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 Sydney?

Recommended varieties for the Warm Temperate zone include: Creamgold (intermediate-day), Brown Spanish (intermediate), Early Lockyer White, Red Burgundy, Gladalan Brown.

What grows well with Onion?

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

When to Plant Onion in Sydney, Warm 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 Warm Temperate zone, which takes in Sydney, Newcastle and Wollongong. Somewhere else? Your postcode picks the right one.

Not your zone? Cairns Brisbane Melbourne 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 Warm 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 Sydney?

One email a week with what is worth planting in the Warm 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: 17.0°C (optimal range: 8–30°C) ✓ Ready to plant

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

How to Grow Onion in Warm Temperate Australia

When to Plant

Sow March-May, transplant April-July. Intermediate-day varieties perform best. Some long-day varieties will work if planted early enough (March).

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

Warm Temperate Growing Tips for Onion

Recommended Varieties

Creamgold (intermediate-day)
Brown Spanish (intermediate)
Early Lockyer White
Red Burgundy
Gladalan Brown

Key Challenges

Getting timing right for day length response
Downy mildew in humid autumn/winter
Bolting in cold winters if plants are too large

Pro Tips

Intermediate-day varieties are the sweet spot for Sydney region
Sow seeds in March for transplanting in May-June
Avoid transplanting seedlings thicker than a pencil to reduce bolting risk

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 Warm Temperate Zones

Downy Mildew, risk: MODERATE (score: 57/100)

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 warm temperate zone this September: Ginger, Beetroot, Chilli Peppers and Cucumber.

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 Sydney?

No. In the Warm 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 Warm Temperate zone, Sydney is its reference city.