How to Grow

Optimum planting time: September – November

Flowers: May – June

Height: 30-120cm

Where to plant

Alliums, as members of the onion family, love full sun and fertile, well drained soil.

How to plant alliums in the ground

Allium bulbs are best planted in September and October while the soil is still warm, giving them a chance to start producing roots ready for flowering in spring.

  1. Choose a sunny spot with well-drained soil, as allium bulbs will rot if waterlogged. Clear any weeds and dig in some good quality compost to improve drainage on heavy soils.
  2. Using either a trowel or a bulb planter dig holes at least three times the depth of the bulb, approximately 10-15cm deep. Space smaller alliums such as ‘Purple Sensation’ 15cm apart. Large alliums like Allium cristophii or ‘Globemaster’ should be spaced 30-35cm apart.
  3. Place a bulb in each hole, making sure that the tip of the bulb is pointing upwards. Then fill the hole, firming the soil gently around the bulb.
  4. Water in after planting.

How to plant alliums in containers

Alliums make great container plants, allowing their spectacular displays to be enjoyed even in small spaces.

  1. Use a container that is deep and at least 35cm in diameter.
  2. Bulbs don’t like waterlogged soil, so place crocks (bits of broken pots) at the bottom of the pot to cover the drainage holes and stop them clogging up with compost.
  3. Fill the container with quality bulb compost or multipurpose compost to around 15cm below the rim.
  4. Place the allium bulbs on the compost with the tips of the bulbs pointing upwards.
  5. Cover with compost up to around 3cm from the rim of the container. Firm the compost down gently and water well.
  6. Place the container in a sheltered spot (e.g. against the wall of a house) over winter and move it to a sunny spot in spring.



  1. On poor soils, apply a balanced fertiliser like Growmore in spring.
  2. Alliums are reasonably drought-tolerant, but water container-grown alliums during any long dry spells in spring.
  3. Allium foliage usually dies back before the flowers are produced. If not, leave the foliage to die back naturally before removing it.
  4. Dried allium flowerheads can be deadheaded, cutting the stems back at ground level, or they can be left on the plant through summer to provide added interest in the border.
  5. Lift and divide crowded clumps of alliums after the flowers and leaves have died back.

Pests and Diseases

Alliums can suffer from onion white rot, downy mildew and onion fly, although ornamental onions tend to be less affected. If fungal diseases occur, pick off and dispose of infected leaves. Remove and destroy any severely affected plants.

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