Answer: Have you considered attaching decorative chains from the eaves of the porch? The chains will direct the water down to the ground (and into the underground pipe) and still look attractive. (Just a thought). You can safely plant on either side of the pipe. The roots of your shrubs will simply grow around the pipe. I don't think the feeder roots will clog the pipe, especially if they have adequate water and do not need to grow into the pipe to seek water. But, for added security, you can lay weed barrier over the pipe. This polyprophylene material has tiny holes in it - enough to allow water to seep in but not roots.
Best wishes with your new project!
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