Sow and grow annual onions and shallots from seed

Save money by growing hundreds of onions and shallots for only a few pounds

I always sow our brown and red onions, as well as shallots, from seed shortly after the winter solstice to coincide with lengthening days. If you haven’t grown them from seed before, it can be hard to believe they’ll grow into fully harvestable vegetables by summer, but I promise you they will! Once you grow onions and shallots from seed, you will never go back to expensive onion sets (heat treated baby onion bulbs).

The main reason I grow the onion family from seed is to prevent introducing onion white rot into our soil. Onion white rot is a soil born fungus that attacks the roots of the onion family. Once it arrives, it’s impossible to remove and will destroy your onion crops forever more. It is transferred on living onion bulbs, like onion sets and garlic cloves - never plant garlic bought in supermarkets for this reason, only from reputable sellers that screen the bulbs, such as The Garlic Farm. Onion white rot however isn’t transferred by seeds.

Sowing onions and shallots is easy, sprinkle the seeds into shallow 0.5cm deep dips in a tray of peat free compost, spacing seeds roughly half a centimetre apart, in rows 5cm apart (as shown in the above photo). Label them as you go because it’s near impossible to tell the difference between onion and shallot seeds and seedlings when young, which is important when planting them out in spring.

Cover the seeds with compost, water a little and then keep moist on a sunny windowsill until they germinate. Once germinated, move them somewhere cool but sheltered outside. Such as a cold frame, unheated polytunnel or greenhouse. Onions and shallots are perfectly hardy, they just need the warmth at the start to germinate.

In spring plant them outside when winter breaks and frosts are less likely, a month or so after the spring equinox, so around mid-late April or early May. Carefully tease them out of the tray, they come away easily for me, and plant them to the same level in the ground in a sunny spot. Don’t damage the roots while doing this, they might be tangled but should gently pull away.

Space onions in rows outside about 10cm apart from each other and shallots 15cm apart. Leave 30cm between rows for easy hoeing and weeding. Water them in spring if we have a dry spring, though usually, they never need watering for me, they’re a very easy crop to grow.

If you’d like more information on growing onions and shallots, please see my longer guide to growing onions and shallots from seed.