Onion Sets

Onion Sets

Sow: September – November or February – April, depending on the variety and whether you’re planting seeds or sets
Harvest: May onwards, depending on the variety
Conditions: Well-drained soil in full sun.

Planting onion sets is easier than planting onion seeds. They grow faster, need less care and the success rate is higher but they’re also more expensive (£1.49 for 50 sets, £1.89 for 300 seeds), don’t keep like seeds do and there’s less of a choice in terms of variety.

SEEDS: Sow your seeds about 1/4 inch deep, 2 inches apart. When the seedlings have appeared, thin them out until they’re about 2 inches apart. You could also sow them in a propogator and plant the bulbs out when ready.

SETS: Plant each bulb 1 inch deep and 5 inches apart.

If you have to prepare the soil for your onion patch, do so two or three months in advance by digging in some well-rotted compost. Once in, keep the area weeded and the soil moist but not wet and the onions should take care of themselves. Once the foliage starts to turn brown, stop watering as this will help the onions to ripen and two weeks later, they should be ready to harvest. Wait for a dry day, then lift the bulbs with a fork.

Onions will need to be dried before storage, so leave them somewhere warm and dry for a week or so before getting them ready to store.

TIP: To avoid problems with pests and rot, plant your onions in a different spot every year.


Onions need quite a bit of space so growing in containers can be tricky. You could grow one onion per pot (approx. 5-6 inches in diameter) but in order to get a decent crop from a single tub, it will need to be about 8 -12 inches deep and wide enough to allow 2-3 inches between bulbs. You might also consider the fact that in order to keep yourself in onions for as long as possible, you’ll need to be careful about how many pots you’ll need in order to correctly stagger your planting.

If planting onions in pots, make sure you place them in a sunny position and pay attention to the soil. Onions need to be damp but not wet so check the soil regularly and water carefully, especially once the weather turns dry.


Remove the foliage and inspect the onions. Any that are damaged or soft need to be kept away from the rest, as they’ll reduce the storage life of the rest of the crop. You can still use them, just keep them separately.

Hang the onions upside down to dry, then wrap each onion in newspaper and store somewhere dry and dark. Alternately, keep them hung up in net bags or braided together (make sure you don’t remove the foliage if you plan to do this) to let the air circulate. Kept properly, they should store for between two and six months.

Companion Planting:

GOOD: Broccoli, Cabbage, Carrots, Tomatoes

BAD: Beans, Parsley, Peas


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