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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Tomatoes are one of the most popular plants for UK gardeners to grow. They're moderately fussy plants, needing constant feeding, frequent watering, and a calm and sunny spot. Despite all this they're very rewarding, and with so many varieties available you can try a new one every year if you like. Growing in your polytunnel lets you grow serious amounts of tomatoes, and frees you from the few varieties that will tolerate being grown outdoors. Your biggest headache will be choosing which ones to grow next; purple or striped fruit, sharp or sweet, huge and fleshy or tiny and juicy?
Varieties: 'Latah', 'Red Cluster Pear', 'Harbinger'
Sowing: Tomatoes are not difficult to grow from seed, but the key to getting good results is to give your plants the longest growing season you can. In most of the country getting things started early on a sunny windowsill is fine, but in northerly areas it is better to buy young plants from a local nursery, which will have kick-started the whole process for you using heat and growing lights.
For strong plants without the risk of stunting, tomato seeds should be sown in modules of seed compost around the middle of March and given a warm and well-lit spot, such as an indoor windowsill, until they can be brought out to the polytunnel some time in April. Sow seeds into 9cm pots, 0.5cm deep. Germination is usually good, so don't sow more than two or three to a pot, and thin to the best plant when they're 2 or 3cm tall.
When roots appear at the bottom of the plant pots, pot your seedlings on into larger pots of potting compost. Unlike most other plants, tomatoes will tolerate being planted so deeply that only their top set of leaves are left above the surface; the buried portion will sprout more roots, giving a stronger plant. Wait until the first flowers have formed before you set tomato plants out into their final growing positions in the soil beds, or in large pots or grow bags.
When planting tomatoes into the soil beds, dig lots of fresh compost and a handful of comfrey pellets into each planting spot. Don't make the mistake of crowding in too many plants, as good airflow round the leaves is vitally important to reduce the chance of tomato blight (see 'harvest' tab) infecting your polytunnel. Leave at least as much space as the seed merchant recommends, and provide a support for each plant. Tie them in every 25cm or so, and nip off any side-shoots that develop from the leaf joints so that you are left with a single upright vine.
Tomatoes are hungry plants and need to be fed with tomato fertilizer starting as soon as the first flowers appear, but watering is absolutely crucial for top-quality fruit. Never let the soil dry out - and this makes growbags less than ideal. If you do opt for them, use two to make an extra deep one: put one on top of the other, and push your trowel through the bottom of the top bag. Your plants will soon find the hole, and will be glad of the extra moisture on hot days.
Diseases and pests: Tomatoes can be affected by whitefly, red spider mites, aphids and various foliage diseases, but by far the most serious problem is blight, which can occur any time from early July. Tomato blight starts as a irregular shadowy patches on the leaves which turn into a watery rot that causes foliage to collapse, shrivel and turn brown. Blight spreads quickly in the humid conditions of the polytunnel, but if you spot it early enough you can slow down its advance by removing infected foliage (burn it, bin it, or bury it deep inside a hot compost heap) and spraying the remaining plants with 10g of sodium bicarbonate (baking soda) in a litre of water.
Harvest from June/July
Unlike shop-bought fruit, properly ripe tomatoes should give a little when squeezed gently. Harvest each fruit as it becomes ripe, levering it up so that the calyx (the little tuft of green leaves at the top of the fruit) comes with it, and use within a few days. Fruit kept in the fridge will keep for a couple of weeks but the flavour weakens with storage. And what flavour!