What soil temperature do Onion need?

Onion germinate best when soil temperature is between 8°C and 30°C.

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), Red Globe.

What grows well with Onion?

Good companion plants for Onion include: Carrot, Beetroot, Lettuce, Chamomile, Strawberry.

When to Plant Onion in Melbourne, Cool Temperate Guide

Sow July to September. Right now in September you can sow.

Also called spring onion, scallion, shallot (the Australian name for spring onion).

Published 17 February 2026 · Last reviewed 11 August 2026 · By Garden Buddy
Growing advice is reviewed by hand. Planting dates, current conditions and prices on this page update daily.

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.

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.

Planting Calendar for Cool Temperate

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
-	-	-	-	-	-	S/T/D	S/T/D	S/T/D	-	-	-

S = Seed Tray T = Transplant D = Direct Sow

Want a nudge when it is Onion sowing time in Melbourne?

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.

Current Growing Conditions

Soil temperature: 13.1°C (optimal range: 8–30°C) ✓ Ready to plant

Modelled from Open-Meteo forecast (Melbourne), not a live sensor.

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.

Worth growing?

A 2.4 m × 1.2 m bed fits 72 plants, about $29 worth at today’s Aldi, Coles and Woolworths prices, checked today.

That is roughly 11 kg at $2.66 a kilo.

Draw your onion bed → No account needed.

Common Onion Pests in Cool Temperate Zones

Downy Mildew, risk: MODERATE (score: 42/100)

Organic prevention: Rotate allium crops on a 3-year cycle. Remove crop residues after harvest. Avoid planting near cereal crops which harbour thrips. Maintain weed-free beds.

View all pest alerts →

Where to next

What onion costs in the shops right now, retailer by retailer, updated daily.

Also worth sowing in the cool temperate zone this September: Ginger, Sweet Corn, Chilli Peppers and Snow Peas.

The pest most likely to find your onion: Botrytis / Grey Mould.

Supermarket Price

Current average retail: $2.66/kg (12-month range: $1.99–$5.20)

Grow your own and save on grocery bills.

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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): Apr, Jun to Jul
Subtropical (Brisbane): Feb, Apr to Jun, Aug
Warm Temperate (Sydney): Jul to Sep
Cool Temperate (Melbourne): Jul to Sep
Cold / Highland (Canberra): Aug to Sep
Arid / Semi-Arid (Alice Springs): Feb, Apr to Aug
Mediterranean (Perth): Jul to Sep

Does onion grow all year round in Melbourne?

No. In the Cool Temperate zone the planting months are Jul 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.

Which zone am I in?

Type your postcode into the box under the heading and the page 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.