I have 'Black Barlow' and Geranium phaeum 'Sambobor' (the flowers are dark purple and there is a dark blotch on the leaves). I will be listing those in the Piggy Swap.
I have had a "Dark Side Garden" for years now, and I am still increasing my stock.
I am not sure I have the seeds from my dark dahlia. I will have to check the bag.
The Black Mondo Grass would be something to aquire, as mine grows quite slowly...not yet enough to share.
to our happy little world of plants...