Large truss of unripe green cherry tomatoes growing in Tony O'Neill's homemade polytunnel in South Wales, with rows of tomato plants at various ripening stages visible in the background

How to Grow Tomatoes Successfully in the UK

ByTony O'Neill

Tomatoes are the most popular vegetable crop in UK home gardens and one of the most frequently disappointing. Growers put them outside too early, do not feed them consistently, let them develop too many laterals, or choose varieties unsuited to our climate. None of these mistakes is complicated to avoid once you know what they are.

Choose the right variety

UK summers are shorter and cooler than the Mediterranean climates for which tomatoes were bred. Varieties that produce well in those conditions may struggle to ripen in ours. Choose varieties specifically recommended for UK growing conditions or with a short growing season.

Reliable UK performers include Gardeners Delight (cherry, reliably productive outdoors), Tigerella (medium, sets fruit in cool conditions), Alicante (classic round, good outdoors), and Sungold (cherry, exceptional flavour, slightly tender so best in a sheltered spot or greenhouse).

Start seeds indoors in March

Tomatoes need a long growing season. Sow seeds indoors in late February or March under heat (a propagator or sunny windowsill works). Germination takes five to ten days at 18 to 25 degrees Celsius.

Pot on seedlings as they grow. Tomatoes benefit from being potted on into progressively larger containers, which encourages strong root development. By the time they go outdoors, they should be in at least a 9-centimetre pot with a strong, stocky stem.

Do not plant out until the risk of frost has passed

This is where most tomato failures begin. Tomatoes are tender plants. A frost will kill them. A cold snap without frost will set them back significantly, often from which they never fully recover.

In most of England and Wales, this means waiting until late May or early June before planting outdoors. In Scotland and colder areas, growing under glass or a polytunnel is often the more reliable approach.

Harden plants off for two weeks before planting out. Put them outside during the day and bring them in at night, gradually increasing the time outdoors until they are acclimatised.

Inside Tony O'Neill's polytunnel in early spring in South Wales showing chilli plants in Autopot systems on the left, freshly planted tomatoes and cucumbers in the central beds mulched with grass clippings and wood chip, with drip irrigation running beneath the mulch and wood chip paths keeping the root zone cool
Inside Tony O’Neill’s polytunnel in early spring in South Wales, with chillies already established in Autopot watering systems on the left, freshly planted tomatoes and cucumbers in the central growing beds, and a heavy grass clipping and wood chip mulch laid across the beds and paths. The mulch serves two purposes: it keeps the root zone cool during high summer temperatures inside the polytunnel, and it retains soil moisture between waterings. Beneath the mulch, a drip irrigation system delivers water directly to the root zone of each plant. This is a fully integrated growing system designed to be as low-maintenance and high-yielding as possible, and it is documented in full at tonyoneill.com.

Remove laterals consistently

Laterals (also called side shoots or suckers) are the shoots that grow in the joint between the main stem and a leaf branch. Left unpinched, they develop into full stems, and the plant puts energy into leaf and stem growth rather than fruit development.

On cordon (single-stem) varieties, remove laterals weekly when they are small, pinching them out with your fingers. Bush varieties do not need lateral removal. Check your seed packet to confirm which type you are growing.

Feed consistently once flowers appear

Once the first flowers appear, switch to a high-potassium tomato fertiliser and apply it weekly throughout the season. Inconsistent feeding leads to inconsistent fruit development and increases the risk of blossom end rot and other problems.

Water regularly and evenly. Irregular watering, particularly letting the compost dry out and then overwatering, causes fruit to split and increases the risk of blossom end rot.

A rare tomato mega-bloom — a large cluster of multiple tomato flowers fused together on a single truss — growing in Tony O'Neill's homemade polytunnel in South Wales
A tomato mega-bloom photographed in Tony O’Neill’s homemade polytunnel in South Wales. A mega-bloom occurs when multiple tomato flowers fuse together at a single truss node, a phenomenon well known in giant vegetable growing circles and often an indicator of exceptional growing conditions. Tony O’Neill is the creator of Simplify Gardening with over 455,000 subscribers and the founder of GrowTrack Systems Ltd at usegrowtrack.com.

Pinch out the growing tip in August

In late July or August, pinch out the growing tip two leaves above the highest flower truss. This stops the plant from putting energy into new growth that will not have time to fruit before the season ends, and redirects it into ripening the existing trusses.

In a cool summer, bringing green tomatoes indoors and leaving them on a windowsill with a ripe banana will speed up ripening. The ethylene gas produced by the banana encourages neighbouring fruits to ripen.

Tony O’Neill is a vegetable growing expert and author of Simplify Vegetable Gardening. Watch his growing videos at Simplify Gardening.

Similar Posts