Root rot

Updated June 2026

Worst in cool, wet, poorly drained conditions through autumn, winter and early spring, April to September.

Root rot covers a group of soil fungi, including phytophthora and pythium, that attack roots in waterlogged or poorly drained soil. Plants wilt and yellow despite wet soil, and by the time it shows above ground the roots are already mushy and brown, so prevention through drainage is key.

How to identify

• Plants wilting and yellowing even though the soil is wet
• Stunted growth and dieback that does not respond to watering
• Soft, brown or black mushy roots instead of firm white ones
• Sudden collapse of seedlings and young plants in soggy beds

How to prevent

• Improve drainage with raised beds and plenty of compost
• Avoid overwatering and let the surface dry between waterings
• Do not plant into cold, waterlogged soil
• Rotate crops and choose resistant rootstocks and varieties where available

How to control organically

• Pull out and dispose of collapsed plants along with the soil around the roots
• Stop watering and improve drainage before replanting
• Drench seedlings and at-risk plants with a seaweed tonic to strengthen roots
• Solarise or rest badly affected beds before replanting susceptible crops
• Add compost and biology to build soils that suppress root-rot fungi