Tomatoes are one of the most popular things to grow in a polytunnel – for good reason. Tomatoes will love the extra warmth and protection offered by a polytunnel and will thrive when treated correctly. A polytunnel also makes it easier to control the environment around your tomato plants and it can help to minimise risk of blight. Home grown tomatoes come in all sorts of shapes and sizes and taste far better than the usual supermarket ones.
When buying your tomato seeds, consider choosing heirloom or heritage varieties. These traditional tomato varieties will allow you to collect your own seeds and grow more, better-adapted plants over the coming years. If, however, you know that you have, for example, a bad problem with blight in your area then you may wish to select an appropriate hybrid variety.
In the UK, it is usually a good idea to get started early with your tomato plants so that they are a good size by the time the warmer weather arrives and they can be planted out into an unheated polytunnel – in around April or May. Tomato plants can be sown indoors in a warm place or in a heated propagator as early as January or February.
Once your tomatoes have germinated, you should place them in small pots (or other containers – yoghurt pots and other food packaging works perfectly) on a sunny, warm windowsill. At their early stages of growth, tomato plants will need nitrogen to put on leafy growth. Cool tea can be used to give a nitrogen boost to tomato seedlings. Later, more potash will be required to help form the fruits. Be sure to pot up tomato seedlings when they begin to get too big for their containers, and in the new, bigger containers, plant tomato plants deeper – at least up to the lowest set of leaves. This will help tomato plants to form stronger root systems. This will stand them in good stead in the coming months.
As soon as all risk of frost has passed in your area, harden off your tomatoes and then plant them out into your polytunnel. Again, plant them a little deeper than they were in the pots, into fertile soil that contains plenty of organic material. To make the most of your space, you can cordon your tomato plants, tying them into wire or strings in a vertical fashion. Nip out all side shoots and stop the main growth at the top of your supports. Water tomatoes well, taking care to water deeply rather than little and often. Water roots and try not to get any water on other parts of the plant.
Harvest your tomatoes when they have ripened to the final colour you are expecting. Most tomatoes are red but you can also get red, orange, green, yellow, and purple varieties. At the end of the growing season, pick all the unripe tomatoes and place them in a drawer with some ripe fruits that will exude ethylene gas which will ripen them up.