Growing onions, garlic & leeks
The allium family — onions, garlic, shallots, leeks and spring onions — are the quiet backbone of the veg patch. They take up little room, ask for little fuss, store for months, and flavour almost everything you cook. Better still, their pungent scent is a gift to their neighbours, muddling the pests that hunt by smell. A bed of alliums is about the most useful ground you can give over to anything.
This is the family overview — for full sowing dates and varieties of each, follow the links through to its own page.
One family, four easy crops
What unites the alliums is how little they need: an open, sunny spot, soil that isn't freshly manured (rich ground gives soft growth and storage problems), and not much competition from weeds. Each is started a slightly different way, which is the main thing to get right:
The easy way in — little immature bulbs you push into the soil in spring (or autumn for an early crop). Far simpler than seed.
Plant individual cloves in autumn — they need a cold spell to split into a full bulb. The easiest, most rewarding allium of all.
Sow in spring, transplant the pencil-thin young plants into deep holes, and they'll stand right through winter for digging as you need them.
Quick and undemanding from seed — sow a short row every few weeks through the season for a constant supply.
Planting & spacing
Onions & shallots from sets:push each set into soft soil so just the tip shows, about 10cm apart in rows 25–30cm apart. Firm them gently — birds love to tweak loose sets out, so check the row for a few days and re-firm any that pop up. Shallots are the same, but each one multiplies into a clump.
Garlic from cloves:split a bulb into individual cloves and plant them pointy-end up, 2–3cm deep and 15cm apart, in autumn. Use proper seed garlic rather than a supermarket bulb — it's certified disease-free and suited to our climate.
Leeks from seed: the clever trick is the deep hole. Once the seedlings are pencil-thick, make a 15cm dibber hole, drop a leek in, and simply fill it with water rather than soil. The hole blanches a long white stem as the leek swells.
Keeping them growing cleanly
- Keep them weed-free— alliums have wispy roots and hate competition. Hand-weed carefully so you don't nick the bulbs.
- Watch for allium leaf miner & onion fly— the modern scourge. Fine insect mesh over the bed at the key egg-laying times (spring and autumn) is the surest defence; companion-grown carrots help confuse onion fly too.
- Don't over-water— a steady supply while they bulk up, then ease off as they near harvest so they ripen and store well.
- Rotate them— alliums build up soil pests and white rot over time, so move them around your beds and never grow them in the same spot two years running.
They're wonderful companions, too — see companion plants for onions & garlic for what to grow alongside (and the one crop to keep them away from).
Lifting, curing & keeping
Onions and garlic tell you they're ready when the foliage flops over and yellows — resist the urge to bend the tops down yourself; let them do it. Ease the bulbs up with a fork and lay them out to cure: a fortnight somewhere warm, dry and airy (a greenhouse bench or a rack in the shed) until the skins are papery and the necks fully dry.
Cured properly, they keep for months in nets, trays or plaited ropes somewhere cool and dry — the real reward of the allium bed, a homegrown store that sees you through the winter. Leeks need no storing at all: hardy as they are, leave them in the ground and dig them fresh whenever you want one.
Common questions
Should I grow onions from sets or seed?
For most growers, sets are the easy choice — quicker, more forgiving and less pest-prone, and you just push them into the soil. Seed is cheaper with more variety and can give bigger bulbs, but needs an early indoor start and more care. Start with sets.
When do you plant garlic in the UK?
Mainly autumn, October to November. Garlic needs a cold spell to split a clove into a full bulb, so an autumn planting works best. You can plant in late winter or early spring too, but the bulbs are usually smaller.
How do you grow leeks?
Sow thinly in spring, grow on until pencil-thick, then transplant into deep 15cm dibber holes and water in (don't backfill) — the hole blanches a long white stem. They're hardy and stand all winter, so dig them as you need them.
How do I store onions and garlic?
Lift when the foliage flops and yellows, then cure them somewhere warm and airy for a couple of weeks until the skins are papery. Store cured bulbs cool, dry and airy in nets or ropes, and they'll keep for months.