Septic mound plants
Are common milkweed ok on my septic moundy
Cook County Illinois
Thanks for your question to eXtension.
Everything I've read about landscaping on top of septic mounds indicates that the plants need to be able to tolerate DRY conditions. This is kind of opposite of what most people think of when they consider septic systems, but the mound is designed to not hold water.
Milkweed tends to need moister soils than these mound systems will provide. I would recommend that you choose some of the plants listed in this Purdue publication: https://www.extension.purdue.edu/extmedia/HENV/HENV-15-W.pdf .
Please let me know if you have any other questions.