When to plant Zucchini in Subtropical Australia

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

Zucchini is sown direct from August through March in the subtropical zone, 15–20 mm deep — drop two or three seeds per station and thin to the strongest. Warm soil brings germination in six to twelve days, and the first fruit can arrive just 50 days after sowing, though slower varieties and cooler starts can stretch to 100. One or two plants at 50–80 cm spacing will bury a Brisbane household in fruit at peak. The real challenge in this climate is rarely getting zucchini growing — it's keeping a plant productive once summer humidity arrives, and that shapes every decision worth making.

Sowing calendar — subtropical zone

Green months are your sowing window: August to March.

Growing notes

Zucchini is frost tender but so fast that the long August–March window is best treated as several short seasons rather than one. Spring sowings crop heavily before the December wet; a February or March sowing grows into autumn's drier air and often stays healthy longest — a favourite trick of gardeners from Coffs Harbour up to the Sunshine Coast. Because plants exhaust themselves and succumb to mildew within a couple of months here, succession sowing every six to eight weeks beats trying to keep one heroic plant alive all season.

Plant into rich, composted soil in full sun and keep water consistent — feast-and-famine watering causes blossom-end rot, where fruit tips blacken and collapse. Always water at the base in the morning; foliage that goes into a humid night wet is an open invitation to disease.

Two failures dominate. Powdery mildew whitens the leaves from mid-summer and is managed rather than cured: airflow, soil-level watering, removing the worst foliage, and having the next sowing already coming on behind. And small fruit that yellows and shrivels from the flower end is a pollination failure, common during stormy weeks when bees stay in — pick a male flower in the morning, dab its pollen into open female flowers, and fruit set resumes almost immediately.

Zucchini at a glance

Companion planting

Grows well with

Nasturtiums: Deters aphids and squash bugs

Marigold: Deters nematodes; attracts pollinators for better fruit set

Nasturtiums: Deters squash bugs and aphids

Common questions

When can I plant zucchini in Brisbane?

Sow direct from August through March. Rather than one sowing, plant a fresh station every six to eight weeks — subtropical zucchini plants burn out quickly, and succession keeps the harvest continuous.

Why do my baby zucchini shrivel and rot at the end?

Fruit yellowing from the flower end is usually failed pollination, common in wet weather when bees stay home — hand-pollinate with a male flower in the morning. If tips blacken on fruit that did set, it's blossom-end rot from uneven watering.

How long does zucchini take to grow?

Seed germinates in around six to twelve days in warm soil, and fruit follows 50–100 days from sowing depending on variety and season.

How do I deal with powdery mildew on zucchini?

You manage it rather than beat it in the subtropics. Water at soil level in the morning, keep full spacing, remove the worst leaves, and have a replacement sowing coming along — old plants will always succumb eventually.

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