Root Rot in Houseplants
Root rot is the most common disease seen in indoor plants, and it's very often the result of overwatering. The tricky part: the above-ground signs look a lot like underwatering, so plenty of people water a rotting plant even more. Learning to check the roots is the key to saving it.
What root rot is
Root rot is caused by soil-borne fungi and fungus-like organisms — commonly Pythium, Phytophthora, Rhizoctonia, and Fusarium. These pathogens thrive in wet, poorly drained potting soil and attack the roots of stressed or weakened plants. Healthy roots are firm and white; rotted roots are mushy, and brown or reddish, and may smell bad.
Likely causes
1. Overwatering
The most common trigger. Constantly wet soil starves roots of oxygen and invites the fungi that cause rot. Fix: Water only when the soil needs it, not on a schedule. Let the top of the soil dry out between waterings.
2. Poor drainage / no drainage holes
If the pot can't drain or the soil is heavy and waterlogged, the roots sit in water. Fix: Use a pot with drainage holes and a free-draining potting mix. Don't let the pot sit in a saucer of standing water.
3. Garden soil instead of potting mix
Soil from the garden can carry root-rot fungi and drains poorly. Fix: Use a pasteurized commercial potting mix, not garden soil.
The signs
- Wilting that starts on the lower leaves and can move up the plant.
- Leaves that yellow or drop.
- When you take the plant out of the pot, the roots are brown, mushy, and soft instead of firm and white — and they may smell bad.
- The soil stays wet for a long time after watering.
Because wilting can mean "too dry," always check the soil moisture and the roots before adding more water.
How to fix it
1. Stop watering and let the soil dry out. 2. Check the roots: take the plant out and look. If most roots are mush, the plant may be best thrown out (it's the most cost-effective option for badly rotted plants). 3. If you want to keep it, reduce soil moisture, repot what's left into fresh, well-draining mix in a pot with drainage holes, and don't overwater again. 4. Don't reuse the old potting mix or let the plant sit in drained water.
Prevention — well-draining soil, drainage holes, and watering only when needed — is far easier than a cure.
Preventing root rot
Root rot is almost always preventable. Use a pot with drainage holes and a free-draining potting mix, never let the plant sit in standing water, and water only when the soil actually needs it — test with your finger rather than following a calendar. Repot root-crowded plants into a slightly larger container before they become stressed, and don't reuse old, possibly contaminated potting mix. A healthy plant that's watered properly but not overwatered is far less likely to develop root rot in the first place.
Related plants
- Pothos — root rot from overwatering is its main problem
- Snake plant — the quickest way to kill one is overwatering
- ZZ plant — rots if kept wet