Growing Sweetcorn


Growing sweetcorn is an absolute must each year. Shop bought sweetcorn tastes nothing like the sweet, tender freshly picked cobs from the allotment. Ideally cooked within hours of picking to maximize that sweet flavour, with lashings of salted butter. Totally delicious.

Sweetcorn doesn’t belong to any particular cultivar; it’s actually a type of grass. The advantage of this is it can be slotted in any convenient position on the allotment, providing it’s not grown in the same position for too many years in a row.

There are various types of sweetcorn, old varieties, super sweet varieties and extra super sweet varieties. As the name suggests, the super sweet varieties are sweeter than the old varieties, and they retain their sweetness for longer. However, they are less vigorous. The extra super sweet sweetcorn is just a less chewy form of super sweet sweetcorn.

Sweetcorn is extremely tender and will not tolerate exposure to the cold. It grows best when the summers are hot and sunny.

I’ve found, given the external challenges of slugs, mice and birds, plus April’s unpredictable weather, it’s definitely best to start sweetcorn off at home in modules.

Growing Sweetcorn from Seed

Sow seeds indoors from mid April to early May.

Sweetcorn seeds germinate best at temperatures of between 65F to 70F. Seeds will not germinate if the soil temperature is below 50F.

Sweetcorn doesn’t like root disturbance, so sow seeds in deep 7.5cm pots or deep root trainers, at a depth of 2.5 cm using good quality compost.

Water well, label and either cover with cling film/propagator lid and place on a sunny windowsill, or place in a heated propagator.

Germination should take between 5 to 10 days. Although, super sweet varieties are tricky to germinate, the seeds are more likely to rot especially in cool damp conditions.

Once the seedlings are well established, 10 to 15cm high move the pots outside to a cold frame to harden them off before planting them in May/June. Ensure that there is no risk of frost before transferring them outside.

Choose a sunny, sheltered site that has rich fertile well-drained soil.

For pollination purposes, plant sweetcorn in blocks rather than rows. The block should ideally be 4 rows by 4 rows or larger.

Plants should be spaced 40cm to 45cm apart.

Once planted, water them in well and cover with mulch.

Sweetcorn plants don’t need too much attention as they grow. Keep them watered and weed free.

Watering is essential whilst the plants are flowering and the cobs begin to swell. The plants also benefit from liquid feed once the cobs begin to swell. This should help the development of properly formed cobs.

Sweetcorn flowers

Sweetcorn plants, like all grasses, are wind pollinated.

As the plant matures it produces both male and female flowers.

The male flower or tassel is located at the top of the plant; the tassel is full of the plants pollen. Plant sweetcorn in blocks to ensure pollen isn’t just blown away. As the wind blows through the plants tassels pollen is released down to the female flowers or silks.

The female flower or silks is situated lower down the plant, on the axle of a leaf and the stem. The female’s sticky silks collect the pollen, which embeds itself. Over the next 12 to 24 hours the pollen grows a tube down the length of the silk. Successful pollination leads to the development of plenty kernels. Poor pollination leads to cobs that have lots of missing kernels.

Sweetcorn plants are in pollination mode for around 10 days. This starts when the male flowers open up and dangle down like bells. The highest quality pollen is usually shed from mid to late morning. To ensure good pollination it may be advisable to assist the plant by hand pollinating. Take some male tassels and brush them against the female silks. This should be repeated a few times over a number of days.

As it’s so easy for pollen to get blown around the allotment don’t grow super sweet cultivars close to other cultivars as cross-pollination reduces sweetness.


Sweetcorn cobs are ready to pick when the silks turn brown. Carefully pull back the leaves and pinch a kernel. If the juice is milky the cob is ready to pick. Harvesting usually takes place from July through to September.

Potential Problems

There are no major problems growing sweetcorn. The main issues are from pests. BADGERS have been known to be quite partial to the odd cob!!! Last year a particularly thuggish gang of magpies destroyed our sweetcorn. We plan to grow many, many more plants this year to avoid dissapointment.


Posted in Sweetcorn

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April 2014
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