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PHOTO of a northern Minnesota field where we have ample room to keep septic components well away from the trees - but notice those tire tracks?Planting Trees or Shrubs Near Septic or Sewer Lines

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Guide to Planting Trees or Shrubs Over or Near Septic System or Sewer Lines:

This article describes the types of trees, shrubs, or similar 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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Planting Guidelines for Septic Drainfields, Mounds, Raised Beds, Septic Tanks and other Septic Components

Photograph of a tree which can be placed over septic system components

Planting fruit trees, or vegetables (or anything else edible) over the septic drainfield might produce food that is unsafe to eat:
see SEWAGE CONTAMINANTS in FRUIT / VEGETABLES for details.

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

This is the only sort of tree that we suggest can be placed over septic system components with little risk of damage.

This is actually a metal sculpture. Even the placement of this "tree" could have damaged a septic field if during its installation heavy equipment was used to deliver the tree to this spot. Real trees will damage septic components by root movement or clogging.

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.

Watch out: 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: keep shrubs with a “known” root travel distance 25% farther than that distance from the edge of a drainfield.

In this photo the light and excavated area is where the new home owner saw and dug into a smelly wet spot that appeared in the yard the morning after moving into their new home - a house built 30 years before and one which employed a home made septic tank.

Photo of a failed septic field with nearby trees.

While there were tree roots in the drainfield pipes of the system, the septic tank itself, which was too small, never pumped, and fully blocked, was the "root" cause of system failure in this case. (Pardon the pun).

How much distance is needed between trees and septic drainfields?

White pines 30 years old (C) D Friedman

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:

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?

Roots entering a clay sewer line in Seattle WA (C) D Friedman L Shields More root invasion in the sewer line found with sewer video camera (C) Daniel Friedman Lee Shields

Above: the video camera line inspection shows a modest dislocation in a sewer line pipe joint through which roots are growing. Even a small root intrusion or pipe joint dislocation can accumulate or block the flow of solid waste leading to slow gurgling drains and ultimately to a complete drain blockage. Our photos above show root invasion at 27 feet and at 83 feet in this buried sewer line in Seattle, WA.
See SEWER / SEPTIC PIPE CAMERAS

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:

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.

Shrubs or Trees Recommended as Suitable for Planting Over / Near Evaporation-Transpiration Septic Systems

The following table of native (to New Zealand) or introduced species of shrubs and trees lists species that are considered suitable for planting over an evapo-transpiration system and should be acceptable over a mound system or conventional drainfield as well. Note that other native species local to your area might also be suitable. [3] Separately at Grasses or Flowers we provide a similar table of suitable grasses.

Table of Shrubs or Trees Suitable for Planting Over / Near Evaporation-Transpiration Septic Systems [3]

Common Name Botanical Name Comments
Aralia    
Begonias    
Cabbage tree Cordyline Australias fast growing
Canna lilies    
Coprosma Coprosma propinqua  
Flax Phormium Tenax fast growing
Fuscia    
Hebe Hebe  
Heketara Olearia Rani  
Hetz Wintegreen Thuja occidentalis 18-24" deep, 5 ft. spread roots
Kohuhu Pittosporum Tenufolium fast growing
Lacebark Hoheria Populnea fast growing
Pokaka Elaeocarpus Hookerianus slow growing
Rangiora Brachyglottis Repanda fast growing
Ribbonwood Plagianthus Regius fast growing
Manuka Leptospermum Scoparium  
PhilodendronsPoataniweta Carpodetus Serratus  
Taro    
Weeping mapou Myrsine Divaricata  

Notes:

Original source: "Looking after your household sewerage system," New Plymouth District Council, Taranaki NZ, [3]

Also see GRASSES or FLOWERS ok to plant over septic systems and drainfields or soakaway beds.

Table of Recommended septic distances for Apple trees, Hazelnuts, Hetz Wintergreen, Lindens, Tamarinds, Norway Pines & Red Spruce Trees, Poinciana, Redbud Trees, Witch Hazel Trees

Table of Recommended Shrub or Tree Distances from Evaporation-Transpiration Septic Systems [3]

Common Name Botanical Name Recommended Minimum Horizontal Distance to Septic Soakbed or Drainfield
Blue Spruce trees    
Dwarf Alberta Spruce trees Picea glauca 'Conica' 30 feet
Hazelnut trees Corylus 50 feet
Honey-Crisp apple tree Malus domestica 1.5 x anticipated tree height or about 30 feet for a typical fruit tree, plus safe distance from wind-borne aerobic septic effluent sprays
Linden trees Tilia 100 feet
Neem trees   50 feet or more; deep tap root.
Poinciana trees Delonix regia 100 feet or more; roots spread horizontally 4-10 feet / year and grow to 10+ feet in depth
Redbud trees Cercis canadensis 25-30 feet
Red Pine / Norway pines Pinus resinosa 60 feet
Red Spruce trees Picea rubens 100 feet
Tamarind trees Lysiloma latisiliquum 100 feet
Witch Hazel Hamamelis virginiana 25-30 feet; some are surface rooting but can spread 20+ feet. Hamamelidaceae.
     

Notes:

Also see GRASSES or FLOWERS ok to plant over septic systems and drainfields or soakaway beds.

How far from a drain-field should I plant a Honey-Crisp apple tree?

This discussion has moved to TREE or SHRUB DISTANCE FROM SEPTIC FAQs

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Continue reading at ROOT KILLERS in SEWER LINES or SEPTIC PIPES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see TREE or SHRUB DISTANCE FROM SEPTIC FAQs - questions & answers posted originally at this article

Or see SEPTIC DRAINFIELD FAILURE CAUSES

Or see these

Articles on Plants & Grasses On or Near Septic Systems

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TREES or SHRUBS OVER THE SEPTIC FIELD or TANK at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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