When to Plant Onion in Melbourne — Cool Temperate Guide
Photo: Wikimedia Commons
Onions are a staple in Australian kitchens and one of the most widely grown alliums in home gardens. Bulb formation is triggered by day length, making variety selection critical based on latitude. Short-day types suit northern Australia, while long-day types perform best in southern regions.
Current Growing Conditions
Soil temperature: 21.9°C (optimal range: 8–30°C) ✓ Ready to plant
How to Grow Onion in Cool Temperate Australia
When to Plant
Sow May-July for long-day varieties. Transplant July-September. Harvest December-February. Autumn sowing of overwintering varieties (March-April) for early summer harvest.
- Soil
- Well-drained, fertile loam enriched with compost. Avoid heavy clay or freshly manured soil which causes forking and soft bulbs.
- pH Range
- 6.0-7.0
- Sunlight
- Full sun (minimum 6 hours direct)
- Spacing
- 12cm apart, 30cm between rows
- Watering
- Consistent moisture during bulb development. Water deeply once or twice weekly. Reduce watering as tops begin to fall over (curing signal). Overhead irrigation can reduce thrips but increases fungal r
Companion plants: Carrot, Beetroot, Lettuce, Chamomile, Strawberry
Avoid planting near: Beans, Peas, Asparagus, Sage
Cool Temperate Growing Tips for Onion
Recommended Varieties
- Pukekohe Long Keeper (long-day)
- Creamgold (intermediate)
- Brown Spanish
- Ailsa Craig (long-day)
- Red Globe
Key Challenges
- White rot is a serious and persistent problem
- Downy mildew in cool, damp winters
- Onion maggot damage to spring plantings
Pro Tips
- Long-day varieties produce the largest bulbs in Melbourne's latitude
- Use insect netting to exclude onion fly from spring plantings
- White rot: if you have it, consider growing in containers with fresh soil
Harvesting Onion
When ready: Tops fall over naturally and begin to yellow. Bulb skin is papery and dry. Neck tissue is thin and soft. Do not push tops over prematurely as this reduces storage life.
How to harvest: Loosen soil with a fork and lift gently. Do not pull by the tops. Lay on their side in the garden for 1-2 days if weather is dry, then move to a well-ventilated, shaded area for 2-4 weeks to cure fully. Roots and tops are trimmed after curing.
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