How to grow Sweet Corn in Australia
Home-grown sweet corn picked minutes before cooking is far sweeter than anything you can buy. It is a warm-season crop that needs rich, warm soil, plenty of water and, above all, planting in a block rather than a single row, because the cobs are pollinated by wind. Grow one type at a time so the cobs stay sweet.
📖 Our full guide: How Long Does Corn Take to Grow? Sweet Corn in Australia
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | August to February | |
| Northern Rivers NSW | September to February | Sow from September to February. Inland, make sure the frost risk has passed, as corn seedlings are cut down by a late frost. |
| Sydney & Coastal NSW | September to January | Spring planting (Sept+); shorter season than tropical baseline. |
| Melbourne & Victoria | October to December | Sow direct Oct to Dec once soil 20°C+. Frost-tender; Feb to Apr harvest before autumn frost. No winter sow. |
| Adelaide & SA | September to January | Sep starts undercover only. Direct sow Oct to Jan into warm soil in blocks for pollination. Water deeply through summer. |
| Perth & WA | August and September | Mediterranean: sow Aug to Sept only. Sweet corn fails in extreme summer heat; prefers spring-early summer establishment. |
| Tasmania | October to December | Sow Oct to Dec in the warmest spot. Grow early varieties only, because cool summers slow ripening. Block plant for pollination. |
| Canberra & ACT | November and December | Sow Nov to Dec into warm soil after the last frost in early November. Choose early maturing varieties; plant in blocks for pollination. |
| North Queensland | April to November | Dry season crop in NQ. Bowen and the Burdekin plant sweet corn Apr to Nov. Avoid the Dec to Mar monsoon peak. |
| Darwin & Top End | March to August | Dry season main window Mar to Aug per NT growers. A November sowing for a wet season crop is possible but risky. |
Where to plant
Grow sweet corn in full sun in rich, well-drained soil with plenty of compost and manure dug in; it is a hungry crop. Shelter from strong wind helps, as tall plants blow over.
Plant in a block of at least four short rows rather than one long row. Corn is wind pollinated: pollen falls from the tassels at the top onto the silks of the cobs below, and in a block every plant has neighbours whichever way the wind blows. Poor pollination gives cobs with gaps.
- Sydney and Adelaide: sow from September to January into warm soil, under cover for September starts in Adelaide.
- Melbourne and Hobart: sow direct from October to December once the soil reaches about 20°C. In Hobart choose early varieties for the warmest spot.
- Canberra: sow in November and December after the last frost, choosing early-maturing varieties.
- Perth: sow in August and September so plants establish before the extreme summer heat.
- South East Queensland and the Northern Rivers: sow from August or September through to February.
- North Queensland: a dry-season crop, sown from April to November. Darwin: sow from March to August in the dry season.
Choosing a variety
- Supersweet hybrids such as Honey Sweet stay sweet for longer after picking, but must be grown away from other types, or cross-pollination makes the kernels starchy.
- Heirloom and open-pollinated types such as True Gold can be saved from seed.
- Plant one variety at a time, or stagger sowings so different types do not flower together.
- Popcorn and ornamental corns must also be kept well away from sweet corn.
How to plant
- Wait for the soil to warm; seed rots in cold, wet soil.
- Sow seed about 3 cm deep in a block of short rows, 30 to 40 cm apart each way, two seeds per spot.
- Thin to the strongest seedling once they are up.
- Sow another block three or four weeks later for a longer harvest.
Watering and feeding
Water deeply and regularly, and never let the soil dry out once the tassels and silks appear; that is when water stress costs you the crop. Mulch well.
Feed with a nitrogen-rich fertiliser or side dressing of manure when plants are knee high and again as the tassels appear.
Pruning and care through the year
- Hill soil up around the base of the stems as plants grow, to support them against wind.
- If pollination has been poor in the past, gently shake the stems or tap the tassels over the silks on a still morning.
Harvesting
Cobs are ready about three weeks after the silks appear. Check when the silks have turned brown and shrivelled and the cob feels full: peel back a little husk and press a kernel with your fingernail. Milky juice means ready; clear juice means not yet; thick, doughy paste means it is past its best.
Twist the cob down and off the stalk. Cook or refrigerate it straight away, as the sugar starts turning to starch soon after picking, especially in older varieties.
Saving seed
Save seed only from open-pollinated varieties grown well away from any other corn. Leave the best cobs on the plant until the husks are dry and the kernels hard, then dry them further indoors and rub off the kernels. Seed from hybrid varieties does not come true.
Companion planting
Sweet corn is one of the traditional three sisters: corn, beans and squash grown together, with beans using the corn as support and adding nitrogen, and pumpkins shading the soil.
Good companions
- Beans Climbing beans can use corn stalks as support, and beans add nitrogen to the soil.
- Pumpkin A sprawling crop that shades the soil between the corn and holds moisture in.
- Zucchini Another summer squash for the shaded ground under the corn.
- Cucumber A summer crop that likes the same warm, rich soil and steady water.
Keep apart
Avoid planting these close to sweet corn.
- Tomato Shares the same caterpillar pest, the corn earworm or tomato grub, so planting them together can build up numbers.
Pests and diseases
Caterpillars of the corn earworm moth, also called heliothis or tomato grub, are the main pest. They feed in the tips of the cobs.
Pests to watch for
- Corn earworm Caterpillars and droppings at the tip of the cob under the husk, with chewed kernels. Cut off damaged tips; the rest is fine to eat.
- Birds Husks torn open and kernels eaten as cobs ripen.
Diseases to watch for
- Rust Small, raised, rusty brown pustules on the leaves, worst in humid weather.
- Smut Large, swollen grey galls on cobs or tassels that burst into black powder. Remove and bin galls before they burst.
- Northern corn leaf blight Long, cigar-shaped grey-green to tan lesions on the leaves in warm, humid weather.
Common questions
Why are my corn cobs only half full?
Poor pollination. Corn is wind pollinated, so plant it in a block of short rows rather than a single row, and keep the soil moist when the silks appear. Hot, dry winds at flowering also reduce pollination.
How do I know when sweet corn is ready to pick?
About three weeks after the silks appear, when they have turned brown and shrivelled. Peel back a little husk and press a kernel: milky juice means it is ready.
Why isn't my corn sweet?
It may have been picked too late, left too long before cooking, or cross-pollinated with another type of corn nearby. Grow one variety at a time, especially supersweet types, and cook the cobs soon after picking.
How far apart should sweet corn be planted?
About 30 to 40 cm apart each way, in a block of at least four short rows.
When should I plant sweet corn?
Into warm soil after frost has passed: from spring into summer in the south, from late winter in the subtropics, and in the dry season in the tropics. Pick your region at the top of the page for the months.
What are the grubs in the tip of my corn?
Corn earworm caterpillars, also called heliothis or tomato grub. They usually only damage the tip; cut that off and eat the rest.
Can I grow sweet corn and popcorn together?
Not side by side. They cross-pollinate, which spoils both. Grow them well apart, or time sowings so they flower at different times.
Sources we checked: Gardening Australia: Growing Corn; Gardening Australia: Sweet corn plant finder; Sustainable Gardening Australia: Growing sweet corn; ABC Organic Gardener: How to grow sweet corn; RHS: How to grow sweetcorn.