SIMPLE FLOWER: Flower with one or two rows of petals and a well visible stamens center.
SEMI-DOUBLE FLOWER: Flower bearing many rows of petals but still with a well defined stamens center. Some stamens could be transformed in petaloïds ( kind of small petals).
DOUBLE FLOWER: Flower completely covered with petals. In general, the center of stamens has disappeared being transformed in petals. Sometimes, the double flowers may still have some useable carpels hidden by the numerous petals.
BOMB TYPE FLOWER: Completely double flower where the center petals form a ball on top of the flower which is very distinctive from the guard petals. Stamens and carpels are absent.
JAPANESE FLOWER: Simple flower whose stamens has been transformed in petaloÏds (like small petals) creating a more imposing center.