All About: Onion & Shallot Sets

Burford Garden Company
Burford Garden Company

Versatile and packed with flavour, onions and shallots are easy to nurture either in vegetable plots or containers. A gardener's favourite, there are many options to choose from for growing, so there is the divine opportunity to delve into the details, depending on your requirements. The flavour, disease resistance and harvesting time can differ among these varieties, as well as some of the more specific care requirements, so do take the time to read up on your choices before digging in.


Onions and shallots are often grown from “sets”, small bulbs grown from seed in the previous season, as they grow more reliably and swiftly with minimal maintenance. Slow-growing and requiring several months in the ground prior to harvesting, they thrive in fertile, well-drained soil, and it is advised that you do not plant them in the same place for consecutive years. If the pH is lower than 6.5, add lime.

Sowing indoors

If your soil is still too damp or cold in the spring (or you’re a keen early bird!), you can begin sowing your onion sets indoors between September - October. Shallots can also be sown indoors from late winter, but only from a seed.

  • Fill trays with a peat-free, multi-purpose compost and plant, before storing in an unheated greenhouse or sunny windowsill.
  • As the weather warms come spring, you can then transplant them outdoors. (As tempting as it may be, if you move them outdoors too early, this could lead to your sets bolting. Wait until the soil has warmed a little before planting out).
Sowing outdoors

Place the bulbs in drills or pushed into loose soil, with the tip just visible on the surface. Upon doing so, firm the soil around the bulb and water generously.

  • For maincrop onions, plant between March – April, 2cm deep with a planting distance of 5-10cm and a row spacing of 30cm.
  • For shallots, plant between February – March, 2.5cm deep with a planting distance of 15-20cm and a row spacing of 30cm.
Burford Garden Company
Burford Garden Company

Sowing shallots in drills


During extended dry periods in the summer, make sure to water your sets every fortnight. However, in the case of onions, once they have plumped up, stop watering. Remember to water in occasional doses of a general liquid fertilizer from spring to mid-summer to keep your vegetables boosted. Try to keep the area weed free and remove any flower heads as they start to form, to keep the energy focussed on swelling the bulb.


If you planted your onions in autumn, most of your sets will be ready for harvest by early to mid-summer. For those who opted for spring planting onions, in addition to shallots, anticipate your harvest from late summer to early autumn.

To ensure the best yield, it's crucial to pick your produce before the foliage dies completely. Once you notice the leaves turning yellow and collapsing, gently loosen the roots, lift the onion bulbs or clumps of shallots, and lay them on their sides, allowing them to bask in the sun to dry. If the weather is wet, bring them under cover and spread them out, preferably on dedicated racks.

For perfectly preserved onions, take an additional two weeks to let them dry before storing. Place them outdoors in full sunlight on wire racks, allowing air to circulate beneath. If the weather doesn't cooperate, consider a sunny greenhouse or a well-ventilated shed for the drying process.

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Onions ready to be harvested and stored

Burford Garden Company
Tips to bear in mind...

Do not allow your growing conditions to become overly damp, as this will potentially yield a host of fungal diseases. Make sure to blanket the area with fleece until they are rooted in, as birds are known to often peck newly planted sets out.