Root rot
Several water moulds and fungi, above all Phytophthora and Pythium, rot the roots of plants kept too wet. The plant wilts as if dry, yellows and collapses; roots are brown and mushy and the outer skin slides off.
Fungal diseases
What it looks like
It happens underground, and shows as wilting.
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Wilting in wet soil The plant flags although the soil is wet. -
Yellow leaves Leaves yellow and drop. -
Brown, mushy roots Roots are dark and soft; the outer layer sloughs off. -
Dark stem base The stem darkens at soil level.
How to confirm it
Check the roots.
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Slide the plant out
Healthy roots are white and firm; rotting ones brown and soft.
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Smell
A sour, rotting smell from the compost.
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Wet soil
Soil stays wet for days.
What to do
Save what you can.
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Cut away rot
Trim soft roots back to firm, healthy tissue.
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Repot
Repot in fresh, free-draining compost in a clean pot.
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Water less
Let the compost dry more between waterings.
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Replace in the ground
In the garden, remove the dead plant and improve drainage before replanting.
Prevent it next time
- Plant in free-draining soil or raised beds.
- Use pots with holes.
- Water by the soil, not the calendar.
What not to do
Do not replant the same kind of plant in the same wet spot.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Phytophthora root rot, Royal Horticultural Society