Garden flowers

Ornamental allium

AlliumAmaryllidaceae
Also: Allium
AT A GLANCE
Full sun Water: little H6down to −20 °C 0.4–1.2 m tall · 15–30 cm wide In a pot: yes
Flowering · UK
Flowering · Northern Italy
Flowering · Central Italy
Flowering · Southern Italy and islands

Plant deeply on a layer of grit at the base of the hole in heavy soil, to prevent rot before the bulb establishes.

Care

Light

Full sun.

Water

Drought-tolerant, dislikes wet summer soil.

Soil

Free-draining, even poor soil; performs well on chalky or alkaline ground.

Pruning

Not applicable — deadhead, or leave seedheads standing for architectural interest and wildlife, then cut foliage back once fully yellowed.

Feeding

Very little needed: a light general feed as the leaves come through, on soil that drains freely. Rich, damp ground is a bigger risk than an unfed bulb — it rots them.

Propagation

Lift and separate the offsets clustered round the parent bulb once the foliage has withered. Many also seed themselves freely; the seedlings take three or four years to flower but cost nothing.

Month by month

Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.

  1. JuneLeave seedheads standing through summer if a longer season of interest is wanted.
  2. JulyCut back foliage once fully yellowed. how ›
  3. OctoberPlant bulbs this month.

Months based on climate: UK. Your choice stays on this device.

  1. JuneLeave seedheads standing through summer if a longer season of interest is wanted.
  2. JulyCut back foliage once fully yellowed. how ›
  3. OctoberPlant bulbs this month.

Months based on climate: Northern Italy. Your choice stays on this device.

  1. JuneLeave seedheads standing through summer if a longer season of interest is wanted.
  2. JulyCut back foliage once fully yellowed. how ›
  3. OctoberPlant bulbs this month.

Months based on climate: Central Italy. Your choice stays on this device.

  1. JuneLeave seedheads standing through summer if a longer season of interest is wanted.
  2. JulyCut back foliage once fully yellowed. how ›
  3. NovemberPlant bulbs this month.

Months based on climate: Southern Italy and islands. Your choice stays on this device.

Common problems

Onion white rot

How to spot it. Soil-borne, affects all Allium.

What to do. Avoid replanting in infected ground for several years.

Slugs

How to spot it. On young shoots.

What to do. Protect emerging growth.

How to spot it. Orange pustules in humid summers.

What to do. Remove affected leaves.

Popular varieties

Allium ‘Gladiator’AGM1–1.2 m × 20 cm · May–JuneMay–JuneApril–MayApril–May
Allium ‘Purple Sensation’AGM75–90 cm × 15–20 cm · May–JuneMay–JuneApril–MayApril–May

Questions

Ornamental allium: is it hardy?

H6: Hardy in the vast majority of UK gardens. It survives down to −20 °C.

Can it grow in a pot?

Standard bulb container culture.

Ornamental allium: when do you prune it?

Not applicable — deadhead, or leave seedheads standing for architectural interest and wildlife, then cut foliage back once fully yellowed.

Ornamental allium: when does it flower?

In the climate of UK it flowers in May–June.

When do you feed it?

Very little needed: a light general feed as the leaves come through, on soil that drains freely. Rich, damp ground is a bigger risk than an unfed bulb — it rots them. Feeding months, UK: April.