Why good drainage matters.

Walk into almost any nursery and someone will tell you to put a layer of gravel or broken pot pieces at the bottom of the planter 'for drainage'. It is one of the most repeated pieces of gardening advice in India, and it is wrong. On the balconies we visit, a layer of stones at the bottom is one of the commonest reasons a healthy-looking plant rots from the roots up. The fix costs almost nothing, and it starts with understanding where water actually sits in a pot.

Why gravel makes it worse

Water does not drain freely out of fine soil into coarse gravel. It clings to the fine particles and only crosses into the bigger gaps below once the soil above is completely saturated. The result is a band of waterlogged soil sitting just above the stones, which growers call a perched water table. Adding gravel does not remove that wet band. It simply lifts it higher up the pot, closer to the roots, and takes away several inches of usable root space at the same time.

In a 10-inch pot with three inches of gravel, the plant is left with seven inches of soil, and the bottom two or three of those stay soggy for days after each watering. Roots that grow into that zone run short of air and begin to rot. Above ground you see yellowing lower leaves, a sour smell from the soil, and a plant that droops even though the pot feels wet. Most people read that droop as thirst and water again.

Use a gritty mix, top to bottom

Drainage is a property of the whole mix, not the bottom layer. Fill the pot top to bottom with one consistent, open mix and water moves evenly through it and out. For most balcony plants we use roughly equal parts cocopeat, good compost and a coarse material such as perlite, pumice or brick grit, with some garden soil added for heavier plants that need anchoring. Squeeze a handful after watering. It should hold together loosely and crumble when you poke it, never ooze.

Plain red garden soil on its own is the other trap. In a pot it packs down within a season, especially under a hose, and behaves much like the wet band above gravel, only throughout the whole pot. If you are reusing old soil, break it up, sieve out the dead roots and mix it back in at no more than a third of the total.

If you want something over the drainage hole, use a square of plastic mesh or old shade net. It keeps the soil in and lets the water out, which is all the hole needs.

Lift the pot and clear the holes

A pot standing flat on a tiled floor often seals its own hole, especially once a film of soil and algae builds up underneath. Three pot feet, or even three small tiles, lift it half an inch and let the water leave. Check the holes every time you repot and once before the monsoon by pushing a skewer up through each one. Nursery pots and cheap ceramic planters sometimes come with a single hole that is too small, or a half-punched one that was never opened at all.

Saucers and the flat below

Saucers are where drainage meets society rules. Most apartment associations hear about it quickly when water drips onto the balcony below, and a dripping planter is one of the usual reasons for a complaint from a downstairs neighbour. Use a saucer wider than the pot, with a proper lip. Water slowly, stop when the first trickle appears in the saucer, and tip it out after half an hour. A saucer left full recreates the same soggy base you were trying to avoid.

For railing planters and anything above a neighbour's window, a lined trough or a planter with a sealed reservoir is the tidier choice. Whatever the container, the rule stays the same: water should move through the pot and out, and nothing should stand at the bottom. Get that right and most of the mystery root problems we are called to look at simply do not happen.

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