Yellow horned poppy

Yellow horned poppy: how do you recognise it?

Habit

Upright, branching plant 40–60 cm tall and about 40 cm wide; a rosette first, flowering stems in the second year.

Leaves

Blue-grey, thick, deeply cut and hairy; the rosette leaves are up to 30 cm long, the stem leaves clasp the stem.

Flower

Poppy-like, 6–9 cm, with four soft yellow, papery petals, from June to September.

Fruit

A very long, curved, horn-shaped seed pod of 15–30 cm that splits open in late summer.

Roots

Deep, thick taproot: it tolerates drought but not transplanting.

Flowering: June–September · Sowing: April–May and September

Why grow it?

• Flowers from June to September with large, soft yellow poppy flowers.
• Blue-grey, cut foliage is decorative all year, even in winter as an evergreen rosette.
• Grows on poor, dry, chalky soil where other plants struggle.
• Bees and other insects visit the flowers.
• Self-seeds in gravel or sand and so returns year after year.

Yellow horned poppy: where does it grow best?

• Full sun in a warm, open spot.
• Poor, very free-draining soil: sand, gravel or chalky loam, neutral to chalky. Heavy clay does not work.
• Dry: it tolerates drought extremely well and rots in wet soil.
• A gravel garden, coastal-style border, green roof or sunny rock garden suits it best.
• Leave 40 cm between plants; it self-seeds, so leave room.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry

Size

0.6 m tall, 0.4 m wide

Hardiness

Hardy (to -15 °C)

Goes well with

• Sea holly: A coastal plant with blue-grey foliage and spiny flowers for the same gravelly soil.
• Sea kale: Big blue-green leaves and white flowers that suit a coastal style.
• Lavender: A fragrant, sun-loving neighbour for a warm, dry spot.
• Stonecrop: Low, drought-loving plants that cover the ground.
• Blue fescue: A blue-grey ornamental grass that echoes the colour of the foliage.

Yellow horned poppy: when and how to plant it?

1. Choose a sunny spot with lean, free-draining soil; on heavy ground mix plenty of coarse sand or grit into the top layer.
2. Sow in place in April–May or in September; it often germinates better after a cold spell.
3. Scatter the fine seed thinly on the soil, press down and barely cover, or not at all.
4. Thin the seedlings to 40 cm apart as soon as they are big enough.
5. Plant pot-grown plants with as little root disturbance as possible and keep the rootball intact: the taproot dislikes transplanting.
6. Water lightly until the seedlings or plants are established, and hardly at all afterwards.

Care

Water

Once established it needs no water. Wet feet are the greatest danger.

Feeding

Not needed: on poor soil it stays compact and flowers best.

Mulching

A layer of grit around the rosette keeps the foliage dry and prevents rot.

Self-seeding

Let a few seed pods ripen if you want it to come back. Remove them if you do not.

Deadheading

Cut off spent flowers to extend flowering, or leave them for the seed pods.

Tip: Sow it in place in poor sand or gravel: the taproot does not tolerate transplanting. Leave a few seed pods, because the plant is short-lived and so returns by itself.

Yellow horned poppy: when to prune it?

When: It does not need pruning.

How:

• Cut spent flower stems back to the rosette to extend flowering and limit self-seeding.
• Remove dead stems after flowering, or leave them for the seed pods.
• After flowering, remove the dried-out plant if it is not going to return.

Caution: Wear gloves when clearing or cutting back: the sap can irritate the skin and all parts are poisonous.

Pruning calendar and basic rules

Propagation

Seed

Sow in place in April–May or in September, thinly on lean soil. The seed often germinates better after a cold spell; the plant also self-seeds.

Collecting seed

In September, collect ripe seed pods before they split open and store them dry; sow the seed at once or in spring.

Yellow horned poppy: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Hardy to about −15 °C; the blue-grey rosette stays green in winter.
• The greatest danger is wet soil in winter: provide very free-draining soil or a layer of gravel.
• In a pot: use a deep pot with plenty of grit and stand it against a wall, out of the rain.

Diseases and pests

• Root rot: The rosette goes limp and brown. Usually caused by heavy, wet soil; provide free-draining soil and a layer of gravel.
• Slugs: They eat young seedlings in spring. Hand-pick or put down a slug barrier.
• Powdery mildew: White powder on the leaves, especially in damp weather. Provide space and a sunny spot.
• Aphids: Small insects on young shoots. Rinse off with water or let ladybirds clear them.
• Disappears after a few years: This is normal: the plant is short-lived. Let a few seed pods ripen so that new plants come up.

Through the year

• April: Sow in place. Thin seedlings.
• May: Keep sowing. Thin to 40 cm.
• June: Start of flowering.
• July: Full flower. No watering needed.
• August: Flowering. Seed pods form.
• September: Collect seed and sow. Clear dried stems.
• October: Rosettes stay green. Avoid wet soil.
• November: Rest. Check the layer of gravel.
• December: Rest.

Edible and useful

Not edible. All parts of these poppies are poisonous, especially the milky sap and the unripe seed heads: they contain alkaloids that cause nausea, vomiting, stomach ache and drowsiness if swallowed, in children as well as in dogs, cats and grazing livestock. They are not opium poppies: the poppy seed from the bakery comes from the opium poppy (Papaver somniferum), and the seed of these poppies is not eaten. Do not make tea from the flowers or seed heads, and hang dried arrangements with seed heads out of children’s reach. The sap can irritate the skin: wear gloves when cutting flowers for the vase, and keep the vase out of reach of small children and cats. 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?

• The seed pod can grow 15–30 cm long and resembles a horn; hence the name horned poppy.
• The genus name Glaucium comes from the Greek ‘glaukos’, blue-grey, after the colour of the foliage.
• The waxy, blue-grey foliage helps the plant cope with salt and drought on the coast.