Choosing the right pot size and drainage for balcony containers

Most people pick a pot because they like the look of it, then go hunting for a plant to fit. That order is backwards, and it explains a lot of the dead balcony plants we hear about: roots rotting away in something too big, or a plant sulking for months in something too small. Sort the container out first. A surprising number of other problems never even show up.

Size the pot to the plant, not the other way round

A decent rule of thumb for a seedling: the pot should be roughly 2 inches wider than the root ball. When you're moving a mature plant into a bigger home, don't go more than 4–6 inches wider than its current pot. Go bigger than that and the extra soil holds onto water the roots aren't ready to use yet, which is probably the biggest single cause of root rot on balconies.

• Seedlings and herbs: 6–8 inch diameter pots
• Mid-size plants (marigold, curry leaf as a young plant): 10–12 inch pots
• Small trees or shrubs in containers: 16 inch+ pots, and expect to repot every 1–2 years

Drainage holes are not optional

A pot with no drainage holes will waterlog sooner or later, however carefully you water it. Fallen for a pretty pot with a sealed base anyway? Drill 3–4 holes, about 1 cm each, into the bottom. Or skip the drilling and use it purely as a decorative outer shell, with the actual plant sitting in a properly drained nursery pot inside.

Protecting the floor underneath

This is the bit that's particular to apartment life. Drainage water that soil soaks up without complaint will happily stain a balcony tile, and given enough time it can seep into the floor slab underneath. Use a saucer under every pot, but only if you actually empty it after watering; a saucer that's left full just becomes a second container the roots are sitting in. Raising pots slightly on pot feet or a couple of bricks helps air move under the base and slows staining. For railing planters, always fit the matching drip tray — runoff dripping straight onto the balcony below is one of the more common sources of society complaints in high-rises.

On materials, briefly: terracotta breathes and dries fast, which forgives you if you tend to overwater, but it's heavy and chips if you knock it. Plastic holds moisture longer and suits hot, dry corners where things dry out too quickly anyway. Grow bags are cheap, drain well without any fuss, and are the easiest option to shift around if you're renting and might be moving the whole setup next year.