Start with the Pot, Not the Plant

Most patio vegetable failures come down to the container, not the gardener. A tomato in a 10-litre pot will sulk, set a handful of fruit and give up by August. Give the same plant 30 litres of good compost and it will crop until the first frost. As a rough guide, think in litres rather than inches: salad leaves and herbs will manage in 5–10 litres, bush tomatoes, peppers and chillies want 15–20 litres, and courgettes, aubergines and full-size tomatoes need 25–35 litres. Climbing beans are happiest in a deep pot of at least 30 litres.

Terracotta looks lovely but dries out fast in a sunny corner, so glazed ceramic or good-quality plastic will save you a lot of watering. Whatever you choose, drainage matters more than anything else. Check for holes at the base, and if there is only one, drill a couple more. Stand pots on feet or bricks so water can escape freely, and use saucers only as a temporary measure in high summer – sitting in a puddle rots roots quietly and thoroughly.

Filling Up: Compost, Drainage and Weight

Use a peat-free multi-purpose compost as your base. It holds moisture well and has enough nutrients for the first six weeks or so. For long-term crops such as tomatoes, peppers or courgettes, mix in a couple of handfuls of soil-based compost or well-rotted garden compost to give the mix more body and slow-release goodness. Adding water-retaining granules helps smaller pots enormously, but don't overdo it – a swollen, jelly-like bed is worse than a dry one.

Tall pots and top-heavy plants become unstable once they are full of damp compost. Put a layer of broken polystyrene, gravel or crocks in the bottom third to add weight and improve drainage, and plant into the middle rather than right at the edge. If you are growing on a balcony or roof terrace, check what weight the surface can take before filling twenty pots with wet compost – it is surprisingly heavy.

The Crops That Earn Their Space

Patios suit compact, productive, cut-and-come-again crops. These are the ones I would plant without hesitation:

• Bush tomatoes such as 'Tumbling Tom' or 'Red Alert' – no staking, heavy cropping, happy in a 20-litre pot.
• Salad leaves – rocket, mizuna and loose-leaf lettuce sown little and often, cropping in three to four weeks.
• Radishes – the fastest reward on the patio, ready in under a month from a sowing in a shallow trough.
• Courgettes – one plant per 30-litre pot will feed a household if you keep picking.
• Runner and French beans – dwarf French beans need no support; runners want a wigwam of canes and a sheltered spot.
• Chard and kale – excellent for autumn and winter picking, and far less bothered by pests than cabbage.
• Herbs – basil, parsley, mint, thyme and chives. Keep mint in its own pot or it will colonise everything else.

Skip maincrop potatoes, sweetcorn and big brassicas. They need space, time and ground you simply do not have in a pot.

Watering and Feeding Through the Season

Container compost dries out far faster than a border, and a plant that wilts repeatedly will never crop properly. Water in the morning if you can, so the roots have moisture before the heat of the day, and check pots again in the evening during July and August. Push a finger in to the second knuckle – if it is dry, water until it runs out of the base. Little and often is the enemy here; a thorough soak every day or two suits most plants better than a daily sprinkle.

Feeding starts once the compost's own nutrients run out. From about six weeks after planting, give a liquid feed every fortnight, switching to a high-potash tomato feed once flowers appear. Leafy crops prefer a nitrogen-rich feed; fruiting crops want potash. In mid-summer, a seaweed-based tonic every couple of weeks keeps plants resilient through heat and pest pressure.

Keeping Pests and Weather at Bay

Containers are vulnerable because pests find them easily and there is nowhere for plants to hide. Slugs and snails are the main offenders – go out with a torch after dark, or ring pots with copper tape and keep the area around them clear of damp hiding places. Vine weevil grubs hollow out compost and kill plants from below; if a plant collapses for no clear reason, tip it out and inspect the roots.

Cabbage white butterflies will find any brassica, so cover pots with fine mesh or fleece from the moment you plant. Aphids cluster on soft new growth – squash them by hand or blast them off with a hose before they multiply. A few marigolds or nasturtiums among the pots bring in beneficial insects and draw aphids away from your crops.

Finally, watch the weather. Wind dries compost and snaps stems, so move tall plants against a wall or tie them in. In a heatwave, group pots together to shade one another, and mulch the surface with a layer of gravel or grass clippings to slow evaporation. A sheet of fleece thrown over tender plants on a cold May night costs nothing and saves everything.