Ivy is one of a small number of plants that exhibit different juvenile and adult forms.
Young growth consists of creeping or climbing stems bearing numerous fine, aerial roots and (usually) lobed leaves - this is what most people think of as ‘typical’ ivy. It’s the vigorous growth stage, when the plant spreads rapidly.
When the plant reaches maturity it produces rootless, self-supporting stems with unlobed leaves. The adult growth bears the flowers and fruits but these are only produced in full sun. Very old ivies may look more like shrubs than climbers.
Ivy flowers very late in the year, from September to December. The flowers are pollinated by wasps and moths, providing a useful food source for these insects.