When to plant Spring Onion in Tropical Australia

Tropical zone — applies to Darwin, Cairns, Townsville, Broome, Mackay and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Arid.

Spring onions suit the heart of the dry season in the tropics — sow direct from around May to September. They are quick off the mark, germinating in 7 to 14 days, and ready to pull in 60 to 70 days, which makes them one of the faster alliums to reward you. Sow about 10 mm deep and thin to 5 to 10 cm apart, since you are growing for the slim stem rather than a bulb.

In gardens around Broome and Townsville, the cooler dry months give spring onions the mild conditions they prefer without the disease pressure of the wet. Stagger small sowings every few weeks and you will have a steady supply rather than a single glut.

Sowing calendar — tropical zone

Green months are your sowing window: May to September.

Growing notes

Spring onions are a straightforward dry-season pick, and the May to September window keeps them clear of the humidity that rots young allium seedlings during the wet. Because they mature in around two months, you have room to make several sowings across the dry — a late-May start and a July follow-up in the Cairns and Mackay regions will keep the kitchen supplied without any one batch bolting past its best.

They want full sun and a light, free-draining soil that has been worked with compost. Keep the bed evenly moist, as dry spells make the stems tough and can trigger premature flowering. Shallow roots mean they dislike competition, so keep weeds down and thin early to the recommended 5 to 10 cm.

The most common problem is spindly, flopping seedlings that never firm up. This usually traces to sowing too thickly and leaving them crowded — thin promptly and they will stand upright and thicken. You can harvest by pulling whole plants once the stems reach pencil thickness, or snip the green tops and leave the base to regrow for a second, lighter cut. Avoid sowing into the build-up, as the returning humidity from October onward undoes fast, tender growth.

Spring Onion at a glance

Companion planting

Grows well with

Carrot: Scent deters carrot fly

Keep away from

Bean (Bush): Alliums inhibit legume growth

Common questions

When is the best time to sow spring onions in the tropics?

Sow from May to September, through the cooler dry season. Staggering small sowings every few weeks gives a continuous supply.

Can I grow spring onions in Broome?

Yes, the dry-season months from May to September suit them well in Broome. Keep the soil evenly moist and avoid sowing into the humid build-up.

Why are my spring onion seedlings falling over?

They are almost always sown too thickly. Thin them to 5 to 10 cm apart early and the remaining plants will stand up and thicken.

Keep exploring