Spring onions are the garnish you always run out of — and one of the easiest crops to never buy again. A packet of seed sown thickly gives months of fresh bunches, they grow happily in pots on a windowsill, and you can even regrow new plants from the bases of supermarket spring onions. For near-zero effort, few crops give so much.
This guide covers sowing thickly from March to September, succession sowing for continuous supply, overwintering varieties for spring harvests, and the regrow-from-scraps trick. Written for Central and Western Europe, no experience assumed.
| Care point | What spring onions need |
|---|---|
| Sun | Full sun to partial shade |
| Water | Regular — keep the soil moist for tender stems |
| Soil & pH | Light, fertile, well-drained; pH 6.0–7.0 |
| Sow outdoors (Central Europe) | March–September (thickly, in succession) |
| Spacing | Sow thickly; thin to 2–3 cm apart |
| Days to harvest | 60–90 days from sowing |
| Difficulty | Very easy — sow and forget |
Step 1: Sow thickly — crowding is the point
Unlike most vegetables, spring onions like being crowded: sow seeds thickly in a drill 1–2 cm deep, about 1 cm apart, in rows 15 cm apart. Dense sowing keeps the stems slender and tender — widely spaced plants fatten into small bulb onions instead.
Thin only lightly, to about 2–3 cm apart, eating the thinnings as mini spring onions. Like leeks and onions, they are alliums — see our first vegetable garden guide for where they fit in your rotation.
Step 2: Succession sow every 3–4 weeks
One sowing gives one flush — so sow a short row every 3–4 weeks from March to September for continuous supply. Each sowing takes 8–12 weeks to reach picking size, so overlapping sowings keep you in spring onions from June to November.
This is the same little-and-often rhythm as lettuce and radishes. Mark each sowing with a label and date — by midsummer you will forget which row is which.
Step 3: Keep them watered and weeded
Spring onions have shallow roots and suffer fast in dry soil — drought makes stems tough and hot. Water regularly in dry spells, following our watering guide, and mulch between rows (see our mulching guide) to hold moisture.
Weed carefully: young onion seedlings are easily swamped and hard to tell from grass weeds. A clean, weed-free drill at sowing time saves hours later. They need no feeding beyond the compost in the bed.
Step 4: Harvest young and keep them coming
Pull spring onions when stems are pencil-thick — young and tender. Do not wait for them to fatten: oversized spring onions are just small bulb onions, tougher and hotter. Pull the biggest, leaving smaller ones to keep growing.
Harvest by pulling gently from loose soil, or loosen with a hand fork first. Rinse, trim the roots, and use within a few days — homegrown spring onions do not store, which is exactly why growing your own beats buying them.
Use the whole plant: the white base is mild and sweet (brilliant in stir-fries), the green tops are fresher and sharper (perfect as a raw garnish). Snipped tops regrow weakly if the roots are left in the ground — not a full second crop, but a bonus handful a week or two later.
Step 5: Sow overwintering varieties for spring
For spring onions in early spring, sow hardy overwintering varieties ('White Lisbon Winter Hardy') in August–September. They sit small through winter and take off in March, giving you the year's first pickings weeks before spring sowings catch up.
Cover autumn sowings with fleece in the coldest months in exposed gardens. This is the same overwintering trick as autumn onion sets and garlic — the garden working for you while you stay warm inside.
Step 6: Regrow from supermarket bases — free plants
Here is the trick: when you use shop-bought spring onions, save the bottom 3 cm with the roots and stand them in a glass of water on the windowsill (or plant straight into compost). Within days they sprout new green tops; within weeks you have usable spring onions again.
Regrown plants are never as vigorous as seed-grown ones, but they are free and instant — perfect for windowsill growing through winter when outdoor sowing stops. See our container gardening guide for more windowsill crops.
Step 7: Try perennial Welsh onions — sow once, harvest for years
If you love spring onions but tire of re-sowing, meet the Welsh onion (Allium fistulosum): a perennial that looks and tastes like a spring onion but comes back every year from the same clump. Plant it once, and divide the clump every 2–3 years to make free new plants.
Sow or plant Welsh onions in spring in the same way as ordinary spring onions, but instead of pulling the whole plant, snip the green tops and let them regrow — cut-and-come-again, like chard or kale. They are hardier than ordinary spring onions, shrug off winter, and flower attractively for pollinators if you let a few stems go. One corner of the garden devoted to a Welsh onion clump gives you garnish for a decade with almost no work — the ultimate lazy gardener's crop.
Troubleshooting: common spring onion problems
Stems fattening into small bulbs: Sown too thinly or left too long. Sow thickly, thin to 2–3 cm, and pull young at pencil thickness. Once bulbing starts you cannot reverse it — eat them as baby onions.
Tough, hot, fibrous stems: Drought stress or harvested too late. Water consistently and pull young. Hot weather makes all alliums hotter — autumn crops are milder.
White rot or mushy bases: Usually waterlogged soil or onion white rot (do not grow alliums there again for 8 years). Ensure good drainage; our soil basics guide covers fixing drainage.
Onion fly maggots in the stems: The allium family's pest — thin in the evening (crushed foliage attracts the fly), cover with fine mesh from sowing, and rotate alliums yearly. See our pests guide for organic defences.
What to do this October
October is last-sowing and overwintering month: your final outdoor sowing should already be in, and overwintering varieties sown in August–September need a fleece cover as nights turn cold. Keep pulling from late sowings while they last.
Start a windowsill regrow jar now — supermarket bases in water give you fresh tops through winter when the garden offers nothing. See the full October checklist for the month's other jobs.
Frequently asked questions
What is the difference between spring onions and bulb onions?
Spring onions are harvested young before bulbing (or are non-bulbing varieties); bulb onions are grown to full size. Sow spring onion seed thickly and pull young — that is the whole difference.
Can I grow spring onions indoors all winter?
Yes — regrown bases on a bright windowsill produce usable tops all winter. Seed-sown indoor crops work too in pots 15 cm deep, though they grow slowly in low winter light.
Why do mine keep going to seed?
Stress — usually a cold snap after sowing or drought. Sow after March, water consistently, and choose varieties suited to your sowing time. Bolted plants are still edible; pull and use them.
How many should I sow?
A 1-metre row sown thickly gives roughly 30–40 spring onions. A family that uses them regularly wants a metre sown every month from March to August.
Related guides
- How to Grow Onions: Plant Sets This Autumn — the allium family's main crop
- How to Grow Leeks at Home: Beginner's Guide — the tall allium for winter
- How to Grow Garlic: Plant in October, Harvest in Summer — plant it right now
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