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? Guide to Planting Trees or Shrubs Over or Near Septic System Components
     


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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 componentsPlanting 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.

Photo of a failed septic field with nearby trees.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.

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 FriedmanWhether 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. The pines in our photo (above-left) are white pines approximately 30 years old.
  • 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.

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  
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.

What are the Recommended septic distances for Lindens, Tamarinds, Norway Pines & Red Spruce Trees?

Tree Distances from Septic Components for Linden Trees: 100 ft.

Reader Question: 6/23/14 Cynthia said:

Are linden trees safe to plant near a septic system?

Reply:

Cynthia

I would keep a linden tree 100 feet from septic components. Linden trees grow to 89-90 feet in height, a size reflected as well in their very extensive root system, making the linden tree likely to invade septic systems if too close.

Tree distances to septic drainfield for red pine / Norway pines: 60 feet

Reader question: Have you any information on Norway PInes and Red Spruce as i have these planted in my yard and am concerned about there potential damaging effects on my septic system.. thanks. . they r only 4 feet so far so i can transplant them if need be - Will Treeman (4/11)

Reply: 40-60 feet for a 20-40-year early tree-life range, longer for longer tree life expectancy

According to Pennsylvania State University "The red pine is a native North American tree species sometimes erroneously called the "Norway pine". ... Red pines grow very rapidly for their first 60 or 70 years of life. They can live for up to 350 years and reach heights of 120 feet and diameters of up to three feet. " [1]

Using a 60-year planning time frame, and our rule of thumb for distances of normall-aggressive-root-system trees from septic drainfields, assuming a 60-foot tree height, I'd keep my red pines (or "Norway pines") sixty feet away from the drainfield. 100 feet would be safer as pines can have aggressive root systems.

Tree Distances from Septic Drainfield for Dwarf Alberta Spruce Trees: 30 feet

10/10/2014 Daryell said:

Dwarf Alberta Spruce Tree distance between leech field?

Reply: Daryell

The roots of a Dwarf Alberta Spruce tree are typically 10-15 feet in all directions from the trunk. 30 feet or more should be a safe distance from the drainfield or soakbed or leach field.

Tree distances from septic drainfield for Red Spruce: 100 ft.

According to the University of Maine's Maine Tree Club, "Red spruce can attain a height of 60-80 feet and a diameter of 1-2 feet. It will occasionally exceed these measurements." Synonyms for red spruce include Yellow Spruce, West Virginia Spruce, Eastern Spruce, He-Balsam" Picea rubens, [2]

So the same rule of thumb as for red pines applies: if you don't want the trees to ever threaten the septic drainfield for the next 30-60 years, promising the trees a long and happy life, keep them 100 feet from septic drainfields.

Note: guessing at the tree root area and health for red spruce is complicated by soil chemistry and nutrients and so guessing root area size based on canopy size is less reliable for this species. [3]

Tree Distances from Septic for Tamarind Trees: 100 ft.

6/22/14 Anonymous said:

How far from drain field should a Lysiloma latisiliquum or false tamarind be planted?

Reply:

We found several authors who described rather aggressive root growth and a need for periodic root pruning in ornamental use of the False Tamarind plant. I'd follow the more aggressive distances given in our tables above, keeping ab out 100 ft. to be safe.

Tamarind trees have both a deep tap root and very aggressive root structures that would be likely to invade and clog a septic drainfield.

 

Continue reading at USING ROOT KILLERS in SEPTIC FIELDS or select a topic from the More Reading links shown below.

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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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