It sounds counterintuitive, but plants can look wilted in waterlogged soil. That’s because roots don’t just need water — they need oxygen.
RHS explains the core mechanism clearly:
- waterlogging limits oxygen supply to roots
prevents carbon dioxide from diffusing away
root function is reduced or stops
roots begin to die off, enabling rots and decay organisms
What happens inside the soil
When soil stays saturated:
air spaces fill with water
oxygen is depleted
roots can’t respire normally
the plant can’t absorb water/nutrients properly
RHS also notes wet soils can increase risk of root diseases like Phytophthora in some situations.
Symptoms you’ll actually see in the garden
yellowing leaves
weak growth
dieback from tips
sudden collapse after heavy rain
plants failing repeatedly in the same area
Why Mediterranean plants often fail first
Plants adapted to free-draining conditions can be intolerant of winter waterlogging; RHS has even funded research into waterlogging effects on Mediterranean species.
How to fix it
Improve surface runoff
Add organic matter where appropriate
Use targeted drainage solutions for persistent areas
Choose plants suited to wet soils where drainage can’t be improved easily