How can drainage problems cause plant roots to lack air?

In the context of gardening, drainage is essential because plant roots require both water and air to survive. When soil is poorly drained or waterlogged, the pore spaces that typically contain air become saturated with water.12

Because water moves much more slowly than air through soil, these saturated conditions prevent the necessary oxygen from reaching the root zone. This creates an anaerobic, or oxygen-depleted, environment. When roots are forced to exist in these conditions, they effectively drown, as they are unable to access the oxygen required for their metabolic processes. In such environments, anaerobic bacteria may thrive, further altering the soil chemistry and potentially hindering plant health. To prevent this, gardeners often use techniques like installing buried piping or digging sumps—holes filled with stones—to facilitate the movement of excess water away from the root zone.21