How to Grow Onions from Sets
Updated: Oct 16, 2020
What are onion sets?
Onion sets are onion seeds that have been pre-grown to a mini bulb size and stored in special conditions.
Why use onion sets?
Onion sets allow quicker and easier results than planting from seed. Because they are pre-grown they establish more quickly. You'll also be able to harvest them earlier next year than onions grown from seed.
Why is it important that they are certified organic?
Non-organic sets may be sprayed with anti-fungals and other chemicals - and no-one wants to eat those!
When can I plant them?
Ideally plant between October and December, but you can get away with sowing as late as February! If growing over-wintering onions make sure to choose a site which will not become water-logged as this can cause them to rot.
How do I grow them?
Onions need a sunny, sheltered site with fertile, well-drained soil. Ideally add plant food before planting as onions are hungry plants! Plant onion sets as soon as possible after receiving to avoid losing any to mould/rot.
Gently push the onion sets into soft soil so that the tip is just visible.
Firm the soil around them.
Plant onion sets 5-10cm apart in rows 25-30cm apart
Or you can plant about 9 onion sets per square foot.
If you have a lot of bird visitors to your garden, cover with fleece until the roots are established so they are not stolen!
Mix potting soil and fertiliser into pots
Plant your organic onion sets about 5-10 cm apart just covering the tip.
Cover with an organic mulch - for example leaves, straw or bark
Place in a sunny position & feed regularly
How do I care for them?
The size of the onion depends on how many healthy green leaves it has, so if the weather is dry keep it happy with water and more feeding for the best harvest.
When do I harvest them?
Harvest early as scallions or leave to mature into full onions by May/June.
How do I harvest them?
When the onion top starts to fall over, stop watering and start harvesting!
Place the bulbs on a rack in full sun outdoors or a well-ventilated polytunnel for about two weeks. When the foliage is dry and papery, undamaged bulbs can be stored in a light, cool, dry place until needed.