• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Allium giganteum

giant onion

giant onion

© � RHS 1999

  • Other common names giant onion
    giant allium

  • Genus Allium are bulbous herbaceous perennials with a strong onion or garlic scent, linear, strap-shaped or cylindrical basal leaves and star-shaped or bell-shaped flowers in an umbel on a leafless stem

  • Family Alliaceae / Alliaceae

  • Details A. giganteum is a perennial with spreading, glossy, strap-shaped basal leaves which die down before the flowers. Dense globose umbels of bright purple flowers are borne on tall stems in summer

  • Plant range C Asia to NE Iran

Characteristics

  • Foliage Deciduous

  • Habit Columnar/Upright

  • Fragrance Leaf

  • Toxicity

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or North-facing or West-facing or East-facing

  • Exposure Sheltered

Soil

  • Chalk

    Chalk

  • Chalk

    Clay

  • Chalk

    Sand

  • Chalk

    Loam

  • MoistureWell-drained, Moist but well-drained

  • SoilChalk, Clay, Sand, Loam

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height

    1-1.5 metres

  • Ultimate spread

    0.1-0.5 metres

  • Time to ultimate height

    2-5 years

How to grow

Cultivation Easy to grow in fertile well-drained soil. Add grit when grown in clay soils to improve drainage

Propagation Propagate by seed, sowing in containers in a cold frame when just ripe or in the spring. Alternatively, remove offsets in autumn

Suggested planting locations and garden types Flower borders and beds Cut Flowers Cottage & Informal Garden

How to care

Pruning No pruning required

Pests Generally pest free

Diseases Generally trouble-free: Onion white rot and a downy mildew may occur

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