Canna indica and its subspecies generally have smaller flowers with narrower parts.
Canna indica has staminodes that are under 15 mm wide.
The cultivars generally have larger and colourful flowers.
Their staminodes are 5 to 6 cm wide.
Canna x generalis is sometimes used to describe any cultivar or hybrid with large flowers.
There are hundreds of named cultivars.
Many are similar in appearance.
The same cultivar can also be known by many synonyms.
It needs a Canna specialist to identify them all.