Answer: There are literally hundreds of plants to choose from! I'd go for plants with big, bold foliage to create that tropical look. OSU has a publication with lots of lists of lots of plants that not only do well in your area but are categorized for sun, shade and everything in between. Here's the address: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1...
Or, go to the OSU website and look for their publication HLA-6410 Perennial Flowers for Specific Uses in Oklahoma.
Best wishes with your garden!
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