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• Trees or shrubs planting near septic systems
• Advice for planting over or near septic systems

Planting Guidelines for Septic Drainfields, Mounds, Raised Beds, Septic Tanks and other Septic Components

This chapter discusses the types of plants that should or should not be planted over or near septic fields or other septic system components. Planting trees, shrubs, and even some ground covers over septic system components are causes of septic system failure in the drain field, leach field, seepage bed, or similar components.

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Guide to Planting Trees or Shrubs Near or Over Septic Absorption Systems

How much distance is needed between trees and septic drainfields?

Whether you are planting trees or planning a new septic drainfield, keep the drainfield or septic leach field away from trees or shrubs which are likely to put down deep or aggressive roots. The roots will quickly invade and clog the buried effluent lines and may also cause them to move, break, or become disconnected.

The actual tree to septic distance needed depends on the tree variety and its normal root growth range. Keep at least as much distance between the tree and the nearest drainfield component as the anticipated height of the tree at its maturity. So if the tree will be 30' tall at maturity keep it at least 30' from the drainfield. Some trees should be kept at much greater distances, up to 100' from septic fields, as we discuss just below.

What kinds of trees should be kept farthest away from septic systems?

Trees considered to have deep and/or aggressive roots that are likely to damage a drainfield include:

• Bamboo, Beech trees Fagus sp. and Birch trees Betula sp.
• Cypress trees
• Elm trees Ulmus sp. and Eucalyptus
• Pepper trees
• Pine trees, such as Monterey pine
• Poplar trees Populus sp.
• Maple trees, particularly red and silver maples Acer rubrum and Acer saccharinium
• Walnut trees
• Willow trees Salix sp are popularly known for "liking water" and will certainly send out long root systems.

Kahn, Allen, Jones (book cited at Septic Systems Home-References) point out that certain of these trees such as bamboo, weeping willows, eucalyptus, cypress, Monterey pine, pepper, and walnut have particularly aggressive and deep roots. Keep such trees at least 100 feet from the nearest septic field component.

Can I Plant Non-aggressive Rooting Trees near Septic Drainfields?

Some trees have less aggressive roots and may do less rapid or less extensive damage if they are a bit nearer to septic fields. These include:

• Ornamental trees such as Cherry, Crabapple trees, and Dogwood trees.
• Other trees with less aggressive root systems such as Oak trees (red oak, scarlet oak, and white oak)
• Some Pine trees (but not the Monterey pine) and Sourwoods.

OPINION-DF: Some authors accept the near-septic use of these less aggressive trees with the advice that "... their damage is likely to be less severe". This seems silly to me. Any root clogging of septic systems is likely to be costly and inconvenient.

If you have a shrub for which you have reliable knowledge about the maximum extent its roots will normally reach, you might think it’d be ok to plant it exactly that distance from the nearest drainfield trench.

But I’d be careful: the extra levels of nutrients delivered to the soils by the drainfield may attract roots from nearby trees or shrubs and cause them to travel farther than usual.

OPINION-DF: I’d keep shrubs with a “known” root travel distance at least 25% farther than that "known root travel distance" from the edge of a drainfield.

Guide to Planting Trees near Septic Mound Systems

Some experts (Kahn, Allen, Jones) also point out that if you're planting on the edges and lower toe of a septic mound, those plants need to be able to tolerate the higher moisture levels found in those parts of the mound system.

In the photo at the top of this page, our field in northern Minnesota provided ample room to place septic system components more than 100 feet from the nearest tree. But what about those tire track that show up in light snow? Driving over the drainfield can also damage it.

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• "Planting on Your Septic Drain Field", Susan D. Day, Extension Associate; Ellen Silva, former Extension Technician; Horticulture, Virginia Tech. publication Number 426-617, Posted December 2000, published by the Virginia Cooperative Extension, was consulted for some technical details in this article.

More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.

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