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All you need to know

Sweet Corn

Nothing beats the super-sweetness of freshly-picked corn on the cob, and thanks to the increasing range of varieties suited to the British climate they can be grown just about anywhere.

Sweet corn has something of an unfair reputation for being difficult to grow in this country, but you only have to look at farmers’ fields in late summer to see great swathes of the stuff gently swaying in the breeze. Over the last few decades considerable effort has gone into breeding varieties suitable for home growing that are reliable and will crop in the face of a variety of weather conditions. The result is a richly-deserved renewed interest in growing sweet corn. Once you’ve tried it for yourself and realise how easy it is to cultivate, you’ll likely grow it every year! Shop-bought cobs aren’t a patch on home-grown corn – it really has to be tasted to be believed.

The best sweet corns for growing in the garden are the early or mid-season types. Late varieties will produce a crop in milder parts of the country and are very useful in extending the picking period. In other areas, however, you’ll need to opt for earlier types that will grow quickly and won’t disappoint. Sweet corn is generally wind-pollinated, so it needs to be grown in blocks rather than long rows. Miniature varieties such as ‘Minipop’, however, are picked before the female tassels are fertilised. They can therefore be planted in rows and make excellent shelter belts. Traditional sweet corn stalks will produce between one and two cobs per plant, so use this rule of thumb as the basis for planning how many to grow to sate your appetite.

Ideally the ground will be moisture retentive but not allowed to ever become saturated during wet spells. Work in plenty of rotted manure or compost the autumn or winter before planting so that it has plenty of time to be incorporated - aim for a bucket load per square metre. This extra organic matter will improve the structure of the soil, increase the level of nutrients available to the plants and help the ground to warm up quicker in the spring (sweet corn needs plenty of heat). About a week before planting out or sowing the seeds add a good scattering of organic fertiliser pellets, such as concentrated chicken manure, and rake the soil level. Don’t worry too much if you missed the opportunity to prepare the plot last autumn, as you should still get good results by digging over the soil this spring and incorporating compost now.

Plenty of sunshine is crucial if the plants are to grow strongly, so aim for a south-facing aspect that will be warm and sheltered. This is probably even more vital to the success of a crop than the soil conditions. Shelter is important as the tall plants will be liable to excessively bend and flex in exposed locations. If you want to sow seeds directly outside in May, then position cloches over the future rows two weeks before the sowing date to warm the soil and speed germination.

Seedlings are not tolerant of frost, which means the earliest you can sow outside directly is mid May. In southern counties you may get away without using cloches or horticultural fleece to warm the soil beforehand, although these will certainly help to make the conditions better. Wait until the soil has dried out slightly before sowing and then set out your seeds in pairs at a depth of 2cm. Space each sowing hole 45cm apart within the row and each row 60cm apart. To maximise the chances of successful wind pollination, plan for a near-square arrangement (see ‘Blowing in the wind’ box).

Alternatively, sow indoors or in a greenhouse from April onwards. Use a quality seed or multipurpose compost. Seedlings hate having their roots disturbed, so sow directly into 7cm fibre pots or home-made versions created using loo roll centres. This will give a good depth of compost for the roots to grow into. They’ll also be able to burst through these make-shift containers, which can be planted whole to reduce the chances of unsettling the roots. Place the seeds 2cm deep in the pots and maintain a minimum temperature of 16°C while they germinate. Once they are through, grow them on at temperatures of no less than 10°C. This shouldn’t be a problem in most greenhouses at springtime.

The seedlings, which look like blades of grass, will appear within two weeks. Remove the weaker of the two to leave one per pot or outdoor sowing station. Keep the covers in place outside as the plants grow, and only remove them once the young plants touch the tops of the cloches or reach 10cm in height under the fleece.

Greenhouse or indoor-raised seedlings can be planted out when they are about 15cm tall and after all chances of frost have gone. Harden them off beforehand by gradually introducing them to their new home over a week or two. Plant them out at the same spacings as you would directly-sown seeds. Water thoroughly to settle the soil around them, and keep the young plants tenderly watered as they establish.

Sweet corn is very easy to grow once plants are established and is rarely affected by pests and diseases. However, to maintain a steady rate of growth you will need to water consistently after the feathery male and silky female flowers appear. At this stage, plants will grow better if given a liquid feed that’s high in potash – any organic tomato feed should do the job, applied as per the packet instructions, usually once or twice a fortnight. You can help the pollination process by gently tapping or shaking the plants after the male flowers appear.

Plants can reach up to 1.8m tall, which means that if your site isn’t well sheltered you may need to individually stake plants by tying them into bamboo canes wedged next to them. Another method of offering extra support is to bank up the soil against the base of each stem into which new roots can grow to anchor the plant. If any roots appear above ground you will, in any case, need to cover them over with soil or compost. Side shoots, known as tillers, may also appear near the base – leave these intact, as removing them can reduce the yield.

Early varieties of sweet corn will yield their first cobs in late July or early August, while the season comes to a close with late-developing types in October. An old American saying advises that you should walk to the plants to harvest your cobs and run back with them – a tradition worth adhering to, because freshness is of the essence! A flat sprint may be a little extreme, but it is true that the high sugar levels that have been bred into sweet corn begin converting to starch within hours of picking. That’s why the taste of freshly-plucked home-grown corn is so superior to shop-bought versions.

You will know it is almost time for picking when the silky tassels on the developing cobs turn a chocolate brown and start to wither. At this point, gently peel back the protective sheath to inspect the corn. Squeeze a kernel with your thumb nail. If a clear liquid oozes out then wait a little while longer, but if a creamy elixir appears then it’s time to pick your crop. If there’s no liquid you have waited too long. Harvest the cobs by twisting them sharply away from the plant, or use a pair of secateurs to cut them free. In a good summer you may get two per plant but don’t be disappointed if you only achieve one.

Month-by-Month

  • January

    Carry on preparing planting and sowing sites as long as the soil isn't wet or frozen.

  • February

    Carry on preparing planting and sowing sites as long as the soil isn't wet or frozen.

  • March

    Carry on preparing planting and sowing sites as long as the soil isn't wet or frozen.

  • April

    Sow sweet corn under cover into fibre pots or loo roll centres so the roots can break through. Use a seed or multipurpose compost and sow two seeds per pot about 2cm deep.

  • May

    Sow seeds outdoors under cloches or coverings of fleece. Plant out indoor-sown seedlings once all risk of frost has subsided.

  • June

    Continue planting out. Keep covers in place as long as possible to give the plants a good start and increase the chances of them successfully maturing to flower.

  • July

    Maintain a steady supply of water and high potash liquid feed once the flowers appear. Gently tap the plants to dislodge the male pollen.

  • August

    Continue feeding and watering your plants to guarantee the speedy development of your cobs. Stake tall plants in exposed locations.

  • September

    This is the usual month for harvesting sweet corn, starting with the early varieties and ending with the late varieties – although in good years you may continue to enjoy yields into October.

  • October

    Finish harvesting your sweet corn and then dig up and compost the old plants.

  • November

    Start digging over the site for next season's crop. Incorporate generous amounts of organic matter as you work the soil.

  • December

    Carry on preparing planting and sowing sites as long as the soil isn't wet or frozen.

Next
Spaced Out

Spaced Out

Sweet corn may seem like a fairly inefficient crop as it occupies a large amount of space for the entire growing season, but it is still worth growing even in small gardens. The open habit of the plants, with most of the leafy growth at the top, means that light can penetrate right to the ground. Up to a month before harvest there will still be plenty of light, air and moisture at this low level. So the ground at the base can be used to cultivate another quickgrowing crop. Leafy salads such as lettuce or rocket, radishes, spring onions and even speedy varieties of turnip or dwarf French beans are all excellent choices. By the time the sweet corn plants really fill out, the base plant will have been long harvested. This technique, known as intercropping, offers an efficient way of taking advantage of space between plants that need a lot of room but take some time to reach maturity.

Sweet Corn: Varieties To Try

  • Sundance

    Widely regarded as one of the very best varieties of sweet corn. It reaches maturity quickly and will form a decent crop even in poor summers. The 18cm-long cobs are packed with sweet, creamy-yellow kernels that will have you coming back for more.

  • Minipop

    Baby sweet corn is delicious in stir-fries or raw in salads – and it’s a great crop to get kids into growing their own. This variety is productive and the compact cobs taste delicious. It can be grown in a row and doesn’t require pollination.

  • Swift

    This is one of the earliest varieties to reach harvest time. The medium sized cobs are exceptionally sweet and tender and the plants are welladapted to the unpredictable British summer. It produces a high yield too!

  • Tuxedo

    This tally variety has a high sugar content and can be ready just 85 days after planting out. The cobs are long, at 21cm, and well filled. A tough variety that can cope with dry weather and that’s disease tolerant.

  • Honey Bantam Bicolor

    The stunning cobs form a mix of creamy white and yellow kernels that make for an interesting choice. It’s also incredibly sweet, so it’s perfect for eating freshly boiled. The cobs are tender and are formed early on in the cropping season.

Blowing In The Wind

Sweet corn is in fact a type of grass (specifically maize). The plants have been bred to develop an exceptionally high natural sugar content within the cob – sufficient to make it suitable for eating unprocessed as a succulent treat in its own right. All grasses are pollinated by the wind, rather than by insects. It is for this reason that sweet corn is traditionally planted in blocks rather than long rows, as the falling pollen will have a greater chance of striking females flowers in a close-knit arrangement.

The male flowers are the feathery, upright blooms that project from the top of the plants. Their exposed position allows them to catch the wind and release their clouds of pollen. The fine pollen particles gradually drift down into the crop to come into contact with the female flowers, which are about halfway down the plants. It is the female bloom that produces the corn cob, once it has been fertilised by the male pollen. Female flowers take the form of long tassels, perfectly designed to catch any passing pollen and lock it into place for fertilisation. In still conditions tapping the plants greatly helps pollination and the formation of more evenly-distributed cobs.

Sweet Corn

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