How to Grow Sweetcorn
Nothing beats the taste of freshly picked sweetcorn straight from the garden. It’s a New Zealand summertime favourite and surprisingly easy to grow if you give it plenty of sun, warmth and space. Read our expert tips to help you grow juicy, delicious corn.
Selecting the Right Variety
Consider the sweetness, intended use, kernel colour, climate and harvesting time when selecting what you want to plant.
Varieties to grow:
- Golden Sweet F1: modern golden-kernel super sweet, great for summer harvests in NZ
- Bicolour F1: juicy kernels in two-tone colour, fun and tasty for the family
- Honey & Pearl: two-toned Kiwi classic with proven home-garden performance
- Painted Mountain: multi-coloured ear with a novelty twist (great for the garden and curious eaters)
- Extra Sweet hybrids: if you’re after maximum sweetness and long flavour retention, look for modern hybrids in this category
Try something new: our friends at Kings Seeds even have rainbow varieties for a bit of colour and fun in the patch.
Ideal Planting Conditions
For good pollination, plant corn close together in a block instead of one long row – this helps the pollen spread and ensures full cobs. It also supports the plants as they grow.
- Many people think corn can grow anywhere; but it needs a rich, friable (crumbly) soil.
- In early spring, begin preparing the location you want to grow your sweet corn by adding ample amounts of Garden Time Compost to the existing soil.
- Continue adding compost until you are ready to sow seed or plant young seedlings.
Prime Planting Time
- Sow seed directly into the garden from October through till December – in cooler regions it is best to wait until early November.
- Sweetcorn takes around 90-100 days to mature from sowing so make sure the soil is warm enough and allow plenty of time for the cobs to ripen before the cooler weather arrives.
- To extend your harvest, sow small amounts of seed in successive weeks throughout late spring and early summer. This will stagger maturity and stop all your corn being ready at once, giving you fresh cobs for longer.
Planting in the Garden
- Mix in plenty of Daltons Garden Time Compost and Garden or Vegetable Mix prior to planting.
- Always plant corn in blocks of 3-4 rows for better pollination.
- Sow seeds about 2-3cm deep and spaced 20-25cm apart.
- Apply a layer of Daltons Premium Mulch & Grow and water in well.
Fertilising
Sweetcorn is a heavy feeder, which means it quickly uses up soil nutrients and needs regular fertilising throughout the growing season - poor crops are almost always due to low soil nutrition.
- Feed plants regularly with Daltons Vege & Herb Fertiliser, watering it in well each time.
- Liquid feedings of Daltons Seafeed every 7–10 days will further support strong, healthy growth and large, juicy cobs.
Watering
- As plants develop, water them deeply up to twice a week until the cobs mature.
- Regularly apply mulch as this aids water retention by hindering water evaporation, keeping the moisture in the soil.
Harvesting
- Sweetcorn is ready to be picked when the silks at the top of the cob tun dry and brown.
- You can check their readiness by peeling back the husk slightly and piercing a kernel with your fingernails – if milky liquid comes out it is ready to pick.
Daltons Top Tip: for the best flavour – harvest in the evening and cook straight away. Corn is at its absolute best within hours of picking.
General Care and Maintenance
- Crop rotation is crucial when growing corn. Avoid planting it in the same spot each year, as it depletes the soil of nutrients more than other summer vegetable crops.
- Consider growing cover crops after harvesting to improve soil.
Pests & Diseases
- Corn earworm caterpillars can burrow into cobs – inspect regularly and remove by hand – throw them to your chickens if you have them, they love to eat them!
- Aphids can be found on leaves and tassels – wash off with water and use safe sprays if necessary.
- Rust and fungal disease can occur from overwatering and inadequate airflow.
Gardening Terms Explained
- Heavy Feeder: A plant that needs lots of nutrients to grow well.
- Side-dressing: Adding fertiliser beside plants (rather than over the top).
- Pollination: The transfer of pollen from the male tassels at the top of the corn plant to the female silks on the cobs.
- Successive Sowing: Planting small batches of seed every few weeks rather than all at once. This spreads out the harvest, so your crops don’t all mature at the same time.
- Friable Soil: Soil that crumbles easily when handled - it’s soft, well-aerated, and ideal for plant roots to grow through.
