The Best Guide To Growing Corn From Seed

Corn rewards patience with sunshine on a stick. This guide shows how to grow corn in NZ from seed to harvest, including when to plant corn NZ, choosing the right sweetcorn, how to sow corn seeds, growing sweetcorn in pots or grow bags, watering and fertilising corn plants, cross-pollination corn basics, corn companion plants including Three Sisters planting and corn, common corn growing problems NZ, how does corn grow steps, plus clear signs for how to tell when corn is ready to pick. If you want to buy corn seeds NZ from Trusted Seeds NZ and seed suppliers NZ, Kings Seeds has you covered.

Check out our Top Tips Reel on corn here.

When to Plant Corn in NZ

Warmth and Timing:

  - Warmth unlocks everything; sow when soil temperature is steady at 18 to 20 °C and frost risk has passed.

  - Northland and warm coastal areas in Zone 1 & 2: start sowing in late October.

  - Most regions: sow throughout November.

  - Cooler districts, Zone 3 & 4: wait until late November.

  - Late sowings can be effective if autumn remains mild.

Planting Corn:

  - Corn relies on wind pollination.

  - Plant in blocks of short rows instead of one long line to facilitate pollen drifting across silks.

  - Stagger sowings every two weeks to spread the harvest while the season stays warm.

Protection from Cold:

  - Cold snaps can slow growth.

  - Use cloches or a sheltered bed if spring weather is unpredictable.

Choosing Corn Varieties

Match variety to your place and plans.

• Compact plants suit growing sweetcorn in pots or growing corn in grow bags.

• Field or flint corn suits drying, meal or stock feed.

• If fresh cobs are the goal, pick sweet types.

• Popcorn varieties are also an excellent choice for drying and using to create your own fresh homemade popcorn.

• Look for disease resistance where rust appears regularly.

• Open-pollinated types allow seed saving. Hybrids often bring stronger, uniform, reliable cobs.

• For mixed gardens, consider pairing with beans or pumpkins in the Three Sisters planting method, along with corn.

When you are ready to buy corn seeds NZ or wondering where to buy sweetcorn seed online, head to Kings Seeds.

Corn Sowing Methods

Corn moves best when undisturbed, so direct sowing is the usual path once the soil is warm.

• Sow directly in well-prepped garden beds.

• Place the seed 2-3cm deep. Space plants 20cm apart with 60cm between rows. Sow two seeds per station then thin to the strongest seedling.

• Plant in blocks, not single rows.

• Arrange four or more short rows in a rectangle to improve pollination.

• Pots and grow bags can also be used for small-space gardening; fill with a quality mix plus compost, and keep moisture steady. Containers and pots can dry out faster and stress the plant.

• Protected seed and seedlings from pests such as birds, slugs and snails.

• In cooler spots, start in wool pots for a brief head start and to avoid transplant shock.

Water after sowing and keep the top few centimetres moist until the emergence of the seedling. Birds love freshly sown beds, so netting can save the day.

Soil Prep & Maintenance for Corn Seedlings

Prepare the ground to ensure a consistent food and water supply.

• Add mature compost before sowing and mix it through the top 20cm.

• Aim for a sunny site with six or more hours of light. A wind shelter helps tall stems stand straight.

• Check drainage. Raised beds help heavier soils warm faster and drain better.

• Keep a mulch blanket once seedlings reach 15cm to lock in moisture and suppress weeds.

• Side dress with nitrogen as plants reach knee height and again at tassel time. Liquid feeds during dry spells keep growth even.

• Water deeply rather than little and often. Dry roots during silk formation lead to patchy ears.

Weed early. Corn roots sit near the surface, so careful weeding avoids damage.

How to Grow Corn: Step by Step

1. Choose a variety that fits your season and space.

2. Prepare soil with compost, remove weeds, set up wind shelter if needed.

3. Sow in warm soil at the correct depth and spacing. Use block layout for pollination.

4. Thin to one strong seedling per station. Keep moisture steady as roots spread.

5. Feed at knee height. Mulch to hold water. Stake in windy sites.

6. Encourage pollination by gently shaking stalks at midday over two or three days as tassels shed pollen. For small beds or pots, brush pollen from tassels onto fresh silks to fill every kernel. This simple step solves many of the "Why did my corn not form cobs?" moments.

7. Watch for corn pests and problems. Aphids gather on soft growth. Caterpillars can chew silks and tips. Rats & birds peck at maturing ears. Inspect often and act early with nets, hand removal, water sprays or approved controls suited to food crops. Good airflow and crop rotation help with rust and leaf spots.

8. Mind spacing. How far apart to plant corn matters. Too tight gives small plants. Too wide a distance reduces pollen contact. Stay close to recommended gaps.

9. Consider companions. The classic Three Sisters planting involves beans that use corn to climb, while feeding the soil and pumpkin to shade the soil. A living team fills the bed, limits weeds and supports soil life.

10. Harvest at peak sweetness. See the next section for how to tell corn is ready, so cobs reach the kitchen at their sugary best.

Growing Corn in Tight Places

Pots and grow bags work when you keep feeding and watering regular. Place containers together so pollen can move to each plant. A sunny wall adds warmth. 

Cross-pollination Corn Notes

Planting different types side by side can mix traits because pollen travels on wind. If saving seed or keeping a special type pure, separate by distance or time.

How to Tell Corn is Ready for Harvest

Sweetness peaks fast. Use all your senses and answer the key question many ask "How do I know when my corn is ready?"

• Tassels at the ear tips turn chocolate brown and dry off.

• Ears feel firm and full right to the tip when squeezed.

• A kernel punctured with a fingernail releases milky juice. Clear liquid signals a little early. Doughy texture signals late.

• Husks lose their lush green and start to pale slightly.

Pick in the cool of the morning. Cook soon after harvest because sugars change quickly. If several sowings were made, check each planting every day during peak time.

Frequently Asked Questions

Q: What month to plant corn in NZ?

A: Most gardens sow corn seed from late October through November once soil stays above 20°C. Cooler areas may wait until late November. Warm districts can start earlier if frost risk has passed.

Q: How long does corn take to grow?

A: From sowing to harvest takes about 80 to 100 days depending on variety, warmth and feeding.

Q: How far apart to plant corn?

A: Space plants 20cm apart in blocks with 60cm between rows. This layout boosts wind pollination and gives full ears.

Q: Can I grow sweetcorn in pots or grow bags?

A: Yes. Use a wide and deep container with rich mix and steady watering. Group containers so pollen moves between plants.

Q: How to hand pollinate corn?

A: On a dry day while tassels shed pollen, tap pollen onto a clean spoon or card then dust it over fresh silks. Repeat for two or three days to fill kernels evenly.

Q: Why did my plants make small or patchy cobs?

A: Often spacing was too wide for good pollen contact or plants dried out during silk formation. Plant in blocks, water deeply, feed at knee height and during tassel stage.

Q: What not to plant next to corn?

A: Avoid onions or potatoes right beside corn because they compete heavily. Beans and pumpkins partner well in the Three Sisters planting method.

Q: Can you grow different types of corn next to each other?

A: You can, but cross-pollination corn will mix genetics and can ruin crops. If you plan to save seed or keep a specific trait, isolate by distance or sow weeks apart.

Q: How to tell when corn is ready to pick?

A: Look for dry brown tassels at ear tips, full firm ears and milky juice in kernels. Pick promptly for best sweetness.

Q: How to grow field corn?

A: Prepare fertile ground, sow in blocks, feed well. Harvest when ears dry on the plant, then cure thoroughly before storage.

Grow Corn This Season

Kings Seeds is a New Zealand owned family business with over 40 years supplying quality seed and advice to gardeners and growers nationwide. We are gardeners too, and every batch goes through strict germination testing, so you get the Best Seeds in NZ from trusted seed suppliers you can rely on.

Ready to sow, nurture and nourish your own patch. Explore our sweetcorn range and buy corn seed today so those golden cobs can shine on your table this season.