When to Plant Onion in Perth, Mediterranean Guide

Sow March to September. Right now in October it is out of season. The next sowing month is March.

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

Planting window
Sow short-day onions from March to July and plant out through winter up to September. Bulbs mature from late spring into early summer.
Days to harvest
about 13 weeks
Sunlight
Full sun (minimum 6 hours direct)
Water needs
Consistent moisture during bulb development. Water deeply once or twice weekly. Reduce...
Spacing
12cm apart, 30cm between rows
Soil pH
6.0-7.0
Shop price
$2.41/kg average

Published · Last reviewed · By GardenBuddy.au
Growing advice is reviewed by hand. Planting dates, current conditions and prices on this page update daily.

This Onion guide is written for the Mediterranean zone, which takes in Perth, Adelaide and Bunbury. Somewhere else? Your postcode picks the right one.

Not your zone? Cairns Brisbane Sydney Melbourne Canberra Alice Springs

Also handy: will it frost this week? and what grows in shade.

Onion

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.

See what grows now in your own postcode

Planting Calendar for Mediterranean

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

S = Seed Tray   T = Transplant   D = Direct Sow

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

One email a week with what is worth planting in the Mediterranean 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: 15.6°C (optimal range: 8–30°C) ✓ Ready to plant

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

What this month normally looks like

In October the Mediterranean zone normally runs 22°C by day and 10°C overnight, with about 38 mm of rain over 6 or 7 wet days. The coldest October night on record across the zone was -0.2°C, so a late frost is not out of the question. Averages 1991 to 2026, 19 postcodes, SILO.

How to Grow Onion in Mediterranean Australia

When to Plant

Sow short-day onions from March to July and plant out through winter up to September. Bulbs mature from late spring into early summer.

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...

Companion plants: Carrot, Beetroot, Lettuce, Chamomile, Strawberry

Avoid planting near: Beans, Peas, Asparagus, Sage

Grow before, grow after

Onion belongs with the alliums, the roots and alliums turn of a four turn bed rotation.

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.

Mediterranean Growing Tips for Onion

Recommended Varieties

  • Pukekohe Long Keeper (long-day)
  • Creamgold (intermediate)
  • Brown Spanish
  • White Spanish
  • Red Globe

Key Challenges

  • Hot, dry spring causing premature bulbing if not established
  • Downy mildew in wet winters
  • Storage quality depends on thorough curing

Pro Tips

  • Perth and Adelaide latitudes suit long-day varieties well
  • Plant early enough for good leaf growth before bulbing starts
  • The dry summers are ideal for curing and storing onions

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 $26 worth at today’s Aldi, Coles and Woolworths prices, checked today.

That is roughly 11 kg at $2.41 a kilo.

Draw your onion bed → No account needed.

Where to next

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

Also worth sowing in the mediterranean zone this October: Lemongrass, Dwarf Beans (Bush), Eggplant (Aubergine) and Parsnip.

The pest most likely to find your onion: Thrips (Onion, Tomato, Western Flower).

Supermarket Price

Current average retail: $2.41/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:

Does onion grow all year round in Perth?

No. In the Mediterranean 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.

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 Mediterranean zone, Perth is its reference city.