Your Balcony Is a Real Growing Space

Anyone who has watched a tomato plant sulk through a gale knows that balconies are not simply small gardens. They are their own climate: windier than the street below, often warmer by day because of brick and glass, colder by night because heat escapes upward, and frequently drier than the ground-level border because the balcony above intercepts the rain. Treat that microclimate as a set of problems to solve and the space stops being a compromise. Treat it as an ordinary garden and you will spend the summer watching things snap off in June.

The good news is that the very constraints which make balconies awkward — cramped floor area, no soil, exposure — reward precisely the kind of growing that pays back best: herbs, salads, climbing crops and a few well-chosen fruiting plants in containers you never have to shift.

Read the Site Before You Buy Anything

Spend a fortnight watching before spending a penny. Note the following:

• Sun hours. Six or more hours of direct summer sun suits tomatoes, beans and courgettes. Three or four hours means salads, herbs, chard, radishes and most soft fruit will do better.
• Wind direction. Which way does the prevailing wind hit, and does a neighbouring wall funnel it? A corner can double the speed.
• Rain shadow. Stand outside during a shower. If the paving stays dry, everything you grow will depend on you and the watering can.
• Weight. Wet compost weighs roughly the same as a bag of sand of the same volume, so a large trough can reach 40–60kg. Keep the heaviest containers against the wall or over a supporting beam, never out at the cantilevered edge.
• Services. How far is the nearest tap? A balcony two flights from a water butt is a different proposition from one with a tap on the wall.

Planters That Stay Put

Light, unfixed pots and a gusty third floor are a poor combination. Fix things down. Timber or galvanised troughs bolted to the wall with proper masonry fixings, or brackets clamped to a sturdy railing, will survive weather that sends plastic pots skating across the tiles. If drilling is not possible, use long, heavy troughs set low and weigh them with bricks or a layer of gravel beneath the compost — the wider the base, the more stable the whole thing is.

Whatever you choose, drainage matters more than style. Check for holes, raise containers on pot feet or battens so water escapes instead of pooling, and add a gravel layer only if the design calls for it, since modern multipurpose composts drain well enough on their own. Self-watering troughs with a reservoir earn their keep in a windy, rain-shadowed spot; they buy you a day or two of grace in July.

Compost That Doesn't Sink the Balcony

Weight is the quiet limit on what a balcony can carry, and compost is where most of it hides. A peat-free multipurpose compost lightened with 20–30 per cent perlite or vermiculite holds moisture without turning into a sodden brick, and it drains fast enough to keep roots healthy after a downpour. Coir-based mixes are light and excellent for salads and herbs, though they dry out quickly and need more frequent feeding.

Because container composts are free-draining and plants are watered constantly, nutrients leach away within weeks. Plan to feed: a liquid tomato feed for fruiting crops once flowers set, a general-purpose feed for leafy ones, and a top-dressing of fresh compost in midsummer to replace what has washed through. Refresh the top five centimetres each spring rather than emptying everything out.

Crops That Earn Their Space

Vertical is the only direction a balcony has to spare. Climbing and French beans are the standout performers: sow Cobra or Blue Lake in late May and they will scramble up a cane wigwam or a simple net fixed to the wall, cropping for weeks. Mangetout peas do the same job earlier in the season, and a single tomato plant in a 30-litre pot, trained up a string, will give you more fruit than you expect.

Fill the gaps with crops that crop hard and fast:

• Cut-and-come-again salad in shallow troughs, sown little and often.
• Herbs — rosemary, thyme, sage and mint, the last kept in its own pot, shrug off wind far better than basil.
• Chard and kale for a long season of leaves, even in part shade.
• Strawberries in a railing trough, where the fruit hangs clear of the soil.
• Radishes and spring onions as quick fillers between slower plants.

Watering, Feeding and the Daily Round

In a windy spot sheltered from rain, expect to water daily from June and twice a day during a heatwave. Mulch the surface with a centimetre of compost or gravel to slow evaporation, group pots together so they shade one another, and water in the evening or early morning rather than at noon. A cheap moisture meter takes the guesswork out of it, and a folded windscreen shade wrapped around a tomato pot on a scorching afternoon does more good than any gadget.

Once you have the rhythm, a balcony becomes genuinely productive — a handful of beans, a bowl of salad and a sprig of thyme picked twenty steps from the kettle. That is no compromise on a garden. On a good evening, with the beans climbing and the tomatoes ripening against the wall, it is the best seat in the house.