Why Plant Leaves Turn Yellow - Yellowing foliage is direct evidence that something has gone awry in the plants' environment or care.Why Plant Leaves Turn Yellow - Yellowing foliage is direct evidence that something has gone awry in the plants' environment or care.Why Plant Leaves Turn Yellow - Yellowing foliage is direct evidence that something has gone awry in the plants' environment or care.Why Plant Leaves Turn Yellow - Yellowing foliage is direct evidence that something has gone awry in the plants' environment or care.