Gardening glossary
Overwatering
Overwatering is the single most common reason houseplants die, but the name is misleading. The damage is not from the volume of water in any one watering — it is from soil that never gets a chance to dry. Roots need oxygen as much as they need moisture. When pore spaces in the substrate stay full of water for days, roots suffocate, beneficial microbes die off, and opportunistic pathogens like *Pythium* and *Phytophthora* move in. That is root rot.
Tell-tale signs:
- Lower leaves turning yellow, soft, and dropping - Mushy, brown, foul-smelling roots - Wilting **even though** the soil is wet (rotten roots cannot absorb water) - Persistent fungus gnats hovering around the pot - Mould or algae on the soil surface
Common causes:
1. **Watering on a fixed schedule** instead of checking the soil. 2. **Pots without drainage** or cache-pots that pool water. 3. **Oversized pots** holding more substrate than the roots can drink. 4. **Dense, peat-heavy mixes** that compact and stay sodden. 5. **Cool, low-light conditions** where transpiration is slow.
The fix is not "let it dry out and hope" — by the time symptoms show, roots are usually already damaged. Unpot the plant, rinse the root ball, cut away any black or mushy roots with sterile scissors, and repot into a smaller container with fresh, chunky, well-draining mix. Skip fertiliser until new growth appears.
To prevent it, switch to soak-and-drain watering, use terracotta for thirsty species and a moisture meter for the rest, and always check the top 2–3 cm of soil before reaching for the watering can.