Soils that are wet frequently enough to periodically produce anaerobic conditions, thereby influencing the species composition or growth, or both, of plants on those soils.

Soils types characterized by their considerable moisture content.

Soils that are saturated, flooded, or ponded long enough during the growing season to develop anoxic conditions in the upper part of the soil profile.

Undrained clay-like soils.

Soils that are saturated with water at or near the surface and are oxygen-deficient long enough to disrupt the growing season.

Soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part.

Soils that have developed in wet, flooded, moist, or saturated conditions. Hydric soils tend to have a heavy clay content.

Soil that is saturated or flooded long enough during the growing season to develop conditions which are indicative of wetlands.