As a point of definition, you wouldn't have a bog garden with that set up. From what I've heard concrete isn't the best substance for true bogs (which also would not require soil or compost, just peat and sand). You could make it a true bog if you lined it first.

That said, you could do a nice wetland garden. You might plants that like somewhat shady and "mucky" conditions like skunk cabbage, or false helebore. I'd also recommend using the blue cardinal flower instead of the red since the Red prefers more sun. Also try marsh marigold which can take shade.

Good luck!

Lonnie

Thanks for your response. I guess I am a little confused...while it is concrete, it has been painted with a waterproof product of some kind: It is completely watertight. And I certainly don't mind usuing a combination of peat and sand.

Simcan,

Bogs are very specific ecosystems which are sunny and acidic, with very little disolved minerals. In fact, even most people's tap water is too dirty to use for a bog garden. Lining it wouldn't be for the sake of making it water tight, but rather to keep the concrete from leaching minerals.

That said, given that you have a shady location anyway, I wouldn't go for a true bog garden anyway. Instead you might go with something approaching your original plan of a richer soil mix and swamp/wetland plants.

Also, I'd add wild calla to that mix of plants I suggested as well.

Sounds good, thanks.