When to Plant Onion in Melbourne, Cool Temperate Guide
Also called spring onion, scallion, shallot (the Australian name for spring onion).
Soil temperature is modelled from Open-Meteo forecast (Melbourne), not a live sensor.
What this month normally looks like in Cool Temperate
In October the Cool Temperate zone normally runs 19°C by day and 8°C overnight, with about 67 mm of rain over 9 or 10 wet days. The coldest October night on record across the zone was -3.0°C, so a late frost is not out of the question. Averages 1991 to 2026, 28 postcodes, SILO.
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This Onion guide is written for the Cool Temperate zone, which takes in Melbourne, Hobart and Geelong. Somewhere else? Your postcode picks the right one.
Not your zone? Cairns Brisbane Sydney Canberra Alice Springs Perth
Also handy: will it frost this week? and what grows in shade.
- Planting window
- Mar to Sep
- Days to harvest
- about 13 weeks
- Sun
- Full sun
- Water
- Regular
- Spacing
- 12 cm apart
- Soil pH
- 6.0–7.0
- Shop price
- $2.75/kg
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.
Published · By GardenBuddy.au
Planting dates, current conditions and prices on this page update daily.
Photo: Wikimedia Commons
Planting Calendar for Cool Temperate
- Jan -
- Feb -
- Mar S/D
- Apr S/D
- May S/T/D
- Jun S/T/D
- Jul S/T/D
- Aug T/D
- Sep T
- Oct -
- Nov -
- Dec -
S = Seed Tray T = Transplant D = Direct Sow
Want a nudge when it is sowing time?
One email a week with what is worth planting in the Cool Temperate zone right now, Onion included, plus which veg has jumped in price at the supermarket. Free, and you can stop it in one click.
How to Grow Onion in Cool Temperate Australia
- Soil
- Well-drained, fertile loam enriched with compost. Avoid heavy clay or freshly manured soil which causes forking and soft bulbs.
- Salt
- Sensitive. Struggles with salty bore water or salty soil. Give it rainwater if you can.
- 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 risk.
- Good companions
- Lettuce, Carrot, Dill, Beetroot, Cabbage
- Keep away from
- Asparagus, Cowpeas, Lentils, Peas, Sage, Snake Beans, Snow Peas
- Grow before it
- Fruiting crops (Tomato, Capsicum, Zucchini)
- Grow after it
- Legumes (Beans - Dwarf, Peas, Broad Beans)
Give the bed 3 turns before alliums go back in. Onion, garlic and leek like a lean bed and clean up after the heavy feeders.
Cool Temperate Growing Tips for Onion
Recommended Varieties
- Pukekohe Long Keeper (long-day)
- Creamgold (intermediate)
- Brown Spanish
- Ailsa Craig (long-day)
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
Pests and problems for Onion in Cool Temperate
- Botrytis (Grey Mould) Watch
- Thrips Watch
- Damping Off Watch
- Downy Mildew Downy mildew in cool, damp winters Watch
- Wireworms Watch
- Rust Watch
- White Rot The single most important disease to prevent. Never introduce infected sets or transplants. Clean tools between beds. Rotate alliums on the... Watch
- Basal Rot Avoid mechanical damage to bulbs. Plant in well-drained soil. Minimise soil disturbance near roots. Handle harvested bulbs carefully. Store... Watch
- Onion maggot Onion maggot damage to spring plantings Watch
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.
Storing and preserving onion
How to keep it
- Curing and Dry Storage. After harvest, cure in a warm (25-30C), dry, well-ventilated area for 2-4 weeks until neck is completely dry and outer skins are papery. Trim roots and tops. Store in mesh bags, plaited braids, or slatted crates in a cool (5-10C), dry, dark location with good airflow. Keeps: 3-6 months for most varieties; long-keeper types up to 8-10 months.
- Dehydrating. Peel, slice into 3-5mm rings or dice. Spread on dehydrator trays. Dry at 55-60C for 6-12 hours until completely brittle. Grind dried onion into powder or store as flakes in airtight containers. Keeps: 12 months in airtight containers, cool dark place.
- Freezing. Peel and dice. Spread on a baking tray and open-freeze for 2 hours. Transfer to freezer bags, removing as much air as possible. No blanching required. Frozen onions become soft when thawed. Best for cooking only. Keeps: 8-12 months.
- Pickling. Peel small onions or quarter larger ones. Salt and stand overnight. Rinse. Pack into sterilised jars. Cover with boiling pickling vinegar (malt or white wine vinegar with spices). Seal immediately. Allow 4-6 weeks to develop flavour. Keeps: 12 months sealed; 4 weeks once opened (refrigerated).
- Caramelised Onion Preserve. Slowly cook sliced onions in olive oil with a pinch of salt for 30-45 minutes until deeply golden. Add a splash of balsamic vinegar. Pack into sterilised jars. Refrigerate or process in a water bath (15 minutes). Keeps: 3-4 weeks refrigerated; 6 months if water-bath processed.
Grow vs buy
A 2.4 m × 1.2 m bed fits 72 plants, about $30 worth at today’s Aldi, Coles and Woolworths prices, checked today.
That is roughly 11 kg at $2.75 a kilo.
Draw your onion bed → No account needed.
What onion costs in the shops right now, retailer by retailer, updated daily.
What members get
- Soil and weather from your nearest station
- An email when it's time to sow
- Your own garden plan, including planning from a photo
- Price history and price alerts
- Pest risk alerts for your area
- Full salt and canning detail
Common Questions About Onion
When do you plant onion in Australia?
It depends on your climate zone, not the calendar month alone. Planting months by zone:
- Tropical (Cairns): Mar to Jul
- Subtropical (Brisbane): Mar to Jun
- Warm Temperate (Sydney): Mar to Aug
- Cool Temperate (Melbourne): Mar to Sep
- Cold / Highland (Canberra): Apr to Sep
- Arid / Semi-Arid (Alice Springs): Feb to Aug
- Mediterranean (Perth): Mar to Sep
Can you grow onion all year round in Melbourne?
No. In the Cool Temperate zone the planting months are Mar to Sep. Outside that window it either bolts, sulks or gets cut down by the weather.
What else is onion called?
Onion is the usual Australian name. Overseas seed packets and recipes call it spring onion, scallion, shallot (the Australian name for spring onion). Same plant, same growing advice.
When should I plant Onion in Melbourne?
Sow early types in March to April and long-day types such as Brown Spanish in June to August. Bulbs take six to eight months and are lifted when the tops fall over.
What soil temperature do Onion need?
Onion germinate best when soil temperature is between 8°C and 30°C.
How do I know when Onion are ready to harvest?
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.
What are the best Onion varieties for Melbourne?
Recommended varieties for the Cool Temperate zone include: Pukekohe Long Keeper (long-day), Creamgold (intermediate), Brown Spanish, Ailsa Craig (long-day).
What grows well with Onion?
Good companion plants for Onion include: Lettuce, Carrot, Dill, Beetroot, Cabbage.
Are onion salt tolerant?
No. Onion are salt-sensitive, one of the more sensitive veggies. Use rainwater if your bore water is salty, or grow them in a raised bed of fresh mix if your soil is.
Which zone am I in?
Type your postcode into the box near the top of the page and it tells you, and links this crop in your own zone if it differs. Or look it up on the grow zone map. This page is the Cool Temperate zone, Melbourne is its reference city.