Root rot is one of the most common reasons plants decline and die — and because it happens underground, it is often spotted too late. This guide explains what root rot is, how to recognise it early, what to do when you suspect it, and how to prevent it. Treatment varies by plant and severity, so there is no single fix that works for every plant — use this as a framework, and adjust to the plant in front of you.
What root rot is
Root rot is the decay of a plant’s roots, usually caused by roots sitting in waterlogged, low-oxygen conditions where soil-borne fungi and water moulds thrive. Healthy roots are firm and pale; rotting roots turn brown or black, soft and mushy, and can no longer take up water and nutrients — which is why a plant with root rot often looks thirsty even in wet soil.
Common causes
- Overwatering — watering too often so the mix never dries enough for roots to breathe.
- Poor drainage — a pot with no drainage hole, a saucer left full of water, or heavy soil that holds water.
- The two combined — frequent watering in a poorly draining pot is the classic setup for rot.
- Compacted or broken-down potting mix that no longer holds air.
Overwatering vs poor drainage: they produce the same result (airless, saturated roots) but the fix differs — overwatering is a habit to change; poor drainage is a pot/soil problem to correct. Often you need to address both.
Early symptoms
- Wilting or drooping despite moist or wet soil.
- Yellowing lower leaves; slowed or stalled growth.
- Soil that stays wet for a long time and may smell sour or musty.
Root symptoms (on inspection)
- Brown, grey or black roots that are soft, slimy or mushy.
- Roots whose outer layer slips off leaving a thin thread.
- A rotten, swampy smell. Healthy roots, by contrast, are firm and light-coloured.
Above-ground symptoms
- General decline: wilting, yellowing, leaf drop, dieback of stems.
- A plant that doesn’t recover after watering (because the roots can’t take water up).
What to do when you suspect root rot
- Stop watering and check the roots — ease the plant out of its pot and inspect.
- Assess the damage. If most roots are still firm and pale, recovery is likely; if the whole root ball is mush, it may be too far gone.
- Remove damaged roots where appropriate — trim off the soft, blackened roots with clean, sterilised tools, keeping the healthy firm roots. Sterilise blades between cuts and between plants.
- Repot into fresh, well-draining medium where appropriate — discard the old sodden mix, use a clean pot with drainage, and don’t reuse contaminated soil. See soil & growing media and how to choose a pot.
- Improve drainage — ensure drainage holes are clear, never leave the pot in standing water, and choose a mix and pot suited to the plant.
- Ease off afterwards — water sparingly until new growth shows the plant is recovering.
Chemical fungicides are not a general cure for root rot and are only relevant in specific situations for specific plants — fixing the water/air balance at the roots is what matters most.
Container vs in-ground
- Containers: the most fixable case — you control the pot, the mix and the watering. Repotting into fresh well-draining medium with proper drainage usually gives the best chance.
- In-ground: harder, because you can’t swap the soil. Improve the site’s drainage (raised beds/mounds, adding organic matter, avoiding low spots that pool water) and reduce supplemental watering. Prevention matters more here.
Prevention
- Water based on the plant’s needs and the soil’s dryness — not on a fixed schedule.
- Always use pots with drainage holes; empty saucers after watering.
- Match the potting mix to the plant (free-draining for plants that resent wet feet); refresh tired mix.
- Don’t overpot — a huge pot holds a lot of unused wet soil around small roots.
When recovery is unlikely
If the entire root system is soft and black, the stem base is mushy, or the plant collapses when lifted, recovery is doubtful. For a valued plant you can try taking healthy cuttings or dividing off any surviving firm-rooted section rather than trying to save the rotted parent.
Related guides
- Soil & growing media — well-draining mixes
- Best plant pots & containers — drainage & size
- When & how to repot a plant
- Overwatering vs underwatering – tell them apart and fix each.
- how to choose the right soil
