Corn Seeds

How to Grow Sweet Corn (Zea mays)

Corn in the Kitchen – how to tell the types apart

1. 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.
2. 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.
3. Flour or field corn (flint, dent) is harvested fully dry, then ground for polenta, masa, tortillas or cornmeal; the flavour is nutty and starchy.
4. Popcorn has small, very hard kernels that explode into fluffy white puffs when heated—ideal for healthy snacks.
5. 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