I received a query from a homeowner who wanted a factsheet about planting over a septic drain field. The homeowner wanted some perennials that would thrive on utter neglect — don’t we all?
I searched the internet and found an article in the Tallahassee Democrat newspaper on this very topic, written by Mark Tancig, Water Resource Specialist for Leon County Public Works and Community Development. Knowing how the septic system works will help you understand why the plants surrounding the drainfield could affect the performance of the system.
Key points in the article were listed:
- Use mulch berms, flower beds, site grading, or roof gutters to direct rainwater around your drainfield. This keeps water from saturating the area, allowing the treated wastewater to better soak into the ground. Be careful not to drastically change the flow of rainwater onto your neighbor as this may need a permit.
- Do not irrigate the area surrounding your drainfield.
- Try not to compact the soil with vehicle or heavy foot traffic. Compact soils minimize how much water can be absorbed.
- Support a good stand of herbaceous plants (die back to the ground every year) over the drainfield. Plants with shallow, fibrous root systems are best as they have little potential to clog the piping network. Turfgrasses are best for this. The important things to remember are to choose plants that have shallow roots, do not require irrigation or fertilization, will not require tilling, and that do not form a dense canopy over the soil.
- Do not mulch the soil over the drainfield since this will retain moisture in the soil.
- Do not disturb the soil and wear gloves when doing any yard work around your drainfield. (Source: http://blogs.tallahassee.com/community/2014/05/21/landscaping-around-your-septic-system/)
Needless to say, perennials are not a particularly good choice. Virginia Cooperative Extension states that shallow-rooted herbaceous plants such as flowering perennials and annuals, turfgrass and many ground covers are best. Additionally, considerations of soluble salts from the drainfield and a moist soil in the area, it would be well advised to consider violets, bee balm, daylilies or roses as plants for such a situation. (Source: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-617/426-617_pdf.pdf).