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Sweetcorn or maize, (Latin name – Zea mays) does not always grow well in vegetable
gardens in the north of the UK. Sweetcorn should receive at least eight hours of sunlight a day, so it needs a sunny site in the vegetable garden. Cold winds will slow growth, as sweetcorn is originally a sub-tropical plant, and likes to be warm.
Sunlight, warmth & water are essential for growing sweetcorn (also known as corn on the cob) successfully in the vegetable garden. Sweetcorn must keep growing, without any interruptions.
- Sow sweetcorn seeds in the greenhouse, or on the windowsill, 4cm (1½ inches) deep in 7.5cm (3 inch) pots of free draining compost. Place in a propagator or seal container inside a polythene bag and place at 18-20C (64-68F) until after germination which takes 7 to 10 days. Do not exclude light as this helps germination.
- Plant out into the garden when the weather is set to be very warm and all chances of frost have gone, 45cm (18in) apart in blocks. This is usually early June. Sweetcorn can be sown outside in the middle of May when the soil temperature has reached 12C – but it leaves a very short growing season. Sow 2 seeds 5cm (2 inches) deep, 23cm (9 inches) apart, and in rows 45cm (18 inches) apart. Thin out to the strongest seedling.
- Site should be warm & light, with at least eight hours of sunlight a day, & protected from the wind. Winds will cool the area down and blow the sweetcorn over when it is tall.
- Soil for sweetcorn should be light and well drained. Unless the vegetable garden is very light, it is best to dig a trench about two feet deep. There must be no compaction at the bottom of the trench. Fill the trench almost to the top with compost. Add some vermiculite to lighten the soil and help with drainage. Dig in a little farm yard manure. Cover with a layer of sand, and mix this in to lighten the soil. The sweetcorn roots will be able to grow freely in this light, free draining trench.
- Nutrition – Sweetcorn uses a lot of potash, which it will get from the compost. The corn needs a little nitrogen which will come from the farm yard manure around the
- Plant sweetcorn in blocks, not rows, as they are pollinated by wind (not insects) so if they are blocks there’s a much better chance of pollination occurring . Also the plants will support each other in blocks & are less likely to be blown over & damaged by wind.
- Watering sweet corn is vital to produce full, healthy ears. Once the tassels appear, the sweetcorn needs at least one inch of water per week.
It is important that the soil does not dry out between watering, so in a dry period the corn needs more frequent watering. The corn will not be able to fill out if it does not receive sufficient water and, as a result, the seeds will be small and shrivelled.
- Keep weeds down by hoeing regularly when weeds are small
- Harvest when the liquid of the grains in the cob is thin and creamy. Once the tassels have turned brown, test for ripeness by peeling back the outer husks and pushing your fingernail into the cob. The cob is ready to pick if a milky solution comes out, but if the liquid is clear, leave it a little longer.
- Sweetcorn varieties grown in the vegetable garden are of the flint type – shaped like a tooth. It is important to choose an early variety if it is growing in the UK, where the summers are short. There are some new varieties available which are very early. Northern Extra Sweet F1 Hybrid is suitable for north UK.
- Mini sweetcorn are planted out 4-5in apart in rows 8in apart, in blocks. Harvest the tiny cobs when the silks first show above the husks.
- Containers or troughs can produce large cobs, if the containers are deep enough.
The tubs should be at least 18inches deep, to allow the sweetcorn roots
to develop. The troughs must have holes at the bottom, to allow water to
drain away.A 5 inch layer of Farm Yard Manure, at the bottom of the trough, gives
the roots something to go down into. Cover the manure with compost.
Vermiculite and sand can be mixed with the compost, so that the trough
is filled with a light, free draining growing medium.The advantage of growing sweetcorn in containers is that the pot can
often be tucked into a sheltered suntrap.
Sweetcorn (corn on the cob) can be grown successfully in the vegetable garden, remembering that it is a sub-tropical plant which needs water, warmth and light.