What is the Permanent Wilting Point (PWP) for plants?

The Permanent Wilting Point (PWP) for plants refers to the soil moisture content at which plants can no longer maintain turgor pressure, leading them to wilt irreversibly if moisture is not replenished. At this stage, the water retained in the soil is insufficient for the plants to absorb and utilize, resulting in a physiological state that prevents normal biological function.

As plants reach this critical moisture level, the roots are unable to extract water effectively due to the high tension in the soil, which means that even though some moisture may still be present, it is not available for use. This point is essential for understanding plant water needs, as surpassing it can threaten plant survival and growth. Knowing the PWP helps horticulturists and landscape professionals manage irrigation effectively and recognize when a plant is under significant stress due to insufficient water availability.