Regarding _D.capensis_ flowers...
This species (at least most forms in cultivation) are very floriferous.
If you grow them in warm conditions year round they will flower, set seed,
and flower year round. If given a seasonal variation they will only not
flower during the winter (sorry for the negative logical syntax of that
sentence!). Seed is produced copiously via natural selfing so you don't
have to get involved. You should expect a long succession of inflorescences.
Keep flowering specimens of this plant far from your seed pots of other
species or else seeds will infect your other seedpots.
Cheers:
B