My mom placed a birdbath in the middle of her septic mound, then planted cannas and glaadiolas all around. Of course,they need to be dug up at summer's end and stored. It's lots of work,but it sure is pretty!

My civil engineer buddy says no plants with deep roots on the septic field or you'll clog up the works. She says grass is best and moss is not good.

Don't know how it will work up there, but here in Central Florida I have planted moss rose on my septic. (like 87 cents each at WalMart) Loves the sun, no deep roots. Once established after about a week, I only water about once a week. Well, we've had NO rain this year, so have to water everything. Over the outlets I have pots that I put geraniums in. I just couldn't push the mower up and over the darn thing anymore.