| The Master Gardeners occasionally get questions about planting over a septic drainage field. This came up as a “chat” query during Margaret Payne’s recent Zoom presentation to the Lopez and Orcas garden clubs.
If a home is in a wooded area, the only sunny spot might be the leach field. A leach field could be in an area in front of a home that the owner wants to make attractive. There is a lot of new construction in San Juan County right now including installation of septic systems.
This is a complicated issue with a few pros and several cons. The short answer is that some plantings are OK. The reference from Clemson University Extension has a good discussion of the issues. It emphasizes examining the site map of the drainage field. The reference from WSU Extension has recommendations for our area regarding what can be planted and what should definitely not be planted.
According to the reference from Clemson University Extension there are three basic principles regarding planting over leach field.
- Don’t do anything that might penetrate the fabric covering the drainage pipes in the leach field. No digging more than a few inches and no planting of anything that will grow deep roots.
- Don’t do anything that could impede the diffusion of air into the soil. The air is needed to help decompose waste water. Do not put in covered walkways or raised beds.
- Don’t grow produce for human consumption over a leach field.
For more information, please see these reference sources:
https://hgic.clemson.edu/factsheet/landscaping-over-septic-drain-fields/
https://s3.wp.wsu.edu/uploads/sites/2074/2014/01/Septic-Landscaping-and-Planting-Conventional.pdf
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