When To Sow: April (indoors); May (direct seed) Harvest: August-October
Germination: 2-25 (11 average) Full Sun
Plant in sheltered spot where the soil is both rich, well-drained, and has a pH between 6.5 – 7.5. Make sure the crop won’t shade out other sun-loving plants (the plants grow between 180-220cm tall.) Like most other corns wind pollinated and best planted in large blocks – not in rows. (For best results, a minimum block of 4x4 plants is recommended.) Sweet corn tends to have very shallow roots that need protection both from wind and water loss in the soil.
Although corn generally doesn’t like to be transplanted, if care is taken not to disturb the roots it can be started indoors in the spring (generally April). Most folks prefer to sow directly outside in May.
Starting Indoors: Sow in cells or 3-inch pots filled with good, free-draining compost. The compost should be moist, but not waterlogged. Saturated compost will not only be cold, but also can reduce the amount of oxygen your seeds need to germinate. Sow 2 seeds per pot or module.
Once the starts are 2cm (1”) tall, thin to the strongest seedling. When the soil outside has warmed and all chance of frost has passed, harden plants off gradually and plant in a block with 25 to 30cm (10-12”) between plants and 60cm (24”) between rows.
Direct Seed: Sow directly in a sheltered, well-fertilised plot when the soil has warmed and all chance of frost has passed. Plant in a block to ensure maximum pollination (minimum 4x4 plants). Space plants 25 to 30cm (10 to 12in), with 60cm (24in) between rows.
Note: Sweet corn seed does not germinate below 10°C (50°F), so make sure the soil has adequately warmed before planting. It also needs a good summer to produce at its best.
Sweet corn likes a lot of water, so make sure you water regularly, especially once you see cobs starting to form. (If you see the leaves curling when the cobs begin to swell, this a sign your plants need more water.) Apply a nitrogen fertiliser once the plants are about 20cm (8”) tall and again when they start producing tassels.
Keep the area between the plants free of weeds, either by mulching, inter-planting (beans and squash are a great option), or by light hoeing.
Test for ripeness when the silky tassels have turned a chocolate brown. Peel back the sheath and squeeze a grain between thumbnail and fingernail: if a watery liquid squirts out, it’s not ready yet. If the liquid is creamy, the cob is ready. If paste-like, the cob is over-mature.
To harvest, twist the ripe cobs from the stem. Make sure you eat them soon after harvesting—the cobs rapidly lose their flavour after picking.