What effect does excessive phosphorus have on plants?

Excessive phosphorus in plants can lead to a condition where they develop dark green leaves, which may indicate an abundance of nutrients that are in excess of what the plant needs for optimal growth. In addition, this nutrient overload can result in the plant shedding its older foliage. This phenomenon occurs because the plant allocates more resources to new growth and may reduce its energy directed toward older, less efficient leaves.

The physiological response of darkening leaves comes from an increased production of chlorophyll, which is often a response to nutrient imbalances. The shedding of older leaves is a stress response as the plant attempts to maintain balance and function efficiently, essentially prioritizing the health of its newer growth. Thus, the effects of excessive phosphorus manifest notably through these symptoms, leading to notable changes in the overall appearance and health of the plant.