Greetings crop pickers, here's the run down of the current top 12 polytunnel crops. Each of our 'Top of the Crops' have detailed growing guides, working with author and long-time polytunnel gardener, Andy McKee, we have produced a series of guides complete with all the do's and don'ts of growing the most popular crops. Whether you are looking to try growing something new, or just want to improve your existing crops these guides will make sure your polytunnel gardening is a big hit with all the family...
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Rewarding and generally problem-free, sweetcorn is easy to grow outside in most of England but becomes harder the further north you go, with harvests becoming unreliable any further north than Yorkshire. Using a polytunnel, however, you can grow sweetcorn successfully in the Shetland Islands – and gardeners in the south can use their poly tunnel to harvest perfect ears of corn weeks earlier than their outdoor plants. Sweetcorn loves the rich soil and protection from high winds inside a polytunnel, and once germinated they don’t need much attention beyond keeping them well fed.
Sweetcorn loses sweetness from the moment it is picked, which means that homegrown corn tastes far better than corn bought in the supermarket. It does take up quite a bit of space, but the leaves let a lot of light through to the ground which means you can grow other plants (particularly low-growing legumes like dwarf french beans) between them.
Varieties: Butterscotch (for far northern areas) and Swift. Keep seed for no longer than a year, as the quality suffers with storage.
Sowing: Sweetcorn can be sown direct in the polytunnel in mid-May, but for the earliest harvest they should be started off on a sunny windowsill indoors from mid-April to early May. Sweetcorn plants hate root disturbance, so plant them 2.5cm deep in biodegradable pots, allowing two seeds per tube to account for failures. Ordinary potting compost is fine.
If you haven't already prepared the bed for
sweetcorn, get it done when you sow: incorporate
lots of compost into the soil and add a handful of
bonemeal per square meter, then water the bed
To make sure that sweetcorn is pollinated properly, it is best grown in a block rather than in rows or singly. As soon as roots start to push through the cardboard, plant the seedlings, pot and all, into their final positions allowing a minimum spacing of 15cm x 25cm. As they grow, the plants may produce side-shoots, but there’s no need to remove them.
Once the plants are established, begin feeding with tomato fertilizer every fortnight, and keep this up until you harvest. Increase the amount of water you give once the ears begin to form, but never allow the bed to become waterlogged. When the tall feathery 'tassels' (male flowers) appear at the top of the plants, tap the stems each morning so that the powdery pollen falls from them.
Diseases and pests: The only likely problem in the UK is theft – usually by rodents, but if you’re really unlucky by badgers or deer – once the corn begins to ripen. If your poly tunnel receives unwanted attention, harvest the remaining ears as soon as possible.
Harvest from July to September. As soon as the silks on the end of the ears of corn turn brown and start to shrivel up, you can test to see if the kernels are ripe. Gently peel one ear open a little to see the kernels, and pop one with your fingernail. If the liquid is watery, leave the corn a few more days; if it's creamy, the corn is ready to harvest. Any ears you don't want right away will keep best on the plant, but don't leave them too long. If popping a kernel shows that the liquid inside is becoming doughy, the corn is overripe – harvest the rest immediately.
Recipe: By far the tastiest way to enjoy sweetcorn is to take it straight from the plant to the barbeque. Twist whole ears from the plant and put them, without removing any of the outer leaves, into a bucket of cold water. After leaving them to soak for half an hour take them out, give them a bit of a shake, and put them on the BBQ grill for 25 minutes, turning several times to distribute the heat. The outer leaves will turn black, but when you peel them away the corn will be perfect and ready to eat straight away. Just try not to burn your mouth...