Zea Mays was first domesticated in Central America spreading north and south from there. The Spanish were the first Europeans to see this crop and the rest is history.

Sweet corn is one of the easiest crops to grow given the right conditions. The time to harvest is no greater than many other common garden crops, but still people will insist on buying “fresh” corn from supermarkets or similar outlets.

sweetcorn- growth and storage

Above: Sweet Corn

Growing Sweet Corn - Requirements

  • Sweet Corn is a gross feeder, requires lots of water, and an ambient temperature of at least 20 degrees celsius.
  • Prepare the soil with compost, pelletised Fowl manure, and animal manure if available. Try to find pelletised manure that has added Potassium Sulphate. Potassium improves the quality of cobs. Plain manures are low in potassium.
  • Water the corn to field capacity as often as it needs it. This varies with soil type, climate and water availability. Water quality will have some effect if high in salts. There's no controlling the temperature except by using local knowledge to judge the best time to plant.

sweetcorn- growth and storage immature cobs

Above: Cobs are well formed but immature

Planting & Growth

Having selected the corn seed you wish to plant, then it is time to plant it, at least in the spring/summer. I see some references suggest planting as close as 15cm, then thinning to 30cm. If the seed is fresh, then a high percentage of seed will germinate, do this and you’ve lost half the crop before you start.

I plant my seed up to 25mm deep, then 30 – 40 cm. apart, in rows that form blocks. It is important to plant a lot at once, in blocks to aid pollination. The pollen forms on the tassels at the top of the plant and drifts down onto the silk of the forming cob. You can aid this by gently shaking the stalks or even taking it from the tassels by hand and placing it on the silk. I can’t really say whether this works, but it makes me feel I’m doing something to improve the crop.

sweetcorn- growth and storage maturing plants

Above: Maturing plants 180- 200cm


When is it best to harvest sweet corn? Tomatoes turn red, pumpkin plants die off. What do I look for in a corn stalk? Volumes have been written about this, but a picture is worth a thousand words.

sweetcorn- growth and storage - immature cob

Above:  Immature cob

The cob in the picture above is almost ready. Feel the cob gently through the husk and you’ll know if it is filled out. But the Silk is still green and the cob almost upright. You’ll see the cob on the lower left is missing the silk. It has been clipped off evenly, which suggests a locust, but also may be caterpillar which will be inside gorging on sweet corn. Luckily, only the outside silk was eaten, but such cobs should be picked as early as possible, to save what is left.

sweetcorn- growth and storage - mature cob

Above: Mature cob

The cob in above is mature. It is obviously well filled out, its silk is dry and brown and it is standing out at an angle of approximately 30 degrees from the stalk. There is only one thing left to do, pick it.

sweet corn harvest

Above left: Fresh picked corn, Above right: Filled cobs

Picking corn cobs is relatively simple; find the most mature ears, grasp firmly, push down and twist at the same time and it will break away cleanly.

Then pull away the husk to expose the cob. The silk inside is still green only the outside part turns brown. Strip the husk completely and throw into the compost bin.

sweetcorn- growth and storage

Above: The result


Before you attempt any storage, taste what you have produced, no point keeping anything you are not going to use. This is a worthwhile crop; 8g of seed produced 65 cobs, just over 14kg in weight.

Many sources will insist that blanching is necessary to preserve the colour and flavour of corn on the cob. Dip the cobs in near boiling water for 8 minutes, cool quickly and freeze. It’s the cooling quickly that presents the problem. If it is not done properly retained heat will continue to cook the cob, long afterwards. Good luck with that.
Should I bother? Well I certainly don’t. I pack my produce within 30 minutes of picking into the freezer. It won’t last until the next season, it’ll be eaten. It’s sweet and tender to the last cob.

sweetcorn- growth and storage - packed and frozen

Above: Packed and frozen


A small tag inside a bag of any frozen produce helps keep track of the date it was frozen.

Major Pests & Diseases

Caterpillars, of any type are harmful to your crop, Helicoverpa Zea, the corn earworm, tomato worm and many other names. Their adult form is a moth. If you have birds in your garden they will eat moths and caterpillars. Also you may notice wasps of various types around your crop. They are busy hunting caterpillars.

Grasshoppers and locusts, the latter are more destructive than the former. An inspection of your crop morning and afternoon will turn up some, show no mercy.

Mice, if they live outside, they’re fine by me. They will however dig seed out the ground and eat it. If you find that your seed is not germinating, check to if it is still there. Look for evidence of digging. It only takes one. Lay a very fine mesh over the bed until germination.

Sweet Corn suffers from a large number of bacterial and fungal diseases, rarely seen in the home garden. Keep plants growing strongly and there should be no problems.

Happy gardening,
Gregg Jacobson.

Photographs by Gregg Jacobson