How to grow zucchini in Australia 🥒

Zucchini needs warm soil (consistently 18°C+), no frost risk, and plenty of sun. They're frost-sensitive at both ends — a single cold night will kill a young plant. Once established, they grow fast, often producing the first fruit within 6–8 weeks of planting.

Zucchini can be grown from seed or seedlings. Seeds germinate readily in warm soil (5–10 days at 20°C+) and zucchini grows so quickly that there's little benefit to starting indoors except in very cool climates.

Spacing: 80–100cm between plants. This is the spacing that surprises people — zucchini plants look small as seedlings but mature plants are huge, with leaves the size of dinner plates. Cramping them reduces airflow (powdery mildew) and limits yield.

Depth: Sow seeds 2cm deep. Plant 2–3 seeds per spot and thin to the strongest seedling after germination. Seedlings go in at the same depth they were growing in the pot.

Soil: Rich, well-drained soil with plenty of compost. Zucchinis are heavy feeders — work in pelleted chicken manure or composted manure before planting. Slightly acidic to neutral pH (6.0–7.0).

Mound planting: In heavy soils or wet climates, plant zucchini on small mounds 15–20cm high to improve drainage at the base of the plant. Wet stems lead to crown rot.

Zucchini is a big plant with big needs — pot growing is possible but demanding.

In-ground is the standard. A single plant occupies roughly a square metre when fully grown, and the unrestricted root run produces the heaviest crops.

Raised beds work very well. The improved drainage and warmer soil suit zucchini's preferences. Allow at least 80cm between plants — the wider spacing also helps the bed cope with the heavy moisture demand of a mature plant.

Pots need to be very large — minimum 50 litres per plant, ideally bigger. Smaller pots stress the plant, reduce yield, and require multiple waterings per day in warm weather. If you only have pot space, look for compact bush varieties (Astia, Black Beauty bush types) rather than standard ones. Even in a large pot, expect a lighter and shorter harvest than an in-ground plant. Feed weekly with liquid fertiliser through the productive period.

Full sun — 6 to 8 hours daily. Zucchini in part shade produces fewer fruit and is more susceptible to powdery mildew.

Water deeply at the base of the plant, not from overhead. Wet leaves invite powdery mildew, which is the single most common problem with zucchini in Australian gardens. Water in the morning rather than evening so any leaf moisture dries before night. Mulch heavily — zucchini's shallow roots dry out quickly.

Harvest zucchini young — at 15–20cm long for standard varieties, smaller for round and patty pan types. Smaller fruit is more tender, better flavoured, and encourages the plant to keep producing. Leaving fruit on the plant to grow into a marrow signals "job done" and slows new flower production dramatically.

Cut fruit with secateurs rather than twisting — zucchini stems break the plant if mishandled. Check plants every 2–3 days during peak production; a small fruit on Monday can be a 40cm marrow by Friday.

The yellow male flowers (long stems, no fruit behind them) are edible and prized — they can be stuffed, battered and fried, or added to pasta. Pick male flowers early in the morning when fully open. Don't pick all the male flowers, though — you still need some for pollination.

Powdery mildew is the most common zucchini problem in almost every Australian climate. It shows up as a white, dusty coating on the leaves, starting on older lower leaves and spreading upward. Once it's heavy on a plant, productivity drops sharply. Prevention is the only reliable approach: space plants well, water at the base rather than from overhead, choose resistant varieties where available, and remove badly affected leaves promptly. A spray of one part milk to nine parts water applied weekly to the leaves can slow it.

Poor pollination causes immature fruit to yellow at the tip and rot, or fruit to not form at all. Usually a sign of low bee activity — common in cool wet weather, in courtyards without flowering plants, or when there are too many male or female flowers and not enough of the other. Hand-pollinate by transferring pollen from a male flower (long stem) to a female flower (the small swelling behind it is the future fruit) with a soft brush.

Squash bug and pumpkin beetle can damage leaves and reduce yield in subtropical and tropical climates. Pick adults off by hand; companion plant with nasturtium as a decoy crop.

Blossom end rot — black, sunken end on fruit — same calcium-related issue as in tomatoes, caused by inconsistent watering. Fix with consistent mulching and watering.

Plant near: Corn (provides shade and supports vining types), beans (fix nitrogen for the heavy-feeding zucchini), nasturtium (decoy crop for squash pests), marigold.

Keep away from: Potatoes (compete heavily and share some diseases), Brassicas (different nutrient needs and growth habits clash).

Black Beauty — The classic dark green zucchini. Productive, reliable, widely available as both seeds and seedlings. Bush habit. Suits most climates.

Cocozelle — An Italian striped variety with excellent flavour. Slightly slower to mature than Black Beauty. Heritage seed suppliers.

Lebanese (light green types) — Lighter green, sometimes pale and speckled. Slightly sweeter, milder flavour than Black Beauty. Productive. Widely available.

Patty Pan (yellow or pale green) — Small, flying-saucer-shaped fruit. Excellent flavour, attractive on the plate. Compact bush habit — the best zucchini for pots.

Costata Romanesco — Italian ribbed variety with rich nutty flavour. Larger plant than Black Beauty. Heritage seed suppliers.

Golden Zucchini — Yellow-fruited variety with mild flavour. More attractive in mixed dishes than green types. Same growing habits as standard zucchini.