Growing Onion in Australia: The Complete Guide
Onion is an easy to moderate bulb & allium to grow, needing full sun with regular, taper before harvest watering.
We get asked about onion often enough that it's worth setting out the full picture here, beyond what fits on our printable card.
Day-length matters
Onions form bulbs in response to day length — short-day varieties for warmer zones, long-day for cooler ones. Getting this wrong means small or no bulbs.
Planting Onion
Method — sow seed or plant seedlings shallowly; choose a variety suited to your day length. Soil — loose, well-drained, weed-free. Timing — sow or plant in autumn to late winter depending on zone and variety.
Ongoing Care
Worth paying attention to:
- Keep beds weed-free — onions compete poorly with weeds.
- Water regularly, then stop 2–3 weeks before harvest.
- Feed lightly early on; avoid nitrogen once bulbing starts.
- Bend tops over gently once bulbing is well underway.
Problems to Watch For
Keep these points in mind:
- Onion thrips — silvery leaf streaking; blast off with water, encourage predators.
- White rot — soil-borne; rotate beds for years if it appears.
- Bolting — cold snap after planting; plant at the right time for your zone.
- Splitting bulbs — inconsistent watering.
When and How to Harvest
Signs — tops yellow and fall over, necks soften. Method — lift with a fork once most tops have fallen. Curing — cure 2–3 weeks in a warm, airy, shaded spot until necks are papery. Storage — cool, dark, ventilated. Keeps 4–8 months.
For the condensed, printable version of everything above, head to the main onion guide page.