Cultivar groups are based on several physical traits, i.e. crenate or dentated phylloclades & symmetrical or asymmetrical flowers.
ORSS – cultivars with dentated stems and broad large sized zygomorphic flowers with a spiked corona ring, showing no reflex.
If you are looking for large sized flowers in different colors and even some double ones, this is the type to go for.
RUSS – cultivars with crenate stems and pending symmetrical flowers.
Smooth stems and nice pending flowers like two staged bells van be found here. For people who like to see balance in their plants.
ENIG – cultivars with thick small stems and buds opening from the start.
Looking for odd things. Fat stems and surprising and intriguing buds that at the end develop into sometimes strange formed flowers.
EXOT – cultivars with ridged (edged) stems.
Strange formed stems come in different sizes. Decorative even when not flowering.
TRUN – cultivars with dentated or crenated stems and small to medium sized zygomorphic flowers. A large group of cultivars with flowers in many different forms and in many colors. They are the sturdiest growers. All plants available in shops and garden centers will fall into this category.