Tomato Facts

Growing Methods

• In Britain practically all tomatoes are grown commercially in glasshouses, although some were still grown outdoors in Jersey until recently. Heated glasshouses allow the season to be extended from February until November, with all year round production being evaluated. Under outdoor conditions, tomatoes can only be cultivated between July and October in this country and success depends very much on what sort of a summer we have.

• Production is far higher under glasshouse conditions than from outdoor field crops, or crops grown under plastic in southern Europe. It takes up to five times the area of polythene in Spain to grow the same quantity of tomatoes as in British glasshouses.

• Tomatoes are easily damaged by the wind, extremes of temperature or fluctuating weather conditions. Glasshouses offer not only a longer growing season, but also provide shelter from the weather and protection from birds and animals.

• Under glasshouse conditions, the aerial environment and crop irrigation and nutrition can be precisely controlled. This also gives the opportunity to avoid disease infection and to use natural predators to control pests instead of sprays. As an example, potato blight has been a serious problem in outdoor and back garden tomato crops in the last few summers because of wet weather. This is not a problem in commercial glasshouse crops, without having to use fungicide sprays. Simply by keeping the plants dry at all times, blight infection can be kept at bay.

• Closed irrigation systems are increasingly used i.e. excess water and nutrients are re-cycled, while leaves and old plants are composted, rather than being dumped. Cultural systems in Britain are designed to minimise any impact on the environment.

• Most British tomato crops are now grown in rockwool, the modern equivalent of grow bags, with which many gardeners will be familiar. This has replaced the use of peat, which is no longer favoured for environmental reasons. Rockwool provides ideal growing conditions for the roots and produces better crops as a result. It is also much lighter for nursery staff to handle.

• Bumblebees are used for pollination and pests are controlled using natural predators. These are introduced to the crop instead of using chemical sprays. British growers aim to use no pesticides and a significant area of organic crops is being produced. The full range of different tomato types produced to Organic standards is available.

• Flavour in tomatoes is related to the sugar and acid concentration in the fruit and to the organoleptic content (natural aromas and volatile compounds). For the best flavour, high sugars and relatively high acids are required. High acids and low sugars will produce a sharp-tasting tomato, whereas when both sugar and acid levels are low, the flavour is bland.

• It takes 40-60 days from a flower for a tomato fruit to reach full ripeness, depending on the temperature and the variety. Cherry tomatoes ripen a little more quickly than larger-fruited varieties.

• No genetically modified tomatoes are grown commercially in Britain.

• Sunlight increases tomato yields, rather than warm temperatures. In fact, very hot weather may reduce yields and give poorer flavour and a shorter shelf-life. High temperatures also reduce the concentration of the red tomato pigment lycopene, which is receiving a lot of attention because of its potential health protecting properties. The optimum temperature for lycopene synthesis in tomato fruits is 16-21°C, exactly the range at which British growers aim to control the temperature of their glasshouses.

• It takes 1-3 days for a British tomato to be on display in the shop from the time it is harvested.