Lesson 1. Why overwatering is worse than drought

The most common way to kill a houseplant is to water it too often out of love. It sounds paradoxical: how can too much water kill? It's all about the roots. Roots need not only water but also air (oxygen). In normal soil there are air-filled pores between the particles. When you water, the water pushes the air out, but then the excess drains away, the soil dries a little, and the pores fill with air again — the roots “breathe.” If you water too often, the soil stays wet all the time, the pores are flooded, and the roots suffocate. Suffocated roots die and begin to rot. Rot-causing fungi and bacteria settle on the dying roots, the rot spreads upward — and the plant dies. This is root rot, the main cause of death in houseplants. The treacherous part is that from the outside, overwatering first looks like drought: the leaves wilt, turn yellow and droop. The owner decides “it's thirsty” and waters again — finishing the plant off for good.

Most houseplants have a far bigger margin of safety against drought than against overwatering. An underwatered plant droops and drops some leaves — but the roots are alive, and after watering it usually recovers quickly. Roots that have rotted from overwatering, though, can't be brought back: they're gone. Hence the beginner's practical rule: if in doubt whether to water, DON'T — wait. Better to underwater a little than to overwater. This applies above all to succulents, cacti, snake plants and ZZ plants: they're adapted to drought, and frequent watering kills them fastest of all. There are exceptions. Some moisture-loving plants (bog plants, for example, or ferns and cyperus, the umbrella plant) don't like drying out. But even they don't need “a permanent swampy soup” — they need moist but breathable soil and excess water that always drains away.