How to grow onions in a raised bed

Onions are a long, slow, easy crop — in the ground for months, but almost no trouble, and a raised bed's loose mix grows lovely clean bulbs.

Quick facts

• Position: full sun
• Spacing: 10 cm apart
• Tub depth: our 23 cm or 35 cm depth
• Time to harvest: 5–7 months

When should I plant onions?

Onions are day-length sensitive, so match the variety to your area and plant from autumn through winter for most of Australia. Plant seedlings or sow direct. Our free garden calendar shows the right months for your postcode.

• Subtropical (Brisbane & SEQ): March to July
• Temperate (Sydney, Melbourne, Adelaide, Perth): February to August
• Cool & mountain (Tasmania, Canberra, highlands): February to June and August to October
• Tropical (Cairns, Darwin): April to June
• Arid inland: March to July

How do I grow onions in a raised bed?

Plant into loose, well-drained mix and keep the bed weed-free — onions don't like competition. Don't bury the bulb; let its shoulders sit at the surface.

How often should I water and feed onions?

Water steadily while the tops grow, then ease right off once the bulbs are swelling and the tops start to fall — that dry finish helps them store.

What pests attack onions?

Keep an eye out for thrips and aphids. Most are easily managed — see our safe pest guide.

What diseases affect onions?

The main ones are downy mildew and rust. Good airflow, morning watering and steady moisture prevent most.

What grows well with onions?

Onions and other alliums help mask carrots and beetroot from pests; keep them away from beans and peas. See our companion planting guide.

When do I harvest onions?

Harvest when the tops flop over and yellow. Lift on a dry day, and cure them in an airy, shaded spot for a couple of weeks before storing.

Plan your patch: our free garden calendar shows what to plant now where you live. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: JLPC, CC BY-SA 3.0, via Wikimedia Commons.