How to grow Zucchini in Australia
Zucchini, or courgette, is one of the most productive summer vegetables: a single bushy plant can give a steady supply of tender fruit from about six to eight weeks after sowing. It needs warm soil, full sun, rich soil and steady water, and bees to carry pollen between its separate male and female flowers. Pick the fruit small and often.
📖 Our full guide: How to Grow Zucchini in Australia
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | August to March | |
| Northern Rivers NSW | September to March | Sow from September to March. Starting in September protects young plants in hinterland frost pockets. |
| Sydney & Coastal NSW | September to February | Start indoors late Aug; direct sow Sept+ when soil warms; avoid frost. |
| Melbourne & Victoria | October to December | Sow direct Oct to Nov (Dec latest). Soil must reach 20°C; don't rush Sept sowing. Frost will kill. |
| Adelaide & SA | September to December | Sow Sep undercover or Oct to Dec direct after frost. Succession sow; plants tire in heatwaves. Hand pollinate early and late in the season. |
| Perth & WA | August to October | Mediterranean: narrow to Aug to Oct sowing. Zucchini set fruit only in warm shoulder seasons; avoid Jan heat stress. |
| Tasmania | October to December | Sow Oct to Dec once soil passes 18C, or start indoors in Sep. Frost kills, but two plants still feed a family. |
| Canberra & ACT | November and December | Frost tender. Sow direct Nov to Dec after the last frost in early November. Crops hard until the first autumn frost. |
| North Queensland | April to August | Dry season Apr to Aug. Townsville plants zucchini from May. Powdery mildew ends wet season plantings fast. |
| Darwin & Top End | April to August | Dry season only Apr to Aug. Darwin zucchini die off once build up humidity arrives in Oct to Nov. |
Not to be confused with: Squash, a close relative grown the same way, including round button or pattypan types. Marrows are simply zucchini left to grow large.
Where to plant
Zucchini need full sun, at least six hours a day, and rich, well-drained soil with compost or aged manure dug in. Working in a couple of handfuls of dolomite lime or gypsum per square metre before planting adds calcium, which helps prevent blossom end rot.
The seed needs warm soil, about 18 to 20°C, to germinate well, and plants are killed by frost. Bushes spread about a metre, and good air flow helps keep powdery mildew at bay.
- South East Queensland: sow from August to March. The Northern Rivers: September to March, starting in September in frost-prone hinterland spots.
- Sydney: sow from September to February, or start seedlings indoors in late August.
- Melbourne: sow from October to December once the soil reaches about 20°C; do not rush a September sowing.
- Adelaide: sow under cover in September or directly from October to December. Sow in succession, as plants tire in heatwaves.
- Perth: sow from August to October. Zucchini set fruit best in the warm shoulder seasons and struggle in January heat.
- Hobart: sow from October to December once the soil passes about 18°C, or start indoors in September. Canberra: sow in November and December after the last frost.
- North Queensland and Darwin: sow in the dry season, from April to August, as powdery mildew and humidity end wet season plantings fast.
How to plant
- Dig in compost or aged manure, plus dolomite lime or gypsum, a couple of weeks before sowing.
- Make low mounds or planting holes about 60 to 80 cm apart.
- Sow three or four seeds about 2 cm deep in each spot. Seedlings appear in one to two weeks.
- Thin to the strongest one or two seedlings per spot.
- Mulch with pea straw or lucerne once the plants are growing, keeping it off the stems.
Watering and feeding
Zucchini are thirsty. Water deeply two or three times a week in warm weather, or give one thorough soaking a week, at the base of the plant rather than over the leaves. Keep the soil consistently moist but not waterlogged. Uneven watering leads to blossom end rot and poorly formed fruit.
Feed with compost or manure before planting and again when flowering starts. A fertiliser higher in potassium once fruit is setting supports cropping better than more nitrogen, which mostly makes leaves.
Pruning and care through the year
- Male flowers, on thin stalks, usually appear first and simply drop. Female flowers have a tiny zucchini behind the petals. Bees carry the pollen; nasturtiums and other flowers nearby help bring them in.
- If small fruit shrivels or rots at the tip, it was not pollinated, or blossom end rot has set in. Hand pollinate in the morning by brushing the pollen from a male flower onto the centre of a female flower with a small paintbrush.
- Remove old, mildewed leaves from the base of the plant to improve air flow.
- Sow a second planting four to six weeks after the first, as plants tire and get mildew by late summer.
Harvesting
Start picking about six to eight weeks after sowing. Pick fruit when it is about 12 to 20 cm long, glossy and tender. Cut it off with a short stalk. Check plants every day or two in summer, as a missed fruit quickly grows into a large, tough marrow and slows new fruit from forming.
The flowers are edible too. Zucchini keep about a week in the fridge.
Growing in pots
Compact bush varieties grow well in a large pot at least 40 cm wide and deep, with a quality potting mix. Water daily in hot weather and feed regularly. Hand pollination may be needed on balconies with few bees.
Using it
Slice zucchini into stir-fries, pasta and salads, grill or roast it, grate it into fritters, muffins and cakes, or stuff and bake larger ones. Zucchini flowers can be stuffed and fried.
Do not eat a zucchini that tastes very bitter. Bitterness comes from natural compounds called cucurbitacins, which can cause stomach upsets in high amounts; throw bitter fruit away.
Saving seed
To save seed, leave one fruit from an open-pollinated variety on the plant until it is large and the skin is hard, then scoop out the seeds, rinse and dry them. Zucchini cross easily with other squash and pumpkins of the same species, so saved seed may not come true unless you hand pollinate and bag the flowers.
Varieties
- Black Beauty
- Golden Zucchini
- Lebanese (Cousa)
- Costata Romanesco
- Tromboncino
Companion planting
Zucchini share the summer bed with corn and beans, and flowers nearby bring in the bees they depend on.
Good companions
- Nasturtium Draws aphids away and brings in pollinating bees.
- Corn A tall summer crop for the same warm, rich bed.
- Beans A summer legume that adds nitrogen and shares the warm season.
- Marigold Bright flowers that bring in pollinators and beneficial insects.
Keep apart
Avoid planting these close to zucchini.
Pests and diseases
Powdery mildew is almost certain by late summer. Leaf-eating ladybirds and aphids are the main pests.
Pests to watch for
- 28-spotted ladybird Orange ladybirds with many black spots and spiny yellow larvae scraping lacy patches on the leaves.
- Aphids Clusters under the leaves; they can spread viruses that mottle the leaves and fruit.
- Slugs Seedlings and young fruit chewed, especially after rain.
- Pumpkin beetle Orange beetles chewing holes in young leaves and flowers.
Diseases to watch for
- Powdery mildew White, powdery patches on the leaves, spreading from mid summer. Water at the base, remove the worst leaves and keep air moving.
- Downy mildew Angular yellow patches on the upper leaf with grey growth underneath in humid weather.
- Blossom end rot Small fruit rotting from the flower end, linked to low calcium and uneven watering. Add dolomite or gypsum before planting and keep moisture steady.
Common questions
Why is my zucchini flowering but not making fruit?
The first flowers are usually male and always drop. Female flowers, with a tiny zucchini behind them, need bees to bring pollen. If there are few bees, hand pollinate in the morning with a small brush or a male flower.
Why are my baby zucchini rotting?
Either the flower was not pollinated, so the fruit shrivels, or it is blossom end rot, linked to low calcium and uneven watering. Work dolomite or gypsum into the soil before planting, keep watering steady, and hand pollinate if needed.
When should I plant zucchini?
In spring and summer once the soil is warm: August to March in South East Queensland, September to February in Sydney, October to December in Melbourne and Hobart, and August to October in Perth. In the tropics, sow in the dry season. Pick your region at the top of the page for the months.
How big should zucchini be when picked?
About 12 to 20 cm long, while the skin is glossy and tender. Bigger fruit gets tough and seedy and slows the plant.
What is the white powder on my zucchini leaves?
Powdery mildew, which almost always appears from mid summer. Water the soil rather than the leaves, remove the worst leaves, give plants space, and sow a second crop to take over.
Is bitter zucchini safe to eat?
No. A strongly bitter zucchini contains high levels of cucurbitacins, which can cause stomach upsets. Throw it away. Normal zucchini taste mild.
How many zucchini plants do I need?
Two or three plants are plenty for most families, as each plant crops heavily. Sow a second batch about a month later for a longer season.
Sources we checked: Yates: How to grow zucchini; Sustainable Gardening Australia: Zucchini; Gardening Australia: Ask it, solve it, small zucchini.