Dalmatian iris

Dalmatian iris: how do you recognise it?

Habit

Fan-shaped clump about 80 cm tall and 45 cm wide, growing from thick, creeping rhizomes.

Foliage

Sturdy, sword-shaped, blue-grey and arranged in a fan, 30–50 cm long; striped cream in the variegated forms.

Flower

Large lavender-blue flowers 8–12 cm across with a small beard, in May and June, scented of vanilla and grape.

Scent

The flowers smell softly of vanilla and grape; the dried rhizomes smell of violets.

Roots

Thick, fleshy rhizomes that lie half at the surface.

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

Why grow it?

• Soft lavender-blue, fragrant flowers in May and June: a garden classic.
• The blue-grey, sword-shaped foliage is ornamental all season, even without flowers.
• Very drought-tolerant, ideal for warm, dry spots and poor soil.
• The variegated forms are lovely foliage plants in a sunny border.
• Almost maintenance-free and long-lived.

Dalmatian iris: where does it grow best?

• Full sun: in shade it hardly flowers and can rot.
• Well-drained soil: sand or loam, neutral to chalky. Heavy, wet clay is unsuitable.
• Dry to average: it tolerates drought extremely well, but not standing water.
• A warm, sunny, sheltered spot, for example in front of a wall or on a sunny slope.
• Space plants 40–45 cm apart, with the rhizomes pointing outwards.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry

Size

0.8 m tall, 0.45 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Lavender: Scent and colour that go well together in a sunny border.
• Sage: Blue-purple spikes that match the blue flowers.
• Ornamental grasses: Fine stems as a soft backdrop.
• Hardy geranium: Blue or pink flowers in the same style.
• Stonecrop: A low, drought-tolerant plant for the sunny front.

Dalmatian iris: when and how to plant it?

Plant in July–September.

1. Plant in July, August or September, shortly after flowering, when the soil is dry and warm.
2. Dig a shallow hole and mix in sand or grit if the soil is heavy; compost is not needed.
3. Lay the rhizome shallow, so that the top sits half above ground and gets the sun; the roots go down.
4. Leave 40–45 cm between plants and point the leaf fans outwards.
5. Cut the leaf fan back to about a third and water once.
6. Do not mulch over the rhizome: it must be able to dry in the sun.

Care

Water

In dry weather during the first year; after that rarely or never. Too much water causes rot.

Feeding

Little or none. Too much nitrogen gives floppy foliage and rot; a little bone meal or lime is enough.

Deadheading

Cut the flower stems off at the base after flowering.

Keep rhizome clear

Keep the top of the rhizome free of soil and mulch, so it can dry.

Dividing

Divide every three to four years after flowering; this keeps it flowering.

Tip: Plant the rhizome shallowly in a sunny, dry spot and let the top sit half out of the ground: it is the best insurance against rot, and so against failed flowering.

Dalmatian iris: when to prune it?

Pruning months: June and October.

When: After flowering in June, cut off the spent stems; in October clear away dead or spotted leaves.

How:

• Cut the spent flower stems off at the base, just above the rhizome.
• Remove dead or brown leaves in autumn or at the end of winter.
• When dividing or replanting, cut the leaf fan back to about a third.

Caution: All parts are poisonous, especially the rhizome. Wear gloves: the sap can irritate the skin.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In July–September, after flowering, lift the clump and split it with a sharp knife into pieces with a leaf fan and a piece of rhizome. Discard old, woody parts. Replant shallowly.

Seed

Sow seed in autumn; it germinates slowly and unevenly. Plants flower only after 2–3 years and do not always resemble the parent.

Dalmatian iris: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy to about −25 °C: no protection is needed in Belgian winters.
• The foliage partly stays; cut away only dead or spotted leaves.
• Wet winters are the greatest risk: make sure the soil drains well.
• In a pot: put it against a warm wall and make sure the water can drain away.

Diseases and pests

• Rhizome rot: The rhizome turns soft and smells; the foliage collapses. Cut away rotten parts with a clean knife and replant in a drier spot.
• Leaf spot: Brown spots on the leaves in damp weather. Cut off affected leaves and clear dead foliage in autumn.
• Slugs: They eat young leaves and flowers in spring. Pick off slugs or lay a barrier of crushed shells.
• No flowers: Usually too much shade, planted too deep, too much nitrogen or a clump that is too dense. Move or divide it.

Through the year

• March: Clear away dead foliage. Watch for slugs.
• April: The leaves grow. Watch for slugs.
• May: Flowering begins.
• June: Flowering. Cut off spent stems.
• July: Plant or divide.
• August: Plant or divide.
• September: Plant or divide.
• October: Remove dead or spotted foliage.
• November: Tidy up.
• December: Dormant.

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?

• The dried rhizomes of the Dalmatian iris have been used in perfumery for centuries: after years of drying they smell of violets.
• ‘Iris’ is the Greek name for the rainbow and for the goddess of the rainbow, because of the many colours in the family.
• The variegated forms with cream stripes are popular foliage plants, even outside the flowering season.