Corn Growing Guide: from seed to kitchen

How to Grow Sweet Corn (Zea mays)

Corn in the Kitchen – how to tell the types apart

Sweet corn is the juicy, milk-sweet ear you steam, grill or eat raw right in the garden; pick it young before the sugars convert to starch.
Supersweet (sh2) & Sugar-enhanced (se/SE) are simply extra-sweet modern sweet-corn strains—supersweets keep their sweetness longest, sugar-enhanced give the most tender kernels.
Flour or field corn (flint, dent) is harvested fully dry, then ground for polenta, masa, tortillas or cornmeal; the flavour is nutty and starchy.
Popcorn has small, very hard kernels that explode into fluffy white puffs when heated—ideal for healthy snacks.
Ornamental/Indian corn offers rainbow kernels for decoration; when dry it grinds into richly flavoured corn flour.

Seeds per gram: about 4 – 10
Feed requirement: moderate to high

Germination:

Corn will not sprout well in cold ground. Wait until soil temperature is a steady 18 °C (20+ °C is ideal). At that warmth seed emerges in five to ten days; colder soil can cause rots and patchy stands.
In cooler climates start corn on heat beds in order to an early start. Ensure that the cells or pots have good depth as corn puts down down deep roots.
- Transplant the seedlings once the outside soil has warmed and any threat of frost has passed.
- Harden off well and plant out before roots spiral.
- When transplanting Avoid root disturbance.

Sowing and spacing:

Choose a sunny bed with fertile, well-drained soil (pH 6.0-7.0).
Work in plenty of compost or aged manure plus a handful of balanced organic fertiliser per square metre.
Make furrows, back-fill lightly, then sow two-four seeds together 2-4 cm deep.
- Space planting stations 30 cm apart with 90 cm between rows.
- Plant at least two, preferably four, rows side-by-side to create a pollination block; larger blocks give fuller ears.
- When seedlings reach 10 cm, thin each station to the stronger plant. In areas with a shorter summer (eg. Tasmania) use early or mid-season varieties (70–90 days); late-season varieties seldom ripen.

Feeding and watering:

Corn is a grass and loves nitrogen.
Side-dress with blood-and-bone or another high-nitrogen fertiliser when plants are knee-high, then again at tasselling.
Hill a little soil around the stems for support.
Keep moisture even, especially from tassel emergence through grain-fill;
Irregular watering or drought at silking causes missing kernels.
Mulch to conserve water if plants are closer than 30 cm.

Isolation between types:

Supersweet, synergistic and popcorn should be separated from other corn by 200 feet (60 m) or by sowing ten days earlier or later. Cross-pollination lowers sweetness and popping quality.

Problems to watch:

Corn earworm / heliothis – place two drops of mineral oil or a puff of Bacillus thuringiensis (Dipel) on fresh silks to deter the caterpillar.
Poor pollination – thin, patchy ears result from small or windy plantings. Always use block plantings.
Smut, rust, leaf blight – reduce by four-year rotation and removing stalks after harvest.
Birds and rats – slip paper bags over maturing ears or net the block.

Harvest:

Count about 3-4 weeks from full silk emergence. The silks will turn brown and dry; ears feel plump.
Peel back the husk tip and press a kernel: if it squirts milky juice, pick immediately—sweetness declines once picked.
Twist the ear sharply downward to break it free.
Harvest in the morning or evening and chill or cook straight away; supersweets will hold flavour for a day or two longer than old-fashioned varieties.

Storage and use:

Unhusked ears keep three days in a fridge at 2-4 °C.
For winter eating, blanch six minutes, cut kernels, and freeze.
Dried mature ears of flour, flint or ornamental corn store for months and grind into meal;
Popcorn must cure in a dry airy place for several weeks, then store airtight and test-pop until kernels explode fully.

Grow successive sowings or mix early, mid- and late hybrids to enjoy that incomparable garden-fresh crunch for as long as your summer allows