Planting native hedge near sewer lines?

Asked January 6, 2019, 12:34 PM EST

I am planning to plant a native hedge along my property line, next to a newly installed fence. Our sewer lines are five feet from the property line, which is right about where I want to plant. I'm not certain how deep they are. Are there any plants to especially avoid in this situation? I'd been thinking of using garrya elliptica, tall Oregon grape, Western service berry (pruned as a tree), ceanothus, redflowering currant, nootka rose, snowberry, and a mix of perennials and grasses. Thanks for any advice!

Clackamas County Oregon trees and shrubs wildflowers and native plants

1 Response

Thank you for your question. Although there is not a lot of literature about planting near sewer lines, there are several helpful resources for planting near a septic field, a similar system. As an Idaho Extension article (http://www.cals.uidaho.edu/edComm/pdf/CIS/CIS0991.pdf) indicated:

"Trees or shrubs planted too close to septic systems and sewer lines can create major damage. Roots can penetrate cracked tile or loose pipe junctions, and are the item most frequently found in drain and sewer pipes. In addition to clogging sewer lines and septic systems, the expanding tree roots can lift or crush sewer lines or cables, creating additional problems related to service loss, environmental hazards, and costly repairs. The safest practice is to plant trees and shrubs as far away from underground utilities as possible; however, if you must plant in these areas, avoid species such as willows, poplars, and cottonwoods with dense, fibrous roots. "

I am not certain how old your sewer pipes are, but, with age, they also become increasingly susceptible to breakage due to equipment being driven over them. The following WSU Extension article discusses those concerns, and has suggestions for plants whose roots will not penetrate and break the pipes, and include suggestions for native plants, which your list emphasizes: https://s3.wp.wsu.edu/uploads/sites/2079/2014/02/landscaping-septic.pdf

Frankly, it is difficult to find a compendium showing how deep a root system of a plant is (although we know rhododendrons and azaleas are quite shallow.)
And, as for hedges, the following article addressing septic field recommends no trees or shrubs: https://www.canr.msu.edu/news/could-you-please-tell-me-what-native-plants-i-can-plant-on-the-drain-f...

I hope this information is helpful to you. Good luck!