Allium giganteum · Amaryllidaceae

Giant Onion

⚠️ Not safe for petsDeciduous life cycle with annual flowering.80 to 120 cm

LightFull sun

WaterModerate, avoid waterlogging

DifficultyMedium

ColdWithstands light frosts down to minus 5 degrees Celsius.

Full sunModerate, avoid waterloggingMediumWithstands light frosts down to minus 5 degrees Celsius.

Description & origin

The giant onion is an ornamental plant known for its large spherical purple flower heads. Ideal for gardens, it reaches impressive heights and blooms in late spring. Its leaves are long and narrow but disappear before flowering.

Size

Can reach up to 120 cm in height under ideal conditions.

Foliage

Deciduous foliage, disappears before flowering.

Flowering

Blooms in late spring with large purple flower heads.

Detailed care

Light

Prefers full sun for optimal growth.

Soil

Well-drained soil rich in organic matter.

Watering

Moderate watering, avoiding waterlogging.

Temperature

Tolerates slightly negative temperatures but prefers mild climates.

Fertilising

Fertilize in spring with a balanced fertilizer.

Repotting

Transplant bulbs every 3-4 years to revitalize growth.

Pruning

Remove wilted flowers to encourage new blooms.

Propagation

Propagates by bulb division in autumn.

Common problems

Bulb rot

Occurs in poorly drained soils, causing bulb deterioration.

Rust

Fungal disease affecting leaves, causing orange spots.

Aphids

Insects that suck sap, weakening the plant.

Uses & curiosities

In the garden

Flower borders
Ornamental mass plantings
Pollinator attraction

Other uses

Ideal for dried floral arrangements

Did you know…

Despite its name, the giant onion is not edible like common onions. It is primarily grown for its ornamental beauty.