Abstract

Many eucalypts are heteroblastic, exhibiting a distinct change in leaf morphology through their ontogeny. The physiological and chronological age at which the tree switches from the production of juvenile foliage to adult foliage (vegetative phase change) can be under strong genetic control and influenced to some extent by environment. We studied the effect of nitrogen (N) and phosphorus (P) fertiliser on the growth and vegetative phase change in Eucalyptus nitens. Whilst neither fertiliser treatment affected tree height at 3.5 years of age, P fertiliser significantly reduced the length of the juvenile vegetative phase. In contrast, N, but not P, has been shown to promote flowering. These findings support the argument that vegetative and reproductive maturity are genetically and physiologically uncoupled in Eucalyptus.