Is it safe to grow milkweed over a septic drain field?
Question:
Is it safe to grow milkweed over a septic drain field?
Answer:
As much as we love milkweed (Asclepias syriaca) for its attractiveness to pollinators (not to mention monarch butterflies), I believe I would hold off on growing it over your leach field. As you probably know from your question, leach fields are engineered design structures that can get clogged or damaged by deeply-rooted plants, and milkweed does put down a taproot that can reach several feet deep. An errant one here or there might not make a huge difference, but I would worry that even a small patch might interfere with the septic system’s performance and wind up costing you down the line.
The Clemson Univ Extension has a nice guide to landscaping over leach fields , and you might find this previous Ask an Expert response helpful in coming up with alternatives.
Happy gardening.