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Any favorites in the category of deep purple to black foliage for bedding purposes?
This site features photos of a couple of standbys (I haven't tried the Trifolium).
I have Eranthemum nigrum* growing under lights and it looks like a possibility, depending on vigor outdoors (sluggish growth here has limited the uses of a deep chocolate-purple Pseuderanthemum, and Graptophyllum 'Chocolate') on initial trial was less than energetic).
*is E.nigrum 'Ebony' any different from the species? And why isn't the species listed in the RHS plant bible?