Why Tomatoes Love a Container

Tomatoes are one of the most rewarding crops you can grow, and you do not need a garden to do it. A sunny patio, a balcony with a bit of shelter, or even a spot beside a south-facing wall will do nicely. Containers also give you a level of control that open ground cannot: you choose the compost, you control the watering, and you can move pots under cover when the weather turns.

The catch is that a tomato in a pot is entirely dependent on you. There is no subsoil to draw moisture from and no reserve of nutrients to fall back on. Get two things right — consistent watering and regular feeding — and you will be picking ripe fruit from midsummer well into autumn.

Choosing Bush or Cordon Varieties

Tomatoes fall into two useful groups for container growing.

• Bush (determinate) varieties grow to a set height, usually around 45–60cm, then stop and produce a crop more or less all at once. They need little or no staking and are ideal for hanging baskets, window boxes and smaller pots. Look for compact types with trailing or tumbling habits.
• Cordon (indeterminate) varieties keep growing upwards and cropping until the frosts stop them. They need a cane or string for support and a weekly side-shooting routine, but they give you a longer, heavier harvest.

For a first attempt, plant one of each. A bush type gives you an early confidence boost while a cordon such as 'Gardener's Delight' or 'Moneymaker' keeps fruit coming for months. Cherry varieties are generally more forgiving than large beefsteak types, especially in a wet British summer, because they ripen faster and are less prone to splitting.

If you are growing outdoors, avoid the huge beefsteak varieties. They need a long, hot season that only a greenhouse or a very lucky summer can provide.

Pots, Compost and Planting Up

Size matters more than most beginners expect. A cordon tomato wants a pot of at least 10–15 litres, roughly 30–35cm across. Bush types can manage in 7–10 litres. Terracotta dries out faster than plastic, so if you use it, go up a size or line the inside with a piece of old compost sack.

Use a quality peat-free multipurpose compost, or a soil-based mix if you find peat-free dries out too quickly in your conditions. Add a handful of slow-release fertiliser granules at planting time and mix it through the top 10cm. Never use garden soil on its own — it compacts in pots, drains poorly, and brings in weeds and pests.

Plant deeply, burying the stem up to the first set of true leaves. Tomatoes will throw roots from that buried stem, which makes for a stronger plant. Water in well and keep the pot somewhere bright and sheltered, ideally against a warm wall that will radiate heat back overnight.

Watering: The Make-or-Break Job

Irregular watering is the single biggest cause of disappointing container tomatoes. Let a pot dry out and then flood it, and you invite blossom end rot — the sunken black patch on the base of the fruit — as well as cracked skins and split shoulders.

• Aim for evenly moist, never soggy and never bone dry. Check daily by pushing a finger 2cm into the compost.
• In hot weather, a large pot may need water twice a day. Once in the morning thoroughly beats a light sprinkle at noon.
• A saucer under the pot holds a little reserve, but empty it if water sits there for more than an hour or two.
• A 2cm mulch of grass clippings, bark or wool compost on the surface slows evaporation dramatically.
• Water the compost, not the leaves, to reduce the risk of blight and mould.

Feeding and Supporting as Fruit Swells

Once the first truss of flowers has set and tiny green fruits appear, switch from plain water to a high-potash tomato feed diluted as the instructions suggest. Feed once a week at first, then twice a week once the plant is carrying several trusses. Potash drives fruit development; too much nitrogen at this stage gives you enormous leafy plants and almost nothing to eat.

Support stems before they need it. Push a cane in at planting time, so you are not disturbing roots later, and tie the stem in with soft string in a loose figure of eight. As fruit swells, the weight increases sharply — check ties weekly and add a second cane to heavy croppers.

For cordons, pinch out the side shoots that appear between the stem and each leaf, and remove the growing tip once four or five trusses have set outdoors, or six to seven under cover. Bush varieties need no pinching at all.

Ripening, Problems and Late-Season Care

Ripening slows as light levels drop in September. Thin out some leaves above the trusses to let light in, and stop feeding by early September so the plant concentrates on ripening what it already holds. Any remaining green fruit at the end of the season will ripen indoors on a sunny windowsill, or in a drawer with a ripe banana, which releases ethylene and speeds the process.

Watch for the usual suspects: yellowing lower leaves (often just age or hungry roots), whitefly (encourage ladybirds, or hang a yellow sticky trap), and blight in warm, humid spells. Blight spreads fast — remove and bin affected foliage immediately rather than composting it. Keep picking ripe fruit regularly, as harvesting encourages the plant to keep setting more. There is nothing quite like the smell of a tomato still warm from the plant, and with a decent-sized pot and a watering can in hand, you can be eating your own by August.