|I saw a lorapetalum topiary but was told that it would not work well under a porch. It is not a screened porch.
|If it is truly sunny you might try a lantana tree-form topiary. It could be outside much of the year but you would need to protect it when temperatures drop below about 50 degrees in order to maximize the blooming period, then bring it indoors for the winter. Lantana likes it hot and sunny so it handles that baking hot afternoon sun with reflected heat quite well.