Tomatoes are sun-lovers from South America, and the British climate rarely gives them the heat they crave. The single biggest factor in success is finding the warmest, most sheltered spot you have. A south-facing wall, fence or greenhouse is ideal. On an allotment, choose the sunniest bed and avoid low, frosty corners where cold air collects.
If growing outdoors, plan to give plants protection for at least the first few weeks. Cloches, fleece, or a temporary polythene frame can make the difference between a crop and a disappointment. Under glass, a cold greenhouse or polytunnel works well, but ventilate on sunny days to prevent scorching and disease.
Not all tomatoes are equal in a cool, damp climate. Look for early-maturing, blight-resistant or compact varieties. Cherry tomatoes often ripen more reliably than large beefsteaks because they need less accumulated heat. If you grow outdoors, bush varieties are easier than tall cordons, which need more attention.
Growing a mix spreads the risk. If blight strikes one variety, others may survive. Save seed from your best plants if you want to adapt them to your own plot over time.
Sow indoors or in a heated propagator from late February to early April. Sow seeds about 1cm deep in moist seed compost. Keep them at around 18–21°C. Once seedlings have two true leaves, prick them out into 9cm pots. Grow them on in good light; leggy plants never fully recover.
Plant out only after the last frost, usually late May or early June in southern Britain, and early to mid-June further north. Harden plants off over 7–10 days by putting them outside in a sheltered spot during the day and bringing them in at night. Bury the stem deeper than it was in the pot—roots will form along the buried stem, making a stronger plant. Space cordons 45–60cm apart, bush varieties a little closer. Grow bags and 10–15 litre pots are fine, but ring culture or a bottomless pot sunk into the border helps roots access extra moisture and nutrients.
Tomatoes hate extremes. Dry compost followed by a soaking causes split fruit and blossom end rot. Aim for consistently moist soil, watering little and often in warm weather. In pots, this may mean twice a day during a heatwave. Water the compost, not the leaves, and do it in the morning so foliage dries before evening. Irregular watering is the main cause of blossom end rot, not simply a lack of calcium.
Cordon tomatoes need a cane or string support and regular tying in. Remove the sideshoots that grow between the main stem and each leaf—snap them out when small. Once a cordon has four or five trusses outdoors, pinch out the growing tip to direct energy into ripening. Under glass you can allow six to eight trusses. Bush tomatoes need no pruning, though a light trim of overcrowded leaves improves airflow.
Tapping flower trusses gently at midday helps pollination, especially in still air. As fruit ripens, remove lower leaves that shade it and reduce watering slightly to concentrate flavour. At the end of the season, green tomatoes can be ripened indoors on a sunny windowsill or in a paper bag with a ripe banana. Never put them in direct sun behind glass—they cook rather than ripen.
Blight is the great British tomato enemy. It thrives in warm, humid weather, usually from July onwards. Brown patches on leaves and stems spread fast. Remove affected foliage immediately, improve ventilation, and avoid overhead watering. If blight is a regular problem, grow resistant varieties or keep plants under cover. Outdoor growers in wet regions may get a better crop from a polytunnel or a simple plastic canopy than from open ground.
Cool spells slow growth and ripening. Fleece over hoops can extend the season by a few weeks in autumn. Watch for aphids and whitefly, especially under glass; encourage ladybirds and hoverflies, or spray with soapy water. Slugs and snails attack young seedlings—use barriers or night patrols. With a little planning and regular attention, even a damp British summer can deliver bowls of warm, home-grown tomatoes.
Gate & Furrow shares practical, down-to-earth guidance on british kitchen gardening and allotment growing for readers across the UK.
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