The leaflets of the elder (Sambucus sitchensis) leaf on the left are distorted because of fluoride accumulation in the margins and tips during growth. Note that the lowermost pair of leaflets is normal but the younger ones are distorted. The tips are indented, heart shaped and buckled (one, on the right was eaten by an insect). The leaf on the right is from the same branch and its leaflets show chlorosis (=yellowing) of the margins and interveinal regions but little or no distortion. This photograph illustrates the importance of the timing of a fumigation in relation to stage of growth and the variation within a single plant if leaves develop and grow at different times.