Q When do I sow sweetcorn in the UK?
A Sow in April into a deep, 7cm pot to reduce root disturbance later on. Provide a minimum temperature of 15°C to encourage germination and good growth. Harden off the seedlings to plant out after all danger of frost has passed.
Caption: Sow sweetcorn indoors in April
Q What's the difference between tendersweet sweetcorn and supersweet sweetcorn?
A Sweetcorn was bred from the cereal crop maize and is picked when immature, before the sugar-kernels are converted to tasteless starch. Increasing the sugar content, shelf life and suitability for growing in the temperate British climate are all aims of recent breeding programmes, which have resulted in several types of sweetcorn. Standard varieties have an old-fashioned corn flavour, but the sugars turn to starch as soon as they are picked. Sugary enhanced (SE) types have thin skins on the kernels and a good flavour, but they are not very sweet. Supersweet (SH2) types have high sugar with a good shelf-life. Tendersweet, the most recent innovation, combines thin skins with good sweetness and taste.
Q Where should I plant sweetcorn?
A Once the danger of frost has passed in your area from mid-May to early June, depending where you live, choose a sheltered site in full sun, and dig in garden compost or soil improver. Plant in blocks of at least 12 plants to ensure good wind-pollination, but keep different varieties separate to avoid crosspollination, which can affect the quality of the cobs. Spacing plants at 35cm generally gives one good cob per plant. Plant further apart (45cm) if you want to try for a smaller second cob, too.
Caption: Plant sweetcorn in blocks to help pollination
Q How do I care for my sweetcorn plants?
A Water when the cobs start to form and the silks appear on the ears of corn. At this time it is also a good idea to shake the sweetcorn stems on a still evening. This ensures that pollen released by the male flowers at the top of the plant lands on all the female silks in the cobs below and helps to ensure that every kernel develops.
Caption: Shake sweetcorn to help pollination
Q Which pests and diseases attack sweetcorn?
A Sweetcorn can suffer from smut – a disease that causes cobs to erupt with black mould. It's not common, but destroy affected plants and grow your corn in a different spot next year.
Sweet-toothed critters, such as rats, squirrels and crows, love ripe cobs.
Badgers and deer are also excellent at telling when cobs are ripe, so we had to protect our trial crops with an electric fence.
Q How do I tell when sweetcorn is ripe?
A The cobs should be ripe when all the silks are brown and shrivelled. Peel back the sheath and the kernels should be plump and yellow. Push your fingernail into a kernel – the liquid that is released from it should be milky when the cob is ready for you to eat.
Q How quickly does sweetcorn lose its sweetness?
A You may have heard that sweetcorn loses its sweet taste rapidly after it's picked because its sugars turn to tasteless starch. We wanted to find out whether it's the variety that you grow, or how quickly you eat it, that has the biggest effect on how sweet it is. So we used a Brix test, which measures the Day 0 Day 1 Day 4 Day 7 sugar content of vegetables, to find out how quickly the sugar level drops in refrigerated corn.
We found the variety 'Swift' went from a Brix score of 17.2 to 16 over a period of seven days. Our results suggest it’s more important to choose a sweet variety such as 'Swift', than to eat it quickly to get the sweetest results. A Brix score of 10-18 is considered average to good for sweetness in sweetcorn.