Why a Wall Makes All the Difference

Tomatoes are Mediterranean plants at heart, and the British summer is always a few degrees short of what they would really like. Siting your pots against a sunny wall buys those degrees back. Brick, stone and render soak up warmth during the day and release it slowly after sunset, keeping plants growing through the night rather than sulking in the cold. A wall also blocks the wind that snaps stems, tears leaves and dries compost out in hours.

Aim for at least six hours of direct sun, and choose a south-, south-east- or west-facing wall if you can. A corner is even better, as the heat gathers and stays. Bear in mind that walls create a rain shadow, so plants against them will need more watering than those out in the open — a small price for a crop that ripens properly.

This same sheltered warmth makes a wall a magnet for pollinators and other wildlife. Plant a few nectar-rich flowers nearby and your tomato corner will be busy with bees from June onwards.

Choosing Compact Varieties

Not every tomato suits a pot. Look at the habit first: cordon (indeterminate) varieties grow tall as a single stem and need staking, while bush (determinate) types stay compact and mostly look after themselves.

• Bush varieties such as 'Tumbling Tom', 'Maskotka' and 'Balconi Red' stay around 30–40cm and let their fruit cascade over the rim. They are perfect for narrow balconies, rail planters and hanging baskets.
• Compact cordons like 'Gardener's Delight' and 'Sungold' need a cane but crop generously in a 15–20 litre pot, and their cherries ripen earlier than most beefsteaks.
• Blight-resistant types such as 'Losetto' and 'Crimson Crush' are worth seeking out for outdoor growing, especially in the damper west of the country.

If you have room for only two pots, plant a bush cherry for early pickings and a blight-resistant cordon for the main season. Cherry tomatoes generally beat large fruiting types outdoors, because they ripen before the weather turns.

Pots, Compost and Planting Up

Size matters more than style. Allow a minimum of 30cm (12in) across, or roughly 10 litres of compost, per bush plant; cordons will repay you handsomely in a 15–20 litre pot. Unglazed terracotta dries out quickly in a sunny spot — plastic or glazed pots hold moisture for far longer. Whatever you choose, check for drainage holes, stand pots on feet so water can escape, and use a saucer in hot spells.

Fill with peat-free multipurpose compost, stirring through a slow-release fertiliser and a couple of handfuls of garden compost or well-rotted manure. Water-retaining granules are a genuine help on windy balconies. Plant deeply, burying the stem right up to the first pair of leaves — tomatoes root along it, which means a sturdier plant and a bigger root system. Water in well and keep the compost damp, not soaked.

Don't rush the planting date. In sheltered city gardens mid-May is usually safe; elsewhere wait until late May or early June. Harden plants off over a week, bringing them in at night at first. If you are sowing your own, start seed indoors from late February to April.

Watering and Feeding

Irregular watering is the single biggest cause of split skins and blossom end rot, so consistency matters more than quantity. Check the compost every morning by pushing a finger in to the first knuckle. On hot days in July and August, that may mean watering twice: once early, once in the early evening.

• Water at the base, in the morning if possible, and keep the foliage dry — wet leaves invite blight.
• Water until it runs out of the drainage holes, then stop. Little and often beats a weekly flood.
• Start feeding when the first truss sets fruit, using a high-potash tomato feed weekly, increasing to twice weekly once plants are cropping heavily.
• Ease off feeding as the season ends, and never overdo nitrogen-rich feeds, which give you lush leaves and few tomatoes.

Support, Pinch and Pollinate

Cordon plants need a cane or a length of string tied to a wall bracket, reaching 1.5m or more. Tie the stem loosely in figure-of-eight loops so it never rubs. Pinch out the side shoots that appear in the angle between leaf and stem each week — small job, big difference. Bush varieties need no pinching; a low ring of string or a short cage is enough to stop them flopping.

Outdoor tomatoes rely on wind and insects to pollinate their flowers. Give each truss a gentle tap mid-morning, or stroke it with a soft brush, and you will see far fewer flowers drop. Underplant with basil, marigolds, borage or nasturtiums to draw in pollinators and hoverflies, and choose single-flowered varieties so the nectar is actually reachable.

Ripening, Pests and Wildlife-Friendly Care

In late August or early September, pinch out the growing tip of each cordon two trusses above the last set fruit. Energy then goes into swelling and ripening what is already there rather than into new flowers that will never mature. Gradually remove leaves below the lowest truss to improve airflow and reduce the chance of blight. Keep an eye out for brown patches on leaves and stems, and bin affected material rather than composting it.

Deal with pests without reaching for a spray, which would undo all the good your flowers have done. A firm jet of water knocks aphids back; ladybirds, hoverflies and parasitic wasps will finish the job if you leave them somewhere to live. Slugs and snails are best dealt with by an evening torchlit patrol, or by a beer trap sunk into the border. A shallow dish of water and a few seedheads left standing will keep birds and hedgehogs visiting, and they will happily hoover up the next generation of pests for you.

Pick fruit as soon as it colours, when it is warm from the wall and smells of the plant. Any green tomatoes left at the end of the season will ripen on a sunny windowsill, and the very last handful makes a fine chutney. A couple of well-chosen pots, watered reliably and tucked into the warmest corner of the garden, will keep you in tomatoes from July until the first frosts.