On a sunny balcony you can grow tomatoes, chillies and dwarf French beans in pots. On a shady one, salad leaves, mint and radishes. The two things that decide whether any of it survives are pot size, because small pots dry out by lunchtime while everyone’s at work, and how much weight the balcony can safely carry, because a big pot of wet compost is heavier than it looks. Get those two right and the plants mostly look after themselves between a Sunday feed and a daily can of water.
Everything below assumes a balcony with no tap, so every litre comes through the flat in a can. That shapes most of the decisions.
Before buying anything: weight, wind and which way it faces
The RHS is blunt about the first question, and it’s one I’d never have thought to ask. On roof gardens and balconies their advice is to check “How much weight the roof can take”, because “large containers full of compost and plants weigh a considerable amount”, and to put “Heavy containers … near load-bearing walls or over a load-bearing beam”. On a balcony that means against the wall of the building, not along the outer railing, and it means asking the landlord or managing agent whether there’s a stated limit. A 45cm pot full of wet compost is heavier than you’d want to carry; six of them along the railing put that weight on the part of the structure furthest from any support.
Wind is the second. Balconies above the second floor are windier than any garden, and the RHS says to use “slatted or mesh screens that simply filter the wind” rather than solid ones, which just create turbulence on the other side. A length of willow or reed screen cable-tied to the railing is enough, and it comes down when you leave.
Aspect is the third, and there’s no fixing it. South- and west-facing balconies get afternoon sun and grow fruiting plants. North-facing ones get none and grow leaves. East-facing gets morning sun only, which is somewhere in between. Stand out there at 2pm on a clear day and be honest about which one you’ve got.
Big pots, fewer of them
Pot size is the decision that makes the biggest difference. The RHS guidance for vegetables in containers is to “Aim for containers with a depth and width of at least 45cm (18in), otherwise frequent watering and feeding will be needed”. Frequent, for someone out all day, means dead.
A 45cm pot holds enough compost to stay damp from a morning watering to the evening. A 20cm pot, the size supermarket herbs come in, is dry by noon in June. So three big pots, not ten small ones, and a saucer under every one so the water you do give has somewhere to sit rather than running through onto the neighbour’s balcony.
Big pots are heavy, which is where the weight question comes back. Go plastic or fibre rather than terracotta, stand them on pot feet or a couple of bits of timber so the base drains, and fill them in place. Don’t fill a 45cm pot in the kitchen and then try to carry it out.
Use multipurpose compost, not soil from anywhere, and mix in a handful of slow-release feed granules at planting time. It buys you a few weeks before the liquid feeding routine has to start.
What grows on a sunny balcony
Tomatoes, if there’s sun for most of the afternoon. The RHS tomato guidance is to “Plant one tomato plant in a 30–45cm (12–18in) pot”, plant out “once temperatures are reliably above 16°C (60°F)”, usually late May, and in containers to feed “an organic high potassium liquid fertiliser” every 10 to 14 days once the fruits start swelling. Container tomatoes may need watering daily in hot weather. Buy a bush or tumbling variety, not a cordon, so there’s nothing to tie in or pinch out, and one plant per pot. I didn’t know there were two kinds of tomato plant until I read that page, and it’s the single most useful thing on it.
Chillies are easier than tomatoes: smaller plants, less water, and they sulk less if you miss a day. One plant in a 30cm pot against the warmest wall, fed on the same tomato feed.
Dwarf French beans are the one on the RHS list that people forget. No canes, a 45cm pot takes eight or nine plants around the edge, and they crop for weeks from July if you keep picking.
What I’d skip on a sunny balcony: courgettes, which need a pot the size of a dustbin and more water than a can delivers; anything that needs a cane taller than the railing, because the wind takes it; and strawberries in hanging pots, which dry out faster than anything else.
Photo: Letícia Alvares via Pexels
What grows on a shady one
A north-facing balcony won’t ripen a tomato. It will grow salad, and salad is what you actually buy every week.
Cut-and-come-again salad leaves, sown thinly across the top of a 45cm pot every three weeks from April to August. Cut the outer leaves, leave the middle, and a single pot keeps a household in side salad from May until it bolts. The RHS list of container crops includes salad leaves, radishes, salad onions and herbs, and all of them tolerate shade better than fruit does.
Mint, on its own in a pot, because it takes over anything it shares with. Parsley and chives alongside in another. Radishes, which go from seed to plate in about four weeks and don’t mind the cool. Salad onions, sown in a row and pulled young.
A shady balcony also suits the herbs otherwise bought in plastic: a pot of parsley, chives and mint covers most of what a store-cupboard cooking list needs fresh, and a chilli plant on the sunny side of the door is the rest.
Water and feeding on a working week
There’s no tap. Everything comes through the flat in a watering can, so the routine has to be short or it won’t happen.
Water in the morning before work, every pot, until it runs into the saucer. In a normal week that’s one 10 litre can for three or four big pots. In a heatwave the RHS warns that “in summer, plants often need watering twice a day”, and that’s the week you water again when you get in and accept that the small pots may not make it.
In a shared house, agree who waters before anyone sows anything. A balcony that’s everyone’s tends to be watered by nobody, and a week of that in July is the end of it. On your own, the honest question is what happens when you go away; a neighbour with a key or a saucer full of water buys about two days, not a fortnight.
Feed once a fortnight. The RHS says “A feed of general-purpose liquid fertiliser can be applied every two weeks” for container vegetables, and for tomatoes the high-potassium feed every 10 to 14 days once fruit sets. Fix it to one day, say Sunday morning, with the feed measured into the can, so every pot gets it and there’s nothing to remember.
Keep everything for this in one lidded box: watering can, feed, a scoop, a trowel, string, and the seed packets. In a flat with no shed that box goes under the sink, in the corner that survives the occasional leak from the waste pipe, because compost and feed don’t mind getting damp and the lid keeps the smell in.
Autumn: what to compost, what to bring in, what to leave
By October the tomatoes are done and the beans are yellow. Pull the plants, shake the compost off the roots back into the pot and put the plants in the food waste caddy. The spent compost isn’t good for another fruiting crop, but it’s fine topped up with fresh for next year’s salad, so leave it in the pots over winter with the saucers removed so they drain.
Bring in the chilli, if it looks healthy. On a windowsill it can overwinter and crop earlier next year. Bring in a small pot of the parsley and chives for the kitchen sill.
Leave the mint outside. It dies back, looks dead until April, and then comes back bigger. Leave the screens on the railing; winter is when the wind is worst.
Empty and stack the small pots you’ve stopped using. By the second autumn there’ll be several, and the space they took is where the chair goes. A balcony has the same rule as the rest of a small flat: fewer, bigger things that earn their place.
