What are the best flowers for a leach field?
Question:
The septic tank and leach field were just installed at my new home (there is nothing growing on it at all, just dirt). The slope off the back side of the leach field is steeper than what I’m comfortable mowing. I read an article here titled “establishment of vegetable gardens on septic system disposal fields” by Katherine Garland. In the article she says, “The most suitable plants to grow on top of septic system disposal fields and fill extensions is grass. It is also permissible to grow flowers, but only if the soil is not rototilled and minimal watering is done.” My question is, what are the best species of flowers that we can we grow safely over the leach field and side slopes? It is in full sun. We’d like something that we can plant and forget it.
Answer:
For a leach field, you are looking for something that won’t have a terribly deep root structure (to avoid interfering with the components of the structure) and that are reasonably tolerant of dry conditions (since soil over leach fields tends to be poor quality). For flowers, I would consider creeping phlox (Phlox stolonifera), dianthus (Dianthus spp), creeping thyme (Thymus serpyllum), and violets (Viola spp). All meet those parameters and are pretty low maintenance.
My colleague (and author of the article) Kate Garland suggests hay-scented fern (Dennstaedtia punctilobula) for the sloped portion, though she also advises that many desirable plants may spring up there as time goes along and suggests this video from Bowdoin College to put you in that mindset.