Allium

What the allium family is

Alliums are a family of plants grown for their sharp, savoury flavour. The common kitchen-garden members are onions, shallots, garlic, leeks, spring onions and chives — plus ornamental cousins with their tall purple flower heads. We grow them for the part that does the work: the swollen bulb (onion, garlic), the blanched white stem (leek), or the slim green leaves (chives, spring onion).

They're a friendly group for beginners. Most are forgiving, store well, and several can be started from sets or cloves rather than fiddly seed.

What they need to grow

Alliums share a simple wish-list:

• Full sun and an open spot.
• Free-draining soil — they sulk and rot in cold, wet ground.
• No fresh manure. Don't plant into a recently manured bed; it encourages soft, leafy growth and rot. Improve the soil the autumn before instead.
• A firm, settled seedbed rather than a fluffy one.

Keep them weed-free, since alliums have thin upright leaves that cast little shade and are easily swamped.

Common problems

A few issues crop up regularly:

• Onion white rot — a soil fungus that yellows the leaves and rots the base with fluffy white mould. It lingers in the soil for years, so rotate crops and never replant alliums where it has appeared.
• Rust — orange spots on leaves, common on leeks and garlic in damp summers. Space plants for airflow and avoid wetting the foliage.
• Bolting — onions throwing up a flower stalk, usually after a cold snap. Bolted onions won't store, so use them first.

Their role in crop rotation

Alliums are one of the main groups in a four-bed rotation, kept apart from brassicas, roots, and legumes. Moving them to a fresh bed each year is the single best defence against white rot and other soil-borne troubles, since the diseases that target them build up where they grow repeatedly. As a bonus, many gardeners slot alliums in after legumes to use the nitrogen those crops leave behind.

UK planting notes

Timing matters in the British year:

• Garlic goes in during autumn (October–November) — it needs a cold winter spell to split into cloves.
• Onion sets are planted in spring (March–April), with some hardy types also planted in autumn.
• Leeks are sown in spring and transplanted in early summer for autumn and winter pulling.
• Spring onions and chives can be sown little and often from spring onwards for a steady supply.

For step-by-step instructions on individual crops, see the vegetable growing guides; chives sit happily among the herb growing guides too.