Grow Sweetcorn At Home: Everything You Need To Know

Sweetcorn tastes best when eaten as soon as it’s picked and the only way you can enjoy that fresh, super-sweet taste is to grow sweetcorn at home.

In this article, I’ll walk through every step you need to take to grow your own corn – from sowing seeds and what varieties to pick all the way down to details such as where to grow your plants and the optimum layout and spacing to maximise yield.

If you have any questions, leave a comment and I’ll get back to you!

When To Grow Sweetcorn

The best time to start growing sweetcorn is around your last frost date as cobs can take 2 to 4 months to form and ripen, depending on the variety & conditions. Sweetcorn is a tender annual that can’t be exposed to frost so it’s best to plant early, especially if your growing season is short.

The best month to direct sow sweetcorn outdoors in the UK is usually May or June but check your last frost date in your area and wait until it has passed. If you sow indoors, then you can sow sweetcorn seeds up to four weeks earlier.

What Are The Best Sweetcorn Varieties?

There is a seemingly endless selection of sweetcorn varieties out there. This is my ‘must-grow’ list, filled with varieties that I want to grow which contains personal recommendations or varieties that I was impressed with before and will definitely grow again.

Hybrids & Modern Varieties

• Swift (F1) – Good for quick harvests, only requires 90 days from planting
• Earlibird – Allegedly it holds the record for the earliest supersweet crop in Europe
• Conqueror (F1) – As the name suggests, this one produces giant cobs. Tastes good too!
• Lark (F1) – Another popular and tender sweet variety. I’ve not grown it but apparently it is less chewy

Heirloom & Traditional Varieties

• Glass Gem – Produces a multicoloured cob that is great for making flour and for it’s ornamental value. Grow until the corns are hard which may take 4 months. A modern breed but will grow true to type each year.
• Fiesta – A traditional multi-colour cob with deeper, more intense colours. Another flint type grown to be ground down.
• Dolce – Popular golden yellow and sweet variety. 80 days to harvest.
• Golden Bantam – Fast growing heirloom producing bright yellow cobs.

How To Sow Sweetcorn Seeds

Indoor Germination

Sweetcorn can be hit-or-miss when it comes to germination outside. Therefore starting plants indoors can be a very useful step for those who want a head start and get an early harvest, or those who want to save money on seeds. It also stops mice digging up the kernels before they can sprout.

I prefer to place my sweetcorn in between two layers of wet paper towels in a sealed container and allow the seeds to soak up the water and germinate. Check them each day and as soon as you see a root, plant each seed in 3 inch pot. The stem will appear and grow perpendicular to the ground shortly after the root emerges so it’s important to get the seed’s orientation right early on.

Alternatively you can sow seeds into pots at a 2.5cm (1 inch) depth from the surface and avoid all the fuss. If the soil is loose and the conditions are warm and moist, you should still get good germination, although poor quality, dense and cold seed composts may see lower rates. You can a propagator or cling film to keep the moisture in. Otherwise, make sure the pot doesn’t completely dry out.

Germination should take anywhere from 3 – 10 days depending on the variety, the amount of moisture in the container and the temperature. If you’ve got a sunny windowsill or an airing cupboard, use it to speed up the process.

2 to 3 weeks after planting, the sweetcorn seedlings should be large enough to transplant into the ground. Wet the container so the soil isn’t loose, use a dibber to make a hole in the ground and then transfer the sweetcorn by tipping the pot upside down with the plant stem going through your fingers. Lift away the pot, invert the plant and the soil and gently place it in the hole and try to firm it in as much as you can. If you can avoid it, try not to disturb the roots.

Direct Sowing

Sweetcorn doesn’t like having its roots disturbed so many people prefer to direct sow sweetcorn and let it grow outdoors from start to finish. Plant seeds 2.5cm or 1 inch below the surface and cover with compost.

You may need to sow multiple seeds – two or three per hole – to account for lower germination rates outdoors, which vary with temperature. Sweetcorn needs the soil to be warm for the seeds to germinate so it can sometimes be better to wait until June.

While direct sowing is the easiest option, be prepared to replace any seeds that get dug up or disturbed by mice or knocked over by birds. And be on the lookout for hungry slugs and snails who will happily feast on your young plants.

It’s also really important that you take the time to get the correct spacing between plants, otherwise you might end up with incomplete pollination or even completely empty cobs…

Ideal Growing Conditions For Sweetcorn

How To Space Sweetcorn For Maximum Yield

Sweetcorn is wind pollinated. The tassels at the very top are the male part of the plant and release pollen which should land on the silks that protrude from the wrapped empty cobs (which are called ‘ears’) below. If the plants grow too far apart then the probability that all of the silks are fertilised drops and, unfortunately, silks that do not get fertilised do not grow into the fleshy tasty kernels we want to grow. Instead you get cobs of corn with gaps in them and therefore less sweetcorn.

To get full cobs of sweetcorn, it’s essential that you plant in blocks and not in straight rows to ensure that plants are surrounded by a neighbour and it’s important that you plant them the right distance apart. The recommended spacing is 35 to 45cm (14-18 inches) but it varies by climate, soil, variety and nutrient availability.

Researchers tend to find denser plantings produce higher yields in commercial settings with 9 plants per square metre (55cm rows with 20cm spacing) being optimal in this Iranian study and 7.4 plants per square metre (70cm rows with 20cm spacing in an organic setting in Indonesia – although they didn’t test narrower rows). While this paper studying hybrid plants in Illinois, would suggest 6.1 to 8.7 sweetcorn plants per square metre is optimal.

A square grid of sweetcorn with 35cm spacing is broadly optimal for commercial hybrids at a planting density of 8 plants per square metre but you could consider widening the grid if growing less vigorous or traditional varieties or if your soil is poor.

This year I will also be doing a side-by-side comparison between a regular square grid and a hexagonal grid. This trick of geometry (thanks Pythagoras) allows you to either pack more plants into a given area and improve pollination or you can keep the density the same as a square grid but place plants a little further apart if you are concerned about competition for resources e.g. if plants are too close, they will compete for light. Mathematically speaking, a hexagonal planting scheme at 9.2 plants per square metre (or 1.15 times greater than the ideal square grid planting) should be optimal.

Sweetcorn Needs Full Sun

Too much shade can significantly limit the growth of sweetcorn plants, especially early in the season and while the plant is young. A lack of sun and heat will also delay ripening of the cobs. It’s therefore best to plant sweetcorn where it can get full-sun for as many hours as possible.

It’s also important to think about light towards the end of the year – as the sun dwindles and doesn’t climb as high in the sky, will it still cast light on your plants? Around the spring equinox, take some time to observe and ensure your planned growing area won’t be too shady in September.

Do Sweetcorn Plants Need Support?

Sweetcorn doesn’t need staking in place. The plants anchor themselves into the ground through the roots and the brace roots at the base. However they may benefit from additional support in windy or exposed areas.

If you are growing sweetcorn in containers then use a large container as the plant and cobs will be limited by the amount of available soil and I would suggest staking the plant by tying the stalks to a bamboo pole inserted at the time of planting.

Alternatively, you could move the container into a greenhouse and grow your plants under cover.

Can I Grow Sweetcorn In The UK?

There is more than enough heat and light to grow sweetcorn outside in the UK except in the far north and you do not need a greenhouse. Sweetcorn grows successfully on commercial farms and in domestic gardens. Common varieties should yield fresh or dried corn before the first frosts in late Autumn.

Watering Sweetcorn

Sweetcorn has a shallow root system. The depth will vary based on conditions, in particular soil moisture and soil type, but 85% of the root mass is in the first 30cm of soil. This is where most of the water and nutrient absorption takes place.

Like most grasses, sweetcorn is relatively drought resistant but it does prefer regular watering, especially when the plant is young and the root system is immature. While the cobs are forming and ripening we want to ensure the plant doesn’t dry out or it will impact yield.

Unless there is a significant drought, a thick layer of mulch around the base should be sufficient to prevent sweetcorn plants from drying out even in the dry eastern half of the UK. But monitor your local conditions and apply water if the soil is dry a few inches down in the soil.

I water my plants using a soaker hose on a timer and try and get a mulch layer down on my garden beds by the middle of July. Read this article about installing soaker hoses to see if they can make watering your sweetcorn patch hassle free.

Feeding Sweetcorn

Application of organic matter such as manure in the autumn before planting or organic compost up until the time of planting should provide sufficient nutrients for the plants. However sweetcorn is a grass and therefore consumes significant amounts of nitrogen while growing, so applying a nitrogen feed or a nitrogen-releasing mulch could improve growth rate and final plant height.

Like most fruiting plants, while the cobs are forming and ripening, the plant’s nutrient requirement will shift away from nitrogen and towards phosphorous and potassium. Using an organic tomato feed or a seaweed fertiliser would be appropriate at this stage.

I personally do not feed my sweetcorn plants at all during the season and instead rely on an application of organic compost in the spring every other year and apply a layer of grass clippings as a mulch which I keep topped up as needed.

Harvesting Sweetcorn

When Is Sweetcorn Ready To Pick?

After fertilisation, the cobs will begin to fill-out and get heavier. You may start to see the plant buckling around the ears. The silks will shrink and start to turn brown and they will darken over time until they reach a chocolate-like colour. This means it’s time to harvest!

Before harvesting, you should check the sweetcorn to ensure it’s turned ripe. The classic test is the ‘fingernail test’. Peel back a few leaves from the husk and pierce one of the kernels. If the liquid looks milky, it’s ready to eat. If it’s clear and watery, it’ll need a little while longer.

To harvest sweetcorn, hold the stem of the plant in one hand, an ear in your other hand (as if you are holding a torch) and then simultaneously rotate the ear and and twist your hand downwards. The ear should come away clean from the plant.

You can then remove the brown silks, unfurl the husk and throw that sweetcorn on a barbecue or straight into a pan. Sweetcorn looses flavour every second it’s off the plant, so cook your sweetcorn as soon as possible after harvest (ideally straight away). It’ll still be edible for a few days if it’s kept in the fridge and it’ll last longer if you keep it wrapped up in it’s husk, but it won’t quite be as good.

Drying Sweetcorn

If no liquid comes out during the fingernail test or if the kernels are really hard, then you are probably too late and it might be best to leave the corn on the plant to mature further and instead use it as a flour or corn-meal or as seed for next year.

To harvest corn for drying, wait until the husks are starting to yellow and then pull the ears from the plant via a twist and a tug. Peel back the husk but keep the leaves attached – use them to hang the sweetcorn until the kernels have fully dried. I do this in a plastic greenhouse for a month and then remove and store the seeds indoors.

Can You Leave Sweetcorn On The Plant?

It is possible to leave the plants standing with the ears still attached through the autumn (and winter) and let the sweetcorn kernels dry out naturally. Moisture and rot can be an issue and even under favourable conditions, you might find a small amount of fluffy mould on the seed coating. But I managed to harvest some glass gem seeds in May – a full 12 months after planting. They haven’t germinated yet, mind…

Can You Use Sweetcorn Kernels As Seeds Next Year?

If you grow heirloom varieties, then you can dry and save the seeds in the autumn and they will grow true to type the following year. If you grow hybrids or if you plant many varieties together, you can still use the seed but the plant might not be the same and the corn could taste quite different.

Most sweetcorn seeds have a shelf-life of a few years. Best before dates on packets are usually 1-2 years but you’ll get reasonable germination long after that if they are stored in a low temperature and low humidity environment away from any bright lights, particularly sunlight.

Is Growing Sweetcorn Worth It?

Sweetcorn is one of the best crops to grow at home because it’s very low maintenance and it’s impossible to get sweetcorn that fresh or that tasty in a shop. You can grow slower-growing, tastier varieties and even colourful ornamental cobs or you can make your own corn-meal from the dried kernels.

Because supermarkets can’t provide any of this and because sweetcorn is relatively easy to grow, I make sure to grow a least a small amount of it somewhere in my garden each year. I hope you find a place in your garden to do the same.

Happy Gardening!