Start With a Realistic Measure of What You Have

Before you buy a single pot, spend ten minutes out there with a tape measure and a notebook. Narrow urban balconies are usually between 80cm and 120cm deep, and once you account for the door swing, you may only have 60cm of genuinely usable floor. Measure the width of your railing too, and note whether it is a flat-top metal rail, a glass panel or a wrought-iron design with gaps. This determines which brackets and planters will actually grip safely.

Check the aspect while you are at it. A south-facing balcony in Manchester will bake in summer and dry out compost in a day, while a north-facing one in Edinburgh will stay cool and shady, suiting foliage and mint far better than tomatoes. Also look at the wind. Anything above the second floor funnels breezes along the balcony, so tall, top-heavy plants will topple unless you weight the pots or tie stems to the railing.

Finally, know your weight limit. Most residential balconies handle a reasonable load, but saturated compost is heavy, so cluster larger pots near the wall where the structure is strongest rather than along the outer edge.

Use the Railing as Your First Growing Tier

The railing is the most underused surface on a small balcony, and it costs you no floor space at all. Adjustable bracket planters that clamp over the top rail are the simplest option, and they work on most standard widths. Choose trough-style planters of 60cm to 90cm rather than round pots, because a long, shallow run of compost holds more plants and sits more stably.

• Line the inner rail with herbs such as thyme, oregano, sage and chives, which tolerate wind and dry spells better than basil.
• Use the outer rail carefully — trailing plants like nasturtium or ivy-leaved pelargoniums look lovely spilling over, but check they will not drip onto a neighbour's washing below.
• Add a second tier with a double-decker bracket if your railing is sturdy, which effectively doubles your growing area.
• Fix, don't balance. Anything resting loose on a rail will shift in a gust, so use brackets with rubber pads and tighten them properly.

If your railing is glass, clamp-on planters usually will not work. In that case, a slim freestanding shelving unit against the balcony wall does the same job, with the bonus of a little wind protection.

Choose Furniture That Folds Away

A balcony you cannot sit on is just a shelf. The trick is furniture that disappears when not in use. A bistro table with a folding top and two stacking chairs takes up less than half a square metre when folded flat against the wall. Look for powder-coated aluminium or acacia, which cope with damp British weather far better than untreated steel or softwood.

Hang a folding occasional table or a drop-leaf shelf on the wall at seated height — useful for a mug of tea and a pair of secateurs, and it lifts clutter off the floor. If you have a corner, a slim triangular stool or a storage bench doubles as seating and as a home for a trug, a small watering can and a bag of compost. Keep the floor clear wherever possible; that empty strip is what makes a narrow balcony feel generous rather than cramped.

Pick Pots That Earn Their Space

Compact pots are not simply small pots. Deep, narrow containers outperform shallow, wide ones because roots go down rather than spreading, and the compost dries out more slowly. A 25cm-diameter pot with 30cm of depth will grow a healthy bush basil or a compact chilli plant quite happily.

• Square and rectangular pots waste no space between them; round pots always leave awkward gaps.
• Self-watering containers with a built-in reservoir are worth the extra cost on a windy balcony, where evaporation is relentless.
• Terracotta looks warm and traditional but dries out fast; glazed ceramic or good-quality plastic retains moisture better.
• Fill with purpose. Use a peat-free multipurpose compost with added grit or perlite for drainage, and put a layer of crocks or a few stones in the base.
• Group pots together in clusters of three — a tall foliage plant, a mid-height herb and a trailing one — for a fuller look with fewer containers.

Grow Herbs and Foliage That Suit the Space

Herbs are the natural choice for a tiny balcony: productive, fragrant, and perfectly happy in containers. Rosemary, thyme, sage and oregano all prefer a sunny spot and lean, gritty compost. Mint must go in its own pot or it will march through everything else. Parsley, coriander and chives manage in partial shade, which makes them ideal for a north-facing rail.

For foliage structure, consider a small-leaved ivy, a compact heuchera with burgundy or lime leaves, or a box ball in a square pot for a formal touch. If you want flowers as well, choose dwarf varieties of cosmos or a single scented pelargonium, and deadhead regularly to keep them going from June to September.

Keep the Care Routine Simple and Regular

Container plants live on your attention, but the routine need not be a chore. Water in the morning during summer, ideally before the sun reaches the pots, and check the top two centimetres of compost with your finger — if it is dry, water until it runs out of the drainage holes. On hot days a balcony can need watering twice daily, so a small watering can kept on the balcony saves endless trips.

Feed every fortnight from April to September with a general liquid feed, switching to a tomato feed once flowering begins. Trim herbs often, taking the top few centimetres of growth, which keeps them bushy rather than leggy. In autumn, move tender plants inside, empty and clean saucers to prevent waterlogging, and raise pots onto feet so they do not sit in winter rain. A little attention each week will keep your narrow balcony green, useful and genuinely lovely to sit in.