Allium atropurpureum

Allium atropurpureum: how do you recognise it?

Habit

Slender flower stem of 50–60 cm above a few leaves; barely 10 cm wide.

Leaves

A few strap-shaped, grey-green leaves that wither around flowering time.

Flowers

Flat to domed head of 5–7 cm with star-shaped, deep wine-red to almost black flowers, in May–June.

Fruit

Three-chambered capsules with black seeds; the dry heads last a long time.

Bulb

Small, round bulb of 2–3 cm; planting depth about 10 cm.

Smell

Bruised stems and leaves smell of onion.

Flowering: May–June · Plants: September–November

Why grow it?

• A rare, deep wine-red flower colour, lovely in contrast with silver foliage and pale colours.
• Bees and bumblebees visit the flowers in May–June.
• An elegant cut flower; the seed heads are good for drying.
• Takes up little space and fits between perennials and grasses.
• Easy and hardy: plant it in autumn and it returns every year.

Allium atropurpureum: where does it grow best?

• Full sun.
• Free-draining soil: sand, loam or clay, neutral to chalky.
• Dry to normally moist: in wet winters the bulbs rot. Mix grit into heavy soil.
• Space the bulbs 10–15 cm apart among low perennials that hide the dying leaves.

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

Hardy (to -20 °C)

Goes well with

• Lamb’s ear: Silvery-white, felted leaves that make the wine-red flowers stand out.
• Feather grass: Airy, pale stems around the dark heads.
• Catmint: Low blue flowers that hide the dying leaves.
• Woodland sage: Purple spikes at the same time, in the same dry, sunny spot.

Allium atropurpureum: when and how to plant it?

Plant in September–November.

1. Plant the bulbs in September–November, as long as the soil is not frozen.
2. Dig a hole or a wide pit about 10 cm deep; on heavy soil put a layer of grit in the bottom.
3. Set the bulbs pointed end up, 10–15 cm apart, preferably in groups of at least five.
4. Cover with soil and firm lightly; water only if the soil is bone dry.
5. Mark the spot with a stick so you do not dig them up by mistake before they emerge.
6. Keep the bulbs out of reach of children and pets before planting.

Care

Watering

Rarely needed; only in a very dry spring.

Feeding

Not needed in ordinary garden soil. On poor sandy soil, a little compost in March.

Leaves

Let the leaves die back naturally after flowering; this lets the bulb store food.

Deadheading

Leave the seed heads as decoration, or cut them off if you do not want seedlings.

Cutting

Cut the stems when the first flowers open and change the water often, or it will smell of onion.

Tip: Plant the bulbs about 10 cm deep among low plants with silver leaves, such as lamb’s ear: they hide the dying foliage and show off the dark flowers.

Allium atropurpureum: when to prune it?

When: No pruning is needed. After flowering you can cut off the spent stems; always let the leaves die back naturally.

How:

• Cut off spent stems if you do not want seed, or leave the dry heads as decoration.
• Only remove the leaves once they are completely yellow or brown.
• In late summer or autumn, simply pull the dry stems out of the ground.

Caution: Do not cut the leaves while still green: the bulb weakens and flowers less.

Pruning calendar and basic rules

Propagation

Offsets

After a few years the bulbs form small offsets. Lift the clump once the leaves have died back, separate the offsets and replant them in autumn.

Seed

Sow ripe seed in autumn in a pot left outdoors. Seedlings take 3–4 years to flower.

Allium atropurpureum: how does it get through the winter?

Hardy to −20 °C.

• Hardy to about −20 °C: in Belgium the bulbs can simply stay in the ground.
• Wet soil is the biggest danger: plant in a free-draining spot or mix grit into the soil.
• In a pot: stand it against a wall in winter, out of the rain, so the compost does not become waterlogged.

Diseases and pests

• Bulb rot: Bulbs that fail to come up or are soft in wet soil. Plant them in a drier spot or in gravel.
• Yellow leaves at flowering: Normal for ornamental onions. Hide the leaves behind low perennials and let them die back.
• Slugs: They eat the young leaves in spring. Pick them off in the evening.
• Rust: Orange pustules on the leaves. Remove affected leaves and choose an airy, sunny spot.

Through the year

• March: Leaves emerge. Compost on poor soil.
• April: Watch for slugs. Flower buds appear.
• May: Flowering begins.
• June: Flowering. Cut stems for a vase.
• July: The leaves die back. Collect seed or leave the heads standing.
• August: If needed, lift and separate offsets.
• September: Plant bulbs.
• October: Plant bulbs. Sow in a pot outdoors.
• November: Plant the last bulbs.

Edible and useful

Not edible. Ornamental onions are true alliums, related to onion, garlic, leek and chives, and like them they are poisonous to dogs and cats: all parts, especially the bulbs, contain sulphur compounds that damage the red blood cells and can cause anaemia. Cats are more sensitive than dogs, and the signs (lethargy, pale gums, red or brown urine) sometimes appear only after a few days. Horses, sheep and other livestock can fall ill from them too. Even though the leaves and bulbs smell of onion, they are not grown as vegetables: do not eat them, and never store the bulbs with the kitchen onions, as they are not meant for eating and may have been treated with pesticides. Do not plant them where your dog digs, keep loose bulbs out of reach of pets and children, and do not put a vase of alliums where your cat chews the stems. If your dog or cat has eaten a bulb or leaves, call your vet, even if it shows no signs yet. 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?

• Atropurpureum means dark purple.
• Ornamental onions are related to onion, garlic, leek and chives, and they too smell of onion when you bruise a leaf.
• The dry seed heads stand until autumn and are popular in dried arrangements.