Between Sri-Lankan holidays and freak illnesses, I have been in the process of filling out our new simple pvc planters which we have added all around the perimeter of the rooftop garden. We chose an 8 inch pipe and end-caps, and added 4 inch diameter openings along the top. The openings are about 4 inches apart to give plants a healthy stretch for roots. In the bottom left corner of the image you can also see tiny drainage holes on the bottom half of the end-cap. There are 5 to 8 additional drainage holes along the bottom of the pipe which allow excess water flow to planters below.
To fill the pipes I began layering stones over the drain holes and rough, gravely soil from the driveway. I topped this with layers of newspaper and cardboard to encourage beneficial fungal growth and topped with a homemade potting mix of sand and compost. As the soil settles I add more shredded paper and compost. To prevent deterioration of the piping from our strong sun, I painted the pipes to match our arbor and posts. A simple coconut coir rope trellis will support our winged beans making their way up to the arbor. The only tools required were a drill, screw-driver, and hacksaw (which a local machine shop used to cut the holes for us). I opted not to glue the caps on (they fit very snuggly) so that I can empty the pipes if ever needed.
So far, we are seeing success in the pipes among our beans and herbs. Below you can see our young winged beans.