Water: the finger rule, and why more plants drown than go thirsty
Almost every plant that dies indoors dies of too much water, not too little. How to water by judgement rather than by calendar, and why drainage matters more than frequency.
Almost every plant that dies indoors dies of too much water, not too little. It is a counter-intuitive fact: we water to take care, and the more we care the more we water. But roots breathe, and in a permanently soaked substrate there is no air: the roots suffocate, they rot, and at that point the plant cannot drink even with the pot full of water. The cruel paradox is that a drowned plant shows limp yellow leaves — the same symptoms as thirst — and the instinctive response is to water again.
The finger rule, worth more than any calendar
Before watering, push a finger into the substrate to the second knuckle. If it feels damp, you wait. If it feels dry, you water. It sounds trivial, but it replaces every "once a week" you have read somewhere: the same plant drinks twice as much in summer as in winter, and next to a radiator it dries in three days what elsewhere lasts a week. The finger reads reality; the calendar does not.
How to water, when you do
Water generously, until it runs from the holes at the bottom, then let it drain completely. Soaking through and letting it dry pushes the roots to explore the whole pot; a little and often keeps only the surface damp and grows lazy roots. Empty the saucer ten minutes later: a plant left with its feet in water is a plant you are slowly drowning.
Drainage matters more than frequency
A substrate that holds too much, or a pot without holes, turns every watering into a risk. That is why my mixes are full of perlite and bark: they create air pockets that let you water thoroughly without suffocating the roots. A good substrate forgives one watering too many; a compacted one does not.
The right water
The lime in tap water, on the more delicate species like Begonia and Sonerila, leaves marks on the leaves and hardens the substrate over time. Use rainwater or demineralised water if you can, or at least let tap water stand overnight. And use it at room temperature: cold water on tropical roots is a shock.
One method that reduces mistakes is bottom watering: you stand the pot in a tray with a few centimetres of water and let the substrate draw it up, ten to fifteen minutes, until the surface turns damp. It is what I use for Begonias, which hate water on their leaves. It wets evenly and never leaves standing water.
If you do overdo it — and everyone does — the remedy is not more water: take the plant out of the pot, check the roots (healthy ones are firm and pale, rotten ones soft and dark), cut the rot away with a clean blade and repot into barely damp substrate, then keep the plant dry for a few days. When in doubt between watering and waiting, wait: thirst is undone in an hour, drowning sometimes is not undone at all.