I wouldn't use black for a covering, I would use a aquarium type background.
When my packman was small he always tried to go to the side that had the heat pad on the
enclosure that was black even if it was off. and the other sides had aquarium background.

As far as the plant I have never had live plant with him since he always burrowed and could
dig up the plant.
I don't think the frog is in any danger from the plant but the plant could be the victim here.