When: The Dutch iris is not pruned. You only cut flowers for the vase and remove spent stems.

How:

• Cut spent flowers with their stem, but leave as many leaves as possible.
• Let the leaves die back naturally in July.
• Clear the dead foliage once it is completely yellow and dry.

Caution: When cutting, do not take all the leaves: the bulb needs them to flower next year.

Pruning calendar and basic rules

Propagation

Offsets

Lift the bulbs in July, once the leaves have died back. Separate the small bulbs, store them dry and plant them in a separate bed in autumn; they flower after one or two years.

Dutch iris: how does it get through the winter?

Hardy to −12 °C: protect in harsh winters.

• Moderately hardy, to about −12 °C: in a warm, dry spot it survives most Belgian winters.
• The leaves often appear in autumn: cover the bed with straw, leaves or fleece in hard frost.
• Wet soil in winter is more dangerous than frost: make sure drainage is good.
• In a pot: stand the pot against a wall in winter and protect it in hard frost.

Diseases and pests

• Bulb rot: Bulbs fail to sprout or turn soft in wet soil. Plant in a drier spot or lift the bulbs every summer.
• Black marks on the bulb: Ink disease: black streaks on the bulb and yellowing leaves. Throw away affected bulbs and plant healthy ones in a different spot.
• Virus: Streaked or mottled leaves and flowers with streaks. There is no cure: remove the plant and control aphids, which spread the virus.
• Few flowers: After a few years the bulbs often produce fewer flowers. Lift them in July, let them ripen dry, or replace them with new bulbs.

Through the year

• January: Cover the bed in hard frost.
• March: Remove the covering. Give compost.
• May: Flower buds appear. Water in dry spells.
• June: In flower. Cut stems when the bud shows colour.
• July: Foliage dies back. Lift bulbs if needed and store them dry.
• September: Plant bulbs 10 cm deep.
• October: Plant bulbs. The first leaves appear.
• November: Plant the last bulbs. Have covering material ready.

Edible and useful

Not edible. All parts of these bulbous irises are poisonous, especially the bulb: eating any causes vomiting, stomach ache and diarrhoea, and dogs and cats fall ill from it too. In autumn the small bulbs look like shallots or onion sets: do not store them with the kitchen onions, plant them straight away and clear up empty bags and loose bulbs. Dogs that dig easily bring them up, and dwarf irises in a pot indoors are often at a child’s height. People who cut a lot of flowers or plant a lot of bulbs sometimes get red, itchy skin from the sap: wear gloves and wash your hands afterwards. If an animal has eaten some, call your vet. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• In Greek mythology Iris is the goddess of the rainbow, a reference to the many colours of the genus.
• Florists sell Dutch irises all year round: the bulbs are kept in cold storage and brought into flower in glasshouses.
• Unlike the bearded iris, the Dutch iris grows from a true bulb, not a rhizome.