Sweet William has dark cultivars.
It is biennial, but might reseed.
This year I am hoping to grow the "Blackberry" cultivar of petunia.
There is a hollyhock with "black" flowers.
Nemophilia has a black form. (annual).
There is a "Black Velvet" Nasturtium.
And also a "Black Beauty" Dahlia.
All of these are more like annuals.
