Calibrachoa double-flowering

In Calibrachoa, double-flowering is classified as the presence of more than five petals, which is an important ornamental breeding trait. Standardized quantitative scales for its assessment are absent; therefore, variety trials utilize a descriptor classification that divides plants into double and non-double forms.

The trait is characterized by instability during seed propagation, which necessitates the use of vegetative propagation to maintain flower form. In some cultivars, double-flowering may be expressed incompletely as a partial transformation of stamens into petals or the appearance of 'semi-double' structures, which depends on flower development conditions.

Double-flowering affects the plant's biological interactions, specifically by reducing flower attractiveness to insect pollinators due to the transformation of stamens and decreased pollen availability. However, this morphological trait does not require any changes to standard agronomic protocols for crop cultivation.