How to grow Onions in the UK
Grown from 'sets' - tiny baby onions that you just push into the soil.
- DifficultyEasy peasy
- WhereBeds or Pots
- Grows to40cm
- Spacing10cm
- Time to first pickabout 18 weeks
When to sow, plant and harvest onions
| Sow outdoors | mid March to late April or mid September to late October |
|---|---|
| Pick | early June to mid September |
Dates are for central England. Sow about two weeks later in the north and Scotland, and up to two weeks earlier in the south and south west. Get the dates for your postcode.
Sowing it outdoors
- Snip off the dry wispy tip of each onion so birds have nothing to grab
- Push each little onion into the soil so only the very tip is showing
- Space the sets 10cm apart in the row, with rows 25cm apart
- Press the soil down firmly around each one
- Cover with netting or twiggy sticks for the first few weeks
- Water them in
- Stick in a label
Top tips for growing onions
- Birds like to pull sets out - snip off the dry wispy tops first, and push them back in if they do.
Looking after onions
- At planting: Check your onions - push any that have popped out back in
- Week 6: Pull out weeds around your onions - they hate sharing
Soil and feeding
Well-drained soil that doesn't stay wet. Add compost, and grit if your soil is heavy clay - onions and garlic rot if they sit in water. No fresh manure.
Pests and problems
- Blackbirds & sparrows: peck seedlings, pull out onion sets and steal ripe fruit
- Allium leaf miner: a tiny fly whose maggots tunnel into onion-family stems in spring and autumn
- Bend canes or plastic pipe into hoops over the row
- Stretch netting over the hoops, pulled tight so birds can't get tangled
- Peg or weigh down the edges so nothing can sneak underneath
- Check it every day
Harvesting and eating onions
When the leaves go yellow and flop over, lift them and leave them to dry in the sun.
How to eat them: Slice and fry slowly until soft and sweet - great in burgers.
Storing onions
Keeps 2-3 months for autumn-planted, up to 6 months for spring-planted.
- Dry them first until the necks are thin and papery
- Hang them in a net (or old tights, with a knot between each one!)
- Keep somewhere cool, dry and dark
Chop and freeze in bags for cooking. Keeps about 6 months.
Good varieties of onions
- Sturon: Reliable golden onions that store well.
- Red Baron: Sweet red onions, lovely raw in salads.
- Radar: Plant in autumn for onions in June.
- Centurion: Big, round, golden onions.
Companion planting
Grows well with
- Carrots: the onion smell hides carrots from carrot fly
- Beetroot: they grow at different depths, so share space well
Keep away from
- Peas: onions can stunt peas
- Broad beans: onions can stunt beans
- Runner beans: onions can stunt beans
- French beans: onions can stunt beans
Saving your own onions seed
.
- It's best to buy fresh, certified ones each year - saved ones can carry diseases that build up in the soil.
Things to build for onions
Where to buy onions seeds
Thompson & Morgan · Suttons · Amazon
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Onions questions
When should I sow onions in the UK?
In the UK, sow onions outdoors from mid March to late April or mid September to late October. These dates suit central England; sow about two weeks later in the north and Scotland and up to two weeks earlier in the mild south and south west.
When can I pick onions?
Onions is ready from early June to mid September. When the leaves go yellow and flop over, lift them and leave them to dry in the sun.
How long do onions take to grow?
Roughly 18 weeks from sowing or planting until the first harvest.
Are onions easy to grow?
Onions are rated 'easy peasy' for beginners, and can be grown in the ground or a raised bed or in pots and containers.
Plan your own garden: it tells you what to do and when, for your postcode.
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