Planting Onions

Onions can be direct sown in the garden, but starting them undercover can give them a head start. Plant seeds 0.5cm (1/4") deep along the row if direct sowing seeds or 10cm (4") apart if transplanting seedlings or planting sets, and 30cm (12") between rows. Onions prefer a well-draining soil rich in plenty of organic matter, and need full sun to fully mature correctly.

Growing Onions

If you started seeds undercover, plant out the seedlings after 4-6 weeks. If the seeds were direct sown, thin the seedlings out after the same amount of time. Onions don't provide much of an indication when they're lacking water, so be sure to maintain consistent watering and fertilise every few weeks with a nitrogen-rich fertiliser. Leaf production will cease and bulbing will begin once the onions start receiving 12 or more hours of sunlight a day. Once bulbs begin to develop, cover with a light layer of mulch to help retain moisture, leaving room around the bulb to discourage pests from nesting.

To protect from onion maggots and other pests, cover your onion crop with a fine mesh netting that won't block the sunlight, and seal it around the edges with soil.

Harvesting Onions

Onions are ready for harvest once the leaves are browned and have fallen over. Any onions that form flower stalks should be harvested immediately. Harvest by gently pulling the bulb from the ground, or digging if necessary. To store onions, allow the bulbs to cure in a warm area for 2-4 weeks. Once fully dried, trim the tops and store the bulbs in a cool, dry area.