Water lilies are a commonly-grown hydrophyte in backyard ponds. Source: Wikipedia CC Attribution-ShareAlike 3.0
Honey locust is tolerant of poorly-drained soils. Photo credit: geneva_wirth Flickr CC BY-NC 2.0
Adequate soil drainage is critical for good plant growth. Some plants such as hydrophytes, or water-loving plants, are physiologically adapted to thrive in saturated Hydrophytes have extensive air channels that allow gases to move freely through the plant. Most garden and landscape plants do not fit into this category.
Poor soil drainage will result in water-logged, saturated soils, which greatly affects plant growth. Saturated soils reduce oxygen-availability to roots, and decrease the plant’s ability to take up water through its roots. Plant resistance to pathogens is also inhibited in water-logged soils.
Soils are composed combinations of sands, silts, and clays. Sand is the coarsest of the soil textures, clay is the finest of the soil textures, and silt lies in between sand and clay. Soils that contain similar portions of sands, silts, and clays are termed loams, and plants grow well in loamy soils.
Very sandy soils may be excessively drained which is problematic in that the soil does not hold enough plant-available water. However, clayey soils hold water so tightly that is difficult for plants to extract the water; clayey soils become saturated very easily as they do not drain well. Soils composed of fine silts or silts and clays may also be poorly drained.
Compaction layers, such as those caused by heavy equipment, will cause drainage problems, as will high water tables and shallow bedrock.
Some landscape and garden plants such as willows, arborvitae, and honey locust that tolerate poorly drained soils better than others. Soil conditioners, such as organic matter can be added to soil to improve drainage (note that organic matter will also improve the water holding capacity of coarse-textured soils).
Organic matter is the single-most important soil amendment and should be incorporated as deep as possible. Besides addition of organic matter, there are also other ways to address soil drainage problems: