Q&A about planting grasses, trees, shrubs on or near septic tanks and septic fields:

Questions and answers about safe distance from the septic fields for various plants.

This article series is a guide for homeowners who are planting trees, shrubs, gardens, ground cover, or other plants near a septic system and who need to know that can be planted near or over septic system components like the septic tank, distribution box, and drain field or soil absorption system.

Plant Distance & Plant Type FAQs for Septic Fields

These questions and answers about planting near septic systems were posted originally

at PLANTS & TREES OVER SEPTIC SYSTEMS - be sure to review that article.

On 2018-09-08 by Janet - Hydrangeas ok near the septic field?

I am wondering if I can plant hydrangeas near my septic drain field ...what would be a safe distance from the drip lines?

On 2018-09-08 by (mod) - safe planting distance for hydrangeas near septic system

Thanks for asking, Janet.

Hydrangeas use a rhizome type root that stays principally in the top 6-inches of soil - so it would not be expected to invade the drainfield absorption trenches or drip lines.

It would be smart to keep the plants away from the drainfield by a distance no less than the full width of the plant's visible foliage when it will be mature.

As a mature plant is about 6 feet (2 meters) in diameter, a ten foot distance ought to be safe.

How to kill weeds growing on the drain field.

Hi,
I did not see anywhere in article related to spetic tanks on how to kill weeds growing on the drain field. How does one go about doing it?
I

was planning to put plastic sheeting over the "baby" weed next year, but this article https://s3.wp.wsu.edu/uploads/sites/2144/2015/03/Spotlight-on-Planting-over-Septic-Drainfields.pdf says not to put any platic sheeting.

What do i do? The whole of the field is full of ferns, blackberry brambles etc. Overwhelmed on tyring to figure out how to kill them off.

Thank You,
AJ On 2018-07-02 by AJ

As you can see it full of all kind of stuff.i was going pull all them out - it's a major eye sore.

my father in law is insisting on pulling all the weeds, putting down loam over it and growing native grass - is that a good idea?

Here is the sketch of the system.

do you if i can aerate over the septic tank. i have grass growing there but it is thining and i wanted to aerate and add more grass.
Thanks!

On 2018-07-02 by (mod) - importance of avoiding covering a drainfield with anything that blocks its exposure to the air.

AJ

Thank you for the question and for this chance to clarify the importance of avoiding covering a drainfield with anything that blocks its exposure to the air.

You didn't read about plastic in the article on THIS PAGE because this is an article about plants. As editor I worry that if I try to put every single mistake about septic drainfield on a single page the article is so long that it's not readable. However this article *series* does include the plastic over drainfield warning.

Throughout this article series we warn against both invasive roots that can damage a septic field by clogging its pipes, and against the use of plastics, pavers, or anything else that blocks both the transpiration/evaporation function of the drainfield beds (disposal of some effluent by evaporation)

and also that would block the movement of oxygen into the soil (absence of oxygen means that the necessary bacterial action on sewage effluent cannot take place, and in turn that means that the drainfield cannot work and that it will send pathogens into the environment including the aquifer - peeing in the water supply so to speak.

Plastic weed barriers would be an example of such a product that should not be used over a drainfield.

Plastic's effect on a soakbed or leach field (or drainfield) is discussed as well at SEPTIC DRAINFIELD FAILURE CAUSES https://inspectapedia.com/septic/Leach_Field_Failure_Causes.php

Excerpt: Don't seal the drainfield or soakaway bed top from contact with air by leaving a plastic liner of any sort - ice rink, swimming pool, tents and tarps in place. Don't seal the drainfield or soakaway bed top from contact with air by leaving a plastic liner of any sort - ice rink, swimming pool, tents and tarps in place.

Any strategy for removing weeds anywhere on a property should consider the effect of use of chemicals or weed killers on the environment. That means that some weeds are removed by removing the offending plants and where you use an herbicide you should research its effects as well as, of course, following the manufacturer's directions.

On 2018-07-03 by AJ

Thank You for responding promptly. I did not see the article you mentioned. Now i know.

For all kind of weeds growing on the drainfield, should i just pull them out or give up and let them run amok? It looks terrible.

Thank you,
AJ

On 2018-07-03 1 by (mod) -

With the apology that I can only answer conceptually because I can't see your weeds nor do I know the construction of your drain field, the worry would be plants who send roots down deep enough to invade the absorption bed trenches and piping.

I suspect that most surface weeds are not a problem and I would just mow them when I cut my grass. If you wanted to be scientific about it or do the sort of experiment that I might try, you could pull out or dig up a couple of the most ugly looking or larger weed plants or other plants over the drainfield and take a look at the depth of their roots.

If you thought that was not deep enough to invade the drainfield trenches you wouldn't worry about them.

On 2018-07-09 by (mod) -

Makes sense to clear everything but grass. Also looks pretty close to those trees.

On 2018-06-05 by Elizabeth -Calamagrostis x acutiflora OK over the septic?

Can feather reed grass be planted over a sceptic field
Calamagrostis x acutiflora also Festival glaucoma Elijah Blue
I wanted to use 2ground covers vinca and creeping Jenny any problems?

On 2018-06-06 by (mod) -

Feather reed grass ( Calamagrostis x acutiflora ) typical root depth is about 12 inches. If your septic field trench gravel top is 24 inches down you're probably ok.

On 2018-05-29 by Matt - OK to plant over abandoned septic field?

I have a septic system/drain field that is no longer in use for quite a few years. Am I still restricted on what I can plant on top of it? I would like to put a flowering ornamental fruit tree in the area of where it is but am not sure if it is okay.

On 2018-05-29 by (mod) -

Matt,

No, planting cosmetic plants is fine. If the home has been converted to a public sewer line, or if the currently-in-use septic absorption field is nowhere near the proposed tree site, and if there is no chance that someone is going to want to return to using this septic area (such as an alternating-bed septic design), then you can go ahead.

Watch out: I'd be a bit more careful about planting food crops on septic field soil if sewage-contaminated soil might be splashed up onto edible plants in rainy weather.

On 2018-05-13 by Terri - Why are plants over my drainfield dead?

I have a rose of sharon in the back yard. looks good the last few years. This year nothing, its all dead Also have hydrangeas did good for 2 years now dead this year.

Its over a drain field

On 2018-05-13 by (mod) -

Terri

From what I have read a rose of sharon plant can fall prey to any of a number of plants diseases, insect pests, and more rarely overspray from certain chemicals biocides that might be used around home.

It doesn't seem likely that would be the relationship to the septic system that would be at fault unless the tree is in fact drawing water from sewage effluent that was overdosed in some type of antifreeze.

If your research finds that that is the case you need to be concerned that the septic system itself has been damaged by such chemicals.

On 2017-10-31 by Kim - OK to plant dogwood trees over the septic? How far away?

I want to plant a tree for some shade but I have a septic tank in my front yard. I have heard of dogwood trees but I live in zone 10 So I'm not sure what to do or what to plant or how far? please help

On 2018-05-13 by (mod) -

Kim

Dogwood trees are shallow root plants that rely mostly on surface water. So if you keep the tree a minimum of one preferably to Ultimate Branch diameters away from the drain field and septic tank you're probably fine. I would estimate that as 15 or 20 feet minimum distance. 30 would be better.

 

On 2017-10-13 by Stan G - OK to grow heather & heath over a raised bed septic system?

Can you grow heather and heath over a raised septic system

On 2017-10-13 by (mod) -

Stan,

My quick check shows that heather has a shallow root system - enabling it to grow over rocky surfaces. But depending on where you live the heather may not flourish if it's too dry;

So the answer is that most plant experts say "no problem - shallow roots", but I worry that with many normally shallow-root plants the plant might amend its behaviour and send roots deeper than normal, attracted by the unusual nutrients below, particularly if it's not getting enough water.

On 2017-04-12 by Terry Lefor - is Horsetail reed (Equisetum or family Equisetaceae) OK over the septic bed?

Hello, wondering about horsetail reed for perimeter fencing around my yard. the yard contains the septic bed. Does this grass have a far reaching root system? I understand it is fairly invasive and can take over the garden if not pruned properly.

On 2017-04-12 by (mod) -

Terry, Horsetail reed (Equisetum or family Equisetaceae of which there are about 20 species) uses a deep root system, extending several feet into the soil or deeper and extending horizontally as well.

Also known as "Scouring rush" the plant is described by horticulturists as one that's therefore difficult to control or remove - just as you suggest.

I'd be afraid to plant it closer than 50 feet to a septic drainfield.

On 2017-03-24 by Anna - List of native flowers that are safe to plant over the septic drainfield

How about a list of native flowers which are ok to be planted over the septic field? It would be so helpful!

On 2017-03-24 by (mod) -

Anna

Thanks for the suggestion. "Native" flowers will be native or not depending on where you live.

But most flowers do not have long-deep root systems that would make me worry about root damage to the septic soakbeds.

Planting flowers over a soakbed or septic field for pure enjoyment is fine - I'll research and list any deep-rooting exceptions here.

However I would be concerned if you plan to cut and harvest and give-away or sell septic field-grown flowers if the flowers are planted in an area where they may be wet by an aerobic septic effluent spray system or by pathogen-contaminated soils in an area where a septic soakaway bed has failed, sending sewage effluent to the surface.

Native or Wildflowers to Keep Off of Septic Areas

Since the list of wildflowers is huge, and since it varies by where you live I"ve suggested that most wildflowers are fine to plant over or near septics within the constraints I suggested above.

So I'll just list exceptions: flowers to keep off of the septic area. Some plants are considered weeds in some areas and valuable plants or flowers in other areas - again it depends on where you live. Readers are welcome to comment to add suggestions.

Bindweed (creeping jenny) - considered a pest, is a deep-rooted plant.

Canada thistle is a deep-rooted perennial to keep away from septics.

Dandelion should really not be on septic systems though I know they're ubiquitous.

Some Dandelions can produce an incredible taproot that is usually just about a half/meter in depth but it's roots can go to 10-15 feet (4.5 meters) - which explains why they're so hard to pull out.

Probably OK but at the edge:

Sagittaria latifolia produces an edible root that can be about 1/2 meter deep - just enough to begin to get attracted by the top of some soakbed trenches depending on trench depth.

 

On 2017-01-01 by Edna - We plant Purslane over the septic fields/tank to feed local deer.

what about purslane over the septic tank; since it grows as a weed, it would be no loss if we had to dig it up. And deer like to browse it, so I hope they enjoy it and we get to see them near our home in the woods!! Any advice?

On 2017-01-01 by (mod) -

Watch out: Deer over the septic tank - let's hope it has a sound solid concrete cover, not a rusting steel one, or you may find a deer IN the septic tank.

On 2016-05-02 by Anja - What does it mean if we're told to keep off of the grass because there's a septic tank?

Hi there!
I'm about to lease a Cafe with nice grounds around the main building, but I've been told no-one is to step on the grass because we have a septic tank... why is that? Do you know? Thank you!

On 2016-05-02 by (mod) - important safety warning

Anja,

Watch out: I can only GUESS that someone is worried that there is an old, unsafe septic tank, perhaps one with a home-made or rusted steel lid. If someone falls into a septic tank, most often they die. Quickly.

I would not lease such a property before finding out just what is installed, and making sure that the property is safe. In my opinion both property owner and leasee (you) could face liability if someone is injured.

It's one thing for an owner to tell you not to walk on the grass, and it's a different problem controlling where visitors to the property may walk. Meanwhile, if the question is one of safety, rope off the area and keep people away.

If the owner thinks that stepping on a (safe, secure, properly-installed) septic tank or walking over one is going to hurt the function of the septic system, she's mistaken.

If the owner thinks that the reason to keep off the grass is because the septic system is in failure - pushing sewage effluent to the ground surface, an unsanitary condition - then she's right: you do not want people visiting your cafe to be walking in sewage effluent.

If that's the problem I would not lease the property until the septic drainfield has been repaired or replaced.

On 2016-04-02 by BonBon - ok to plant septic near trees and can I plant fers over the mound?

We need a mound system installed. They want to put it near a large group of trees on top of a hill. Is it a problem if I plant ferns over the mound? How far away should trees be from a mound?

On 2016-04-02 by (mod) -

BonBon - I apologize: we've written so many articles on this (well I have) that it can be tough to find exactly what you need when landing on an InspectApedia page from the search engines.

IN the live article links on this page, you want to see TREES or SHRUBS OVER THE SEPTIC FIELD or TANK

The safe distance from septic fields for trees depends on the tree species.

Check the root depth for the fern species you want to plant.

Compare that to the distance from the soil top to the top of the actual gravel-trench that contains the nearest individual leach line in the mound system.

If you've got a foot or more between the root bottom and the trench top you're pretty safe for ferns.

Question: flowers at the septic field borders burn up

(Mar 5, 2014) BJ said:
Why do the flowers planted at the very end of a septic leach field eventually appear to have 'burned up' and what can be done to prevent this? Are there any particular flowers that will work better (perennials for sun)?

Reply:

BJ

Thanks for the question, but sorry, I don't know but I suspect that your drainfield is sending a higher concentration of nitrates and nitrites to its borders - which is common as the leach lines slope down towards their ends. Check the soil nitrate levels to see if they're out of bounds.

Thinking in an opposite direction, also check moisture levels; it would be odd but possible that at your property that area is just too dry for the plantings, OR the opposite could be the case - excessive septic effluent may contain detergents or something harmful to the flowers.

I can't recommend specific plants partly because it's not my expertise and partly because it would be risky to recommend something without inspecting and testing the soil in the area you describe.

Question: playing horseshoes over the septic leaching bed or soakbed

(June 23, 2014) Anonymous said:
I want to put in a horseshoe court and it may be over part of my septic leach bed.
My question: I have to drive two steel stakes about a foot down in two places. Will this damage my bed or make it not work?

Reply:

(June 23, 2014) (mod) said:
Anon you're probably OK, as I'd expect the septic soakaway bed or leachfield pipes to be more than 12" down in the soil. Certainly if you punch a hole in a pipe that's not good - breaking the pipe and inviting a leak.
If you can see the actual location of the trenches by noting the depression lines that often mark their path, be sure to locate your horseshoe court stakes between rather than over the trenches.

Older questions below commented off

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• SEPTIC TANK & SYSTEM CARE BASICS

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