A Moist F Mull develops at sites characterised by continuously or periodically wet conditions if the soil is at least periodically water-saturated up to the surface, which is indicated by the occurrence of specific plants and on soils with a low-to-high base saturation and moderately-to-readily decomposable litter. The thickness of the hydromorphic A horizon is generally 10–20 cm, with an organic carbon content of 4–8% mass. The distinct features are:
- Owl horizon is present almost all year round;
- Owf horizon is present; and
- hydromorphic features in the A horizon.