Why Tomatoes Love a Sunny Patio

If you only have a paved yard, a balcony or a strip of concrete outside the back door, tomatoes are still well within reach. In fact, a south- or west-facing wall can be the warmest spot on the whole property — a sun trap that ripens fruit weeks ahead of an exposed allotment plot. The key is understanding that a tomato in a pot depends on you entirely for water, food and shelter, so the trick is to set things up properly at the start rather than improvising in July.

Container growing suits smaller, determinate (bush) varieties best, though cordon types will crop happily if you keep on top of watering and supports. Good starting points include Tumbling Tom for hanging baskets and low pots, Red Alert and Moneymaker for dependable bush cropping, and Gardeners' Delight or Sungold for sweet cherry fruit on cordons. If blight is a recurring problem where you live, seek out resistant varieties, as outdoor plants in a damp August are especially vulnerable.

Choosing the Right Pot and Compost

Size matters far more than most beginners expect. A tomato plant in a 5-litre pot will sulk, dry out and give you a handful of small fruit; the same plant in a 20-litre pot will crop generously. As a rule:

• Bush and cherry varieties: at least 10–15 litres per plant, roughly a 30cm pot.
• Cordon varieties: 20–30 litres, so a 35–40cm pot or a grow bag of similar volume.
• One plant per pot, unless you are using a proper grow bag and spacing two along it.

Terracotta looks lovely but dries out quickly; glazed ceramic, plastic or fabric pots hold moisture far better. Whatever you choose, check it has drainage holes and stand pots on feet or bricks so surplus water can escape. A saucer underneath is useful during hot spells but should be emptied after heavy rain, otherwise roots sit in cold, stagnant water.

Use a good-quality peat-free multipurpose compost, ideally mixed roughly half and half with a soil-based compost such as John Innes No. 3. That blend holds moisture and nutrients without compacting into a brick. A handful of slow-release fertiliser stirred in at planting time saves you work later in the season.

Planting Up and Giving Plants Something to Climb

Wait until the risk of frost has passed — late May across most of the UK, early June in the north. Harden plants off over a week, bringing them under cover at night at first. Plant deeply, burying the stem up to the first pair of leaves; tomatoes root along that buried stem and anchor themselves firmly.

Support is not optional. A cordon tomato can easily reach 1.8m, and a plant heavy with trusses will topple a flimsy cane. Push a sturdy bamboo cane, spiral stake or metal frame into the pot at planting time, before the roots fill the space. Tie the stem loosely with soft string or purpose-made ties, adding a new one every 20–30cm as the plant grows. On windy patios, weight the base of the pot with a couple of bricks, or group pots together so they shelter one another.

Watering: The Single Biggest Factor

Inconsistent watering causes more trouble than anything else: split fruit, blossom end rot and leathery skins. Aim to keep the compost evenly moist — never bone dry and never waterlogged.

• Water in the morning where possible, directing it at the compost rather than the leaves. Wet foliage encourages blight and mould.
• In July and August, a large plant in a big pot may need a full watering can every day, sometimes twice on scorching days.
• Push a finger 2cm into the compost before watering; if it is dry at that depth, it is time.
• A thick mulch of grass clippings or garden compost on the surface slows evaporation considerably.

If you are away often, self-watering pots, drip irrigation kits or a simple reservoir made from a plastic bottle sunk into the compost will pay for themselves in saved fruit.

Feeding, Pinching and Keeping Plants Healthy

Start feeding when the first truss of flowers sets fruit, roughly six weeks after planting. Use a high-potassium tomato feed once a week at first, increasing to twice weekly once plants are cropping heavily. Stop feeding in late August so plants concentrate on ripening what is already there.

Cordon varieties need their side shoots pinching out. Look for the small shoots growing in the angle between the main stem and each leaf, and nip them off with thumb and forefinger while they are still tiny. Let the plant carry five or six trusses, then pinch out the growing tip in late summer to stop it producing foliage it cannot hope to ripen. Bush varieties need no pinching and no stopping; just leave them to get on with it.

Watch for greenfly and whitefly on the soft growing tips. A blast of water or a spray of diluted washing-up liquid usually deals with a light infestation, and encouraging ladybirds with nearby flowers helps enormously. Remove any yellowing lower leaves to improve airflow around the plant.

Ripening the Crop and Extending the Season

By late August, remove a few leaves shading the lower trusses so sunlight reaches the fruit. Pick tomatoes as they colour fully — flavour is best from fruit ripened on the plant, though you can finish green fruit on a sunny windowsill indoors.

At the end of the season, any remaining green tomatoes make excellent chutney, or can be ripened in a drawer with a banana. If a hard frost is forecast, lift whole plants and hang them upside down in a shed; the fruit will carry on ripening slowly for weeks. Clean your pots, store them dry, and spend the winter poring over catalogues for next year's varieties. Patio growing is quietly addictive, and there is always room for one more pot.