Onion sets 10 cm apart, shallots 20 cm, garlic 15 cm
Short answer
Plant onion sets 10 cm apart in rows 30 cm apart, with the tips just showing. Go to 15 cm apart if you want bigger bulbs. Shallots need 20 cm, because each set splits into a cluster, and garlic cloves go 15 cm apart and about 2.5 cm deep.
Onion sowing calendar
From the VegLog crop library. Change the frost dates to match your garden.
Last frost around 20 April, first frost around 31 October.
- Sow indoors
- late January to late February
- Sow outdoors
- early March to early April
- Plant out
- early March to mid-Aprilmid-September to mid-October
- Harvest
- early June to early September
Plant onion sets 10 cm apart in rows 30 cm apart. Push each one in so just the tip shows. For bigger onions, give them 15 cm. Shallots need twice the room, 20 cm apart, because each set splits into a cluster of eight to twelve bulbs. Garlic cloves go 15 cm apart and about 2.5 cm deep.
The plant spacing calculator shows how many fit in your bed, in rows or by the square foot.
Spacing at a glance
| Crop | Between plants | Between rows | Per 30 cm square | Depth |
|---|---|---|---|---|
| Onion sets | 10 cm (15 cm for big bulbs) | 30 cm | 16 | Tip just showing |
| Shallot sets | 20 cm | 30 cm | 4 | Tip just showing |
| Garlic cloves | 15 cm | 30 cm | 9 | About 2.5 cm of soil over the tip |
| Onions from seed, thinned | 10 cm | 30 cm | 16 | Seed 1 cm deep |
Spacing decides bulb size
Onions are one crop where spacing is a choice, not a rule. Each plant only grows as big as its share of light, water and food allows. Closer together, you get more onions but smaller ones. Further apart, fewer and bigger.
| Spacing | What you get |
|---|---|
| 5 cm | Small onions, good for pickling or roasting whole |
| 10 cm | Medium onions, the usual kitchen size |
| 15 cm | Large onions |
Rows 30 cm apart leave room to hoe. Onions have thin, upright leaves that don’t shade out weeds, so keeping the rows clear matters more than with most crops.
In raised beds and square foot gardens
You don’t need rows in a raised bed. Plant onion sets in a grid, 10 cm apart each way, which is sixteen to a 30 cm square. Shallots go four to a square, and garlic nine. Our square foot gardening chart has the grid for other crops.
Planting tips
- Trim off any long, dry papery tips before planting. Birds pull sets up by them.
- Push the set in gently, root plate down. Don’t screw it in, as that damages the roots.
- Firm the soil around it.
- Cover with netting or fleece until the sets have rooted, and push back any that get lifted.
Keep onions, shallots and garlic away from peas and beans, which they’re said to hold back. Carrots, beetroot and lettuce make good neighbours. For timings, see when to plant onion sets.
Questions people also ask
How deep do you plant onion sets?
Just deep enough that the tip shows above the soil, so the set is almost covered. Planted deeper, they're slower to grow; too shallow and birds and frost lift them.
How many onion sets per square foot?
Sixteen in a 30 cm square, in a grid of four by four. That gives medium bulbs. For larger ones, plant nine.
Can you plant onions close together for smaller onions?
Yes. Sets 5 cm apart give small onions that are handy for pickling or cooking whole. Spacing is the main way to control bulb size.
Dates set to your own frost dates
VegLog works out sowing and planting times for your town, then reminds you when each job is due.
