We originally had old cedar columns on our porch. As part of our porch renovation project, we decided to add an apron to frame the porch ceiling and then we wrapped the cedar columns with Hardie boards. Below is a glimpse of one of the columns. 
Here is a before picture (also before the outdoor fireplace and old barn wood ceiling. Notice in the picture below the old columns on the far left and that there is no apron around the edge of the ceiling.