When to plant Sweet Corn in Subtropical Australia

Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.

Sow sweet corn direct from January to March and again from August to December, always into warm soil — it is frost tender and won't germinate in the cold. The frost-free subtropical summers around Brisbane and the Gold Coast suit it well, provided you avoid sowing straight into the wettest storm weeks. Seed comes up in about 6 to 12 days, and cobs are ready 80 to 120 days later. Sow 15–25 mm deep and 20–30 cm apart. Crucially, plant corn in a block of short rows rather than one long line, because it is wind-pollinated and needs neighbours close by to fill the cobs.

Sowing calendar — subtropical zone

Green months are your sowing window: August to March.

Growing notes

Corn is one of the few crops that genuinely enjoys the subtropical summer heat, but the timing traps are the wet-season extremes. A very early January sowing can rot or wash out in heavy storms, while a late December sowing risks pollinating in the most humid, still conditions — patchy pollination is what leaves cobs with gappy, half-filled rows. Sowing in blocks and giving the tassels a gentle shake on still mornings helps the pollen reach the silks.

Corn is a hungry, thirsty crop: give it your richest soil, full sun, and deep, regular watering, especially once the tassels and silks appear, because moisture stress at that stage shrivels the kernels. In humid weather watch for rust and the occasional smut, and for corn earworm burrowing into the tip of the cob — a dab of oil on the silks, or simply trimming the affected tip at harvest, usually deals with it.

Because it's frost tender, get spring sowings in only once the soil has warmed, and finish autumn crops before the first cool nights slow ripening. Pick when the silks brown and a squeezed kernel spurts milky, not clear, juice, since corn passes its peak within days and is best harvested promptly.

Sweet Corn at a glance

Companion planting

Grows well with

Bean (Bush): Classic Three Sisters — beans fix nitrogen for corn

Zucchini: Classic Three Sisters variation — zucchini ground cover suppresses weeds

Nasturtiums: Deters aphids; trap crop

Common questions

When can I plant sweet corn in the subtropics?

Sow direct from January to March and again from August to December, into warm soil. Avoid the wettest storm weeks and the cold of midwinter.

Why are my corn cobs only half filled with kernels?

That is poor pollination, common in still, humid weather. Plant corn in a block rather than a single row and shake the tassels on calm mornings to spread the pollen.

How do I know when sweet corn is ready to pick?

Wait until the silks turn brown and dry. Peel back a little husk and press a kernel; if the juice is milky rather than clear, it is ready.

What is the grub burrowing into my corn cobs?

It is usually corn earworm, which enters at the tip. A dab of oil on the silks helps, or simply trim off the damaged tip when you harvest.

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