Anoxia is a complete absence of oxygen in a soil, water, or root environment. In gardening and plant care, it most often occurs when soil stays saturated for long periods and air spaces around roots fill with water instead of oxygen.
Plant roots require oxygen for respiration, the process that produces energy for nutrient uptake and growth. Under anoxic conditions, roots begin to die, beneficial aerobic microbes decline, and anaerobic microbes increase. This can lead to root rot, foul-smelling soil, reduced nutrient availability, leaf yellowing, wilting despite wet soil, and eventual plant death.
Anoxia is more severe than hypoxia, which refers to low oxygen rather than no oxygen. Heavy clay soils, compacted beds, poorly drained containers, and overwatering are common causes.
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