Answer: Most evergreens require a well drained location, but you could try Ilex glabra the inkberry holly. Some decorative deciduous plants to try would be Aronia arbutifolia, Itea virginica, and the shrub or "twig" dogwoods such as Cornus sericea.
Ants can be difficult to treat unless you can locate the nest, but based on your description nest may well be in the box. In general, outdoor ants do not need to be controlled unless they are entering the house or are causing root disturbance -- which they would in a planter situation. The following article suggests control methods for ants outside.
I hope this helps!
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