A balcony is a microclimate, not a small garden
Plants that shrug off a summer in the ground struggle four floors up. Wind accelerates around buildings and strips moisture from leaves; masonry and glass radiate heat long after sunset; and a container holds a tiny reservoir of soil that swings from soaked to bone dry in a single afternoon. Working with those conditions instead of against them is the difference between a balcony that looks good in June and one that still looks good in September.
Bigger pots solve most problems
The single most effective upgrade is volume. A 30-litre planter holds enough soil to buffer temperature and moisture through a heatwave; a 5-litre pot in the same spot may need water twice a day. Prefer wide, deep containers with real drainage, and group them so they shade each other’s sides. Light-coloured glazed ceramic and thick plastic stay cooler than dark metal, which can cook roots against a sunny wall. Terracotta is beautiful and breathable but dries fast — reserve it for herbs and Mediterranean plants that like it that way.
Anchor everything before the first storm
Wind is the hazard people underestimate. Tall plants act as sails, and a toppled pot from a railing is a serious matter. Keep heavy containers on the floor along the wall, use proper railing planters with metal brackets rather than hooks, and stake anything above knee height with bamboo and soft ties. A trellis or a slatted screen on the windward side cuts gusts dramatically and creates a calmer pocket where more delicate plants can sit. Check ties monthly as stems thicken. If your building allows it, a length of shade cloth stretched across the sunniest corner for July and August lowers leaf temperature enough to keep tomatoes setting fruit through a heatwave, and it comes down again in September.
Water deeply, early, and add reserves
Shallow evening sprinkles encourage surface roots and invite fungal problems. Water in the morning, slowly, until it runs from the base, and let the mix dry slightly before repeating. Self-watering planters with a reservoir genuinely earn their price on a hot balcony, as do watering globes for smaller pots and a simple drip kit on a tap timer if you travel. A two-centimetre mulch of bark or gravel on the soil surface cuts evaporation substantially and stops the mix crusting over.
Choose plants that like the conditions you have
For a hot, exposed south-facing balcony: rosemary, thyme, lavender, pelargoniums, sedum and ornamental grasses take glare and wind without complaint. For a shaded or north-facing one: ferns, heuchera, hostas, fuchsia and mint do far better than sun-loving annuals that will simply sulk. Cherry tomatoes, chillies and bush beans crop well in large containers with six hours of direct sun and steady feeding. Resist the temptation to buy whatever looks good at the shop — measure your hours of direct sun first, then shop. Photograph the balcony at three points across a single day and count the hours the sun actually lands on the floor rather than the railing; most people overestimate by half.
Feed more, and edit through the season
Frequent watering flushes nutrients out of containers quickly, so balcony plants need feeding roughly every two weeks through the growing season, or a slow-release granule mixed in at planting. Deadhead flowering plants weekly to keep them producing, pinch herbs to stop them bolting, and pull anything that has clearly given up rather than nursing it into autumn. A balcony has limited space, and the ruthless gardener has the better view.