Planting Trees or Shrubs Near Septic or Sewer Lines – InspectAPedia

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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.

We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Watch out: While not all sewage or septic system effluents will always make nearby fruits or vegetables unsafe, in at least some conditions planting fruit trees, or vegetables (or anything else edible) over the septic drainfield might produce food that is unsafe to either because watering or rain splash-up sends sewage-contaminated water droplets onto the surface of the edible fruits or vegetables OR because in some cases pathogens may enter the plant system by means of its roots.

Wee SEWAGE CONTAMINANTS in FRUIT / VEGETABLES for details.

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 itd 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.

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).

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

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.

Trees considered to have deep and/or aggressive roots that are likely to damage a drainfield include those listed below.

Japanese Angelica Tree, considered invasive in the U.S.

Warning: dense root system may kill nearby plants and block soil oxygenation.

See also Aralia spinosa in table below.

Sources

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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 nearerto 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 likelyto 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 itd be ok to plant it exactly that distance from the nearest drainfield trench.

But Id 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: Id keep shrubs with a known root travel distance at least 25% farther than that "known root travel distance" from the edge of a drainfield.

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

In the photo at the top of this page, our field in northern Minnesota provided ample room to place septic system components more than100 feet from the nearest tree. But what about those tire track that show up in light snow? Driving over the drainfield can alsodamage it.

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.

Shallow root system, Native in South-Eastern U.S. Common names: devil's walkingstick, prickly ash, Hercules club, angelica tree, prickly elder, pick tree, toothache tree, shotbush

Watch out: see Aralia elata in table above.

Root depth 8 to 24" depending on species; non-aggressive, shallow spreading roots.

Might be ok over drainfield trenches more than 24" deep but safer to keep at least 25 ft. away or distance = canopy diameter + 10 ft. .

Original sources:

Watch out: even when trees are listed as OK to plant near a drainfield that NEVER means planting right atop the drainfield, and some of these trees must be kept considerable distance away.

Keep trees at least twice as far from the drainfield as canopy height or twice as far as the tree's expected root spread.

Blue sprue roots are shallow, just 2-3" deep,and slow growing, but the roots may extend 2-3 times the diameter of the drip line or the largest diameter of the tree canopy.

See Fechner, Gilbert H., BLUE SPRUCE Picea Pungens [PDF] USDA

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

Day provides suggestions for using a root barrier - excerpting:

Another effective,although expensive, technique that may be worth trying isinstalling a root barrier between your drainage field and treeplantings. Geotextiles, impregnated with a long-lasting herbicide that moves only a short distance in the soil, have beenused successfully to restrict root growth in street tree plantings.

To effectively stop tree roots, the barrier should extend from the soil surface to a depth of at least 2 feet.

Some roots may still grow under the barrier, but intrusion into the drain field should be greatly reduced. Install the barrier fabric at least 3 feet from the drain field so as not to disrupt the system. Allow at least 5 feet (the more the better) between the tree and the root barrier - more if it will be a very large tree.

Finally, never encircle the tree with the barrier material; this could effectively containerize your tree and prevent it from thriving. Instead, run the material the entire length of the drain field to prevent roots from getting into the field by going around the barrier.

Excerpt: This small suckering hardy tree or large shrub is nativethroughout North Dakota. Purple-leaved selections are popular landscape plants.

Fruits commonly used for jellies and jams. The largest tree form in North Dakota is 41 feet tall with a canopy spread of 28 feet.

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

@Inspectapedia Com Moderator, Thank you for your response and recommendations.

@Kendell S,

From what I've read Elaeagnus has both a deep tap root and a spreading more-shallow root system. You should not plant this over your drainfield nor close to it. Normally we keep such plants well away from the septic drainfield - a distance greater than the expected canopy diameter which often predicts the minimum horizontal roof spread.

The plant is said to grow to > 9m in height and at least 4 ft or 1.3m wide and are usually kept 3m or more apart even from one another.

That planting separation recommendation you'll find at various plant sites for Elaeagnus would say your plants need to be 9 ft. apart and I'd figure for safe avoidance root invasion of your septic field you'd want plants no closer than 10-12 ft from the edge of the drainfield.

My reasoning is the experience that the high concentration of nutrients in septic effluent act as a sort of magnet that can attract the roots plants from greater than normal plant root horizontal or vertical distance.

How safe are Elaeagnus for a privacy shield say 6 feet apart over or near my septic drain field which distributes pumped effluent?

@Jill S,

Sorry, you're both right to ask for clarification of my earlier reply.

You can remove the trees if you like - saw down, cut up, carry away.

Leaving tree roots (and stumps) won't in and of itself cause trouble.

If roots are already in the drainfield piping then they're already causing trouble, dead or alive - by clogging the system and reducing its capacity - that's why I suggested a sewer line cam inspection.

Left in place tree roots and tree stumps of many species will ultimately begin to grow anew - so you haven't necessarily "killed" the trees and you might still in the future see a root invasion problem.

Watch out: driving heavy equipment over the fields such as a stump grinder or a truck to pick up tree parts can compress soil or collapse a drainfield line - damaging the system

My husband and I interpreted your response differently. If we would like to remove a few pear trees, should we be concerned that it might negatively impact the septic leach field?

@Jill S,

Ornamental pears like the Bradford tend to have shallow roots: perhaps you've been lucky and they haven't invaded your septic drainfield.

Why not have a sewer line camera inspection of the leach lines: if you see they are root free you might stop there.

We live in North Carolina and our septic system is almost 20 years old. There are ornamental pear trees and holly trees planted over the leach field. The pear trees are now three stories tall.

We have not had any problems with the septic system and are not sure if its better to just leave the trees or cut them down? In particular, if we remove the trees and the roots have invaded the septic field could this cause problems when the roots start to decompose? Thanks, Jill

@BRIAN RASMUSSEN,

The root system for Yucca plants are invasive, aggressively-seeking water (and storing it too), combined of a shallow root system seeking water and a deeper tap-root.

I've found that "normally-shallow" root systems will be attracted to a drain line if there are openings (hub type older drainfield pipes) and will absolutey be attracted to the drainfield trenches of septic systems.

So you'd want to keep such plants 2-4 x the plant's canopy size diameter away from the drainfield. 20-30 feet or more may be safe.

See details in this

YUCCA PLANT INFORMATION GUIDE - USDA [PDF] USDA, retrieved k2022/01/24 original source: https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/nmpmcrb12162.pdf

Available here at

https://inspectapedia.com/septic/Yucca-Plant-Information-USDA.pdf

Are Adams Needle yucca variety damaging to drain pipes and septic systems? Thanks, Brian

@Field Inspector K-Sneak,

You did a GREAT JOB KS - by working by hand and carrying off the cut-up logs from the septic mound.

That means you didn't drive heavy equipment over the mound system.

Now as long as there was no evidence that the tree-fall broke a pipe - which from your photos and our onsite inspection seem to be the case, and as long as the remaining end of that big tree is not on any part of the constructed septic mound, you can leave the rest of it alone if you like.

That sawdust won't hurt a thing - it's only of cosmetic import - because of its limited thickness and because it's spaced out. (You would not want to pile many inches of sawdust or any other compost atop the mound) as in too much thickness you might interfere with transpiration or with the availability of oxygen to the aerobic bacteria in the soil top layers.

@inspectapedia.com.moderator,

Update on the tree that fell across our septic mound system:

As you can see in my photo, I got that nasty old chain saw working an cut the tree into short segments that I could carry off of our septic moun. I stopped cutting back the fallen-tree once I had removed everything back to the bottom edge of the mound.

1. Is it OK for me to leave that sawdust on the septic mound or might it cause a mold problem?

2. Is it OK for me to leave the rest of the tree in place?

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Planting Trees or Shrubs Near Septic or Sewer Lines - InspectAPedia