Is it safe to grow comfrey over a septic drain field?

Asked June 7, 2019, 6:49 PM EDT

My septic system's drain field currently just has a bunch of bracken growing on it. I'm interested in growing comfrey in order to compost it and improve my garden. I'm planning to plant the Bocking 4 variety, because as a hybrid it's supposed to be unable to spread through seeds. I'm reading mixed reviews online about whether it's safe to plant comfrey over a septic drain field: Some sources say that nothing with deep roots should be planted near the field, while others say that bioaccumulators like comfrey are an excellent choice. What's your verdict? Do you expect comfrey to reach below the drain field and lift nutrients out, or is it more likely to stick its roots into the drain pipes and make an expensive mess? Thanks for any advice!

Benton County Oregon

1 Response

We do not recommend growing any shrub over a drainfield. The root systems can compromise the area, depending on how deep it was installed. New drainfields are expensive and it may not be worth the hassle. We recommend other shallow rooted grasses and flowers. Something like a vetch or other legume may be good if you want to use to add to compost.