Guide to Planting Over Septic System Components
Root depths of trees, shrubs, grasses & geotextiles & their impact on septic wastewater disposal fields

POST a QUESTION or COMMENT about planting grasses, shrubs, trees, or other ground covers over septic drainfields and near septic tanks

Which plants should be kept away from septic drainfields and which ones, generally shallow-rooted, are OK to plant in that area?

This article provides a table and other detalis describing the types of plants that should or should not be planted over or near septic fields or other septic system components.

Watch out: plants with invasive or deep roots can clog and ruin a septic drainfield, causing expensive damage that won't be fixed by simply running a root cleaner through the piping.

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

Photo of flower planting over a septic tank cover.

Based on both our own research and many years of septic failure investigations we've prepared this 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.

We will identifh just which trees, shrubs or grasses are ok to plant on or near septic tanks or soakbeds / leachfields and which are going to cause trouble.

We provide tables of acceptable plants and grasses around septic systems.

As we warned above, 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.

Also, 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.

Article Contents

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Guide to planting grasses, groundcovers, or flowers over septic drain fields or leaching beds

Many people have written to ask what can be planted over a septic field. Grasses, weeds, flower are OK: The best answer is grass or native grasses and weeds.

Flowers are ok so long as they are not varieties which send down deep roots. In the photograph above these relatively shallow-rooted flowers were set around a septic tank cleanout cover.

They won't cause any damage to the system. But when planning your planting arrangement for flowers over a septic tank, remember that if you plant valuable flowers too close to the access cover to a septic tank or distribution box, those plants may be damaged or destroyed when you have to excavate to open the tank or D-box cover.

Basically, any shallow-rooting planting will be fine to plant over the surface of or near septic tanks, distribution boxes, or septic drainfields.

The photograph abve shows typical grass and a few native wildflowers and dandelions growing in a lawn over a septic system drainfield at a Poughkeepsie New York home.

These plants are not likely to be harmful to the system, they stabilize the soils in the area, and they do not interfere with soil transpiration or evaporation.

Their roots are relatively shallow so these plants are not likely to invade the septic drainfield piping. Grass and native wildflowers are fine over the septic tank or drainfield, and also they are fine over septic mound systems.

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Grasses or Flowers or Groundcovers Recommended as Suitable for Planting Over / Near Evaporation-Transpiration Septic Systems

The following table of native (to New Zealand) or introduced species of grasses 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]

We have added Bermuda Grass and Kentucky Bluegrass widely used in the U.S. and some other countries.

Table of Grasses Suitable for Planting Over / Near Evaporation-Transpiration Septic Systems [3]
Common Name	Botanical Name	Comments
Common North American Short-Root Grasses
Bermuda grass		Typical root depth: 4-6 inches
Kentucky Bluegrass species		Typical root depth 6-8"
Red fescue		[2] 27.9 cm / 10.9 in root depth
Common New Zealand Grasses
Hooksedge	Uncinia Unciniata
Jointed twig sedge	Baumea Articulata	Carex Comans
Longwood tussock	Carex Comans
Oioi	Leptocarpus Similis
Pukio	Carex Secta
Toetoe	Cortaderia Fulvida	use native species to your area, not invasive pampas grass or other invasive species
Other Plantings that are Acceptable for Planting Over or Near a Septic Tank or Drainfield / Soakbed
Flowers, decorative		Shallow-rooted, [3]
Ivy		Shallow-rooted, [3]
Myrtle		[3]
Pachysandra		[3]

Notes to the table above

Sources

"Looking after your household sewerage system," New Plymouth District Council, Taranaki NZ, [3]
Brown, Rebecca Nelson, Cynthia Percivalle, Sophia Narkiewicz, and Samantha DeCuollo. "Relative rooting depths of native grasses and amenity grasses with potential for use on roadsides in New England." HortScience 45, no. 3 (2010): 393-400.
"J 1500 Series BAT® Media Plants with Model 952 UV Owners Manual", Jet Inc., 750 Alpha Dr., Cleveland OH 44143 USA, Tel: 440-461-2000, email: email@jetincorp.com Website: jetincorp.com - retrieved 2016/05/15, original source, Ohio health department, U.S.A., http://www.odh.ohio.gov/~/media/ODH/ASSETS/files/eh/sts/P-Jet-1500%20Series%20BAT%20Media%20Plants-Ownman-952%20UV

See BAT MEDIA SEPTIC PLANTS [web article] for details.
The company warns that because this type of septic treatment system requires regular inspections & service,

Do not position anything permanently over below-grade access covers. ... It is very important that the finished grade slope away from the plant. Also, grade must be at least below the bottom of the access covers. - Jet, Inc., Op. Cit.
Chase, Scott, SPOTLIGHT ON PLANTING OVER DRAINFIELDS - LANDSCAPING SEPTIC SYSTEM DRAINFIELDS AND MOUNDS [PDF], Washington State University Extension, Website: https://extension.wsu.edu/ (2014) retrieved 2018/07/02, original source: https://s3.wp.wsu.edu/uploads/sites/2144/2015/03/Spotlight-on-Planting-over-Septic-Drainfields.pdf
Glendon BioFilter LANDSCAPING AND PLANTINGS, [PDF] WSU Kitsap County Extension, Linger, F. & Tillery, P., 2011 glendon.com/docs/Landscape/GBT%20%20Landscape%20-%20WSU%20Compendium.pdf
U.S. EPA, PROPER LANDSCAPING ON & AROUND YOUR SEPTIC SYSTEM [PDF] (2015) U.S. Environmental Protection Agency, retrieved 2022/04/25 original source: https://www.epa.gov/sites/default/files/2015-06/documents/septicsmart-week-landscaping-final.pdf

Separately

at TREES OR SHRUBS NEAR SEPTIC SYSTEMS [web article] we provide a similar table of suitable trees or shrubs that can be planted near or in some cases on soakaway beds, drainfields, evapo-transpiration systems.

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Table of Grasses Not Recommended over Septic Fields

Table of Deep Root Grasses Not Recommended Over or Near Septic Fields or Soakbeds
Native & Ornamental Grasses	Typical Root Depth	Comments
Alkali grass	33.0 cm / 13 in	[2]
Big Bluestem	96" to nine feet [1]	Avoid over or near septic system fields & soakbeds or soakpits
Eastern bottlebrush	40.5 cm / 15 in.	[2] May be OK over deep septic fields
Indiangrass	73.7 cm / 29.0 in	[2] Avoid over or near septic system fields & soakbeds or soakpits
Little bluestem	64.6 cm / 25.4 in	[2] Avoid over or near septic system fields & soakbeds or soakpits
Switchgrass	70.9 cm / 20.9 in	[2] Avoid over or near septic system fields & soakbeds or soakpits
Smooth Brome	10-15" [1] 62.5 cm [2]	[1] May be OK over deep septic fields
Sideoats Grama	48" [1]	Avoid over or near septic system fields & soakbeds or soakpits

Notes & sources for the table above

Sources:

U.S. MN DNR, "Native Grasses - Soil Stabilization", Minnesota Department of Natural Resources, ret. 20 Sep 2015, original source: www.dnr.state.mn.us/roadsidesforwildlife/nativegrasses.html
Brown, Rebecca Nelson, Cynthia Percivalle, Sophia Narkiewicz, and Samantha DeCuollo. "Relative rooting depths of native grasses and amenity grasses with potential for use on roadsides in New England." HortScience 45, no. 3 (2010): 393-400.
Canadell, J., R. B. Jackson, J. B. Ehleringer, H. A. Mooney, O. E. Sala, and E-D. Schulze. "Maximum rooting depth of vegetation types at the global scale." Oecologia 108, no. 4 (1996): 583-595.
Abstract:
The depth at which plants are able to grow roots has important implications for the whole ecosystem hydrological balance, as well as for carbon and nutrient cycling. Here we summarize what we know about the maximum rooting depth of species belonging to the major terrestrial biomes. We found 290 observations of maximum rooting depth in the literature which covered 253 woody and herbaceous species.

Maximum rooting depth ranged from 0.3 m for some tundra species to 68 m for Boscia albitrunca in the central Kalahari; 194 species had roots at least 2 m deep, 50 species had roots at a depth of 5 m or more, and 22 species had roots as deep as 10 m or more.

The average for the globe was 4.6_+0.5 m. Maximum rooting depth by biome was 2.0+0.3 m for boreal forest, 2.1_+0.2 m for cropland, 9.5-+2.4 m for desert, 5.2-+0.8 m for sclerophyllous shrubland and forest, 3.9+0.4 m for temperate coniferous forest, 2.9_+0.2 m for temperate deciduous forest, 2.6_+0.2 m for temperate grassland, 3.7_+0.5 m for tropical deciduous forest, 7.3+2.8 m for tropical evergreen forest, 15.0_+5.4 m for tropical grassland/savanna, and 0.5_+0.1 m for tundra.

Grouping all the species across biomes (except croplands) by three basic functional groups: trees, shrubs, and herbaceous plants, the maximum rooting depth was 7.0_+1.2 m for trees, 5.1-+0.8 m for shrubs, and 2.6-+0.1 m for herbaceous plants.

These data show that deep root habits are quite common in woody and herbaceous species across most of the terrestrial biomes, far deeper than the traditional view has held up to now. This finding has important implications for a better understanding of ecosystem function and its application in developing ecosystem models.
Day, Susan D., and Ellen Silva, PLANTING ON YOUR SEPTIC DRAINFIELD [PDF] Virginia Cooperative Extension, Pub. 426-617, retrieved 2019/08/27 original source: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-617/426-617_pdf.pdf

Reader Question: what type of grasses are OK to plant over the septic fields in Northeast Florida?

Anonymous said:

Live in north east florida. What type of grass can I have planted over septic tank drain field?

Reply: List of deep vs shallow root grasses

Anon:

Grasses are generally OK as long as you're not planting something that sends down deep roots.

See the table earlier on this page where we list a variety of grasses whose root systems are generally not very deep. Bermuda grass roots go down 4-6 inches with some variation according to the type of soil.

Kentucky Bluegrass roots grow to a depth of 6-8". Either of those should be fine.
Native and ornamental grasses typically send roots down much deeper deeper.
Smooth Brome and Kentucky Bluegrass roots grow to about 10-15" of depth.
Sideoats Grama and Big Bluestem grasses can send roots down to as much as eight feet.

Stay away from these.

Watch out: whatever you are planting on or near a septic system, keep heavy equipment away from the septic tank and soakaway bed or leacfield.

See DRIVING OVER SEPTIC SYSTEMS for details.

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Using a Roto Rooter to Remove Roots from Sewer Lines and Septic Systems

Power augers or Roto Rooters™ for plumbing drains can be an effective way to remove a blockage or clog in a drain line.

But if your plumber shows you a tangle of roots when s/he pulls the augur back up the drain line, you should expect that additional repairs will be needed soon.

Even if you pull roots out of the blocked pipe section, the fact that they were in there means a tree, shrub, or other plant has invaded the area and its roots remain outside the just-un-clogged pipe.

You can count on the roots re-invading the pipe (and getting at those nutrients) soon. So de-rooting a clogged drain line is a temporary fix.

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Use of Geotextiles over Septic Drainfields

Several sources (citedvbelow) cite deliberate and advantageous use of geotextiles over a drainfield in order to help prevent penetration of and damage to the drainfield by the roots of landscaping plants installed above that level.

Some sources say such drainfield covers of geotextiles are an un-necessary expense - and I agree since we should be sticking to shallow-rooted plants over drainfields in the first place.

Other research of use of geotextiles within the drainfield itself as a filter or clog preventer gave mixed results as there can be issues with clogging of the fabric itself.

Photo: geotextiles covered with good soil installed below sod at this northern Minnesota home, described in more detail in
GEOTEXTILES & DRAINAGE MATS [live link just below] where we describe placement of geotextiles over a septic drainfield trench during drainfield construction.

Watch out: while the term "geotextiles" is used broadly, there are two very different categories of these synthetic fabrics, and the two should not be confused. Bothof the categories below may use synthetic frabrics, or geotextiles, but the individual fabrics have different properties and are intended for different uses.

In general, "geotextiles" or "geosynthetic fabrics" are man-made fabrics ( tyically the fabric is a polymer such as polyester, polyetlene, polypropylene, polyamide (i.e. nylon) or PVC polyvinyl chloride) and that are porous enough to allow water and air to pass through.

Difference Between Septic Drainfield Geotextiles & Landscape Geotextiles

Detiled definitions and properties of geotextiles are given in more detail in our GEOTEXTILES & DRAINAGE MATS article cited below.

Septic drainfield geotextiles or filter fabrics

are intended to act as a filter to prevent soil from washing down into and clogging the gravel fill in a conventional septic drainfield trench.

These geotextiles are placed over and sometimes around septic drainfield trenches during construction and are also might be used on the bottom of other alternative septic drainfield designs such as where chamber or "no-rock" gravelless septic systems are installed.

Watch out: Do not install non-woven weed barrier landscaping fabric over septic drainfield trenches.

Watch out: never install impermeable geotextiles or membranes over a septic drainfield, draifield trench, or mound system.

Impermeable membranes prevent the passage of water or moisture through the barrier - such products will prevenet proper septic drainfield operation by blocking transpiration: the movement of moisture through soil and into the atmosphere - one of the components of septic effluent dispersal.
Landscape geotextiles or barrier fabrics

are intended for use as a physical barrier, typically preventing root and plant growth into an area.

The two most-common uses of landscape geotextiles are to prevent weed invasion of a planted area and/or (usually in a more-coarse woven fabric form) as an erosion control cover to help hold soil in place.

Really? Our own tests at a New York property placed landscaping geotextiles over soil in an area intended to prevent spread of plants growing up from below.

We found that over a fifteen year period the plants that were placed atop the landscape geotextile sent roots down through it and some plants were also able to eventually penetrate the geotextile from below.

Still, properly-used, landscape geotextiles can work as a root barrier but in general, with proper plant selection, as a septic drainfield cover, landscape geotextiles should not be needed over a septic drainfield.

Research on Use of Geotextiles over Septic Drainfields

GEOTEXTILES & DRAINAGE MATS [web article] Geotextiles: types, uses, sources for building & site erosion, septics, drainage control
Abit, Sergio M. Jr., Ph.D., PLANTING on SEPTIC DRAINFIELDS [PDF] (2023) Ohio State University Extension, - retrieved 2023/08/06, origianl source: extension.okstate.edu/fact-sheets/planting-on-septic-system-drain-fields.html

Excerpt:

Plants are needed at the drain field. Plants take-up water,thuspreventing ponding of surface-applied effluentand promote infiltration of subsequent effluent applications.

They aid in the actual treatment of wastewater by absorbing plant nutrients and even some harmful dissolved contaminants.

Having plants on the surface will also enhance the development of soil physical properties that encourage infiltration and percolation of the wastewater.

In addition, plants promote a healthy community of soil microorganisms that aid in the treatment of the wastewater.

Equally important is the ability of the plants at the drain field to prevent soil erosion.

At a minimum, the drain field should be planted with a healthy cover of turfgrass that provide these important benefits.
Clemson C.E. LANDSCAPING OVER SEPTIC DRAIN FIELDS [PDF] Clemson Cooperative Extension, Home & Garden Information Center, Clemson Cooperative Extension, 103 Barre Hall Clemson, SC 29634, Clemson University, Clemson, South Carolina Tel: 864-986-4310 | 1-888-656-9988 (SC residents only) - retrieved 2023/08/06, original source: hgic.clemson.edu/factsheet/landscaping-over-septic-drain-fields/

Excerpt:

Strategies to Reduce the Threat of Root System Damage

...

There are also several root barriers to consider using. These can range from rudimentary materials to more expensive geotextiles that are impregnated with herbicides to restrict root growth. In order for the barrier to be effective, it needs to be buried up to a depth of at least 2 feet.

Ideally the barrier should run the length of the drain field to prevent tree roots from flanking the barrier and disturbing the drain lines. Keep the root barrier at least 5 feet or more from the drain line, and then at least another 5 feet from the planting hole.

Just remember to never create a circle around the root ball of the tree with the barrier, which would create problems for the tree as it grows.
Day, S.D. & E. Silva. 2013. PLANTING on YOUR SEPTIC DRAINFIELD [PDF] Virginia Cooperative Extension Publication 426-617 - retrieved 2023/08/06, original source: vtechworks.lib.vt.edu/bitstream/handle/10919/48282/426-617_pdf
Excerpt:
In general, shallow-rooted herbaceous plants that are not excessively water-loving are best. A leach field is a series of relatively shallow (a minimum of 6 inches below the surface) underground perforated pipes set in gravel trenches that allow septic tank effluent to drain over a large area.

As the effluent seeps into the ground, it is purified by the soil. Plant roots can help remove excess moisture and nutrients thereby making the purification of the remaining effluent more efficient. However, roots that clog or disrupt the pipes will seriously damage the drainage field.
|
The challenge of leach field gardening is to find plants that will meet your landscape needs but not clog the drain pipes.
Stanton, Kelly & Michael V. Mickelbart, P, LANDSCAPING OVER SEPTIC SYSTEMS WITH NATIVE PLANTS [PDF] Purdue University Department of Horticulture and Landscape Architecture; Brad Lee, Purdue University Department of Agronomy; and Don Jones, Purdue University Department of Agricultural and Biological Engineering, - retrieved 2023/08/06, original source: indiana.clearchoicescleanwater.org/wp-content/uploads/sites/3/2020/09/septic_landscaping.pdf

Excerpt:
Root barriers (for example, geotextile fabric impregnated with a longlasting herbicide) placed around the outside of the soil absorption field have the potential to prevent roots from invading trench drain pipes, however, installation is expensive and unnecessary with proper plant selection
The Natural Home (seller of geotextiles for septic systems) GEOTEXTILE SOIL FABRIC for SEPTIC SYSTEMS [PDF] - Email: service@TheNaturalHome.com Tel: 800-563-9720 & 970-262-6727 Web: henaturalhome.com/
U Minn, LANDSCAPING SEPTIC SYSTEMS [PDF] The publications can be ordered from the University of Minnesota Extension Service. Call (612) 624-4900 or (800)976-8636. For landscape design publications, refer to SULIS URL in Extension site: www.sustland.umn.edu. - retrieved 2023/08/06, original source: nesc.wvu.edu/files/d/766e3776-f192-43bc-8dd3-b95e263bc5a3/sfq_f02.pdf

Excerpt: Whether drainfields or mounds, Minnesota septic systems must have a minimum of three feet of unsaturated soil between the drainfield or point of infiltration and limiting soil condition such as hardpan, bedrock, or saturated soil in order to properly treat sewage.

A mound system is required if three feet of separation cannot be achieved with an inground trench system.
Yaman, Cevat, Joseph P. Martin, and Eyup Korkut. "Use of layered geotextiles to provide a substrate for biomass development in treatment of septic tank effluent prior to ground infiltration." Journal of environmental engineering 131, no. 12 (2005): 1667-1675.

Abstract

The use of layered geotextile filters for biological treatment of septic tank effluent prior to ground infiltration was investigated. The goal was to provide secondary treatment and prevent soil clogging by fostering biomass growth in the internal porosity of commercially available geotextiles.

The study used primary effluent from a water pollution control facility that serves a combined sewer area.

To identify sustainable operating conditions, the hydraulic loading rate (HLR) and other parameters were varied in tests with columns packed with multiple geotextile and granular layers.

At continuous high hydraulic loading rate application, over 90% of total suspended solids and biochemical oxygen demand was removed, but the three layer filters eventually clogged. When a 365L/m2day(9.0gal/ft2day) HLR was applied in dose and drain cycles to two filter layers, not only was there little loss in permeability, but ammonia (NH3) and nitrate (NO 3) concentrations in the effluent were reduced to below 5 and 10mg, respectively.

Scanning electron microscope images showed that the biomass morphology was not a continuous biofilm as was expected, but a discontinuous floc trapped within the geotextile pore structure. This provided intimate contact between substrate, oxygen, and biomass to produce the desired effluent quality and limited loss in filter permeability.

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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-06-04 by Anonymous - I want to plant roses in a bed along the edge of the drainfield

I am second owner of a home with a septic system and am new to having a drainfield. I want to plant roses in a bed along the edge of the drainfield as described in the plat drawings. I dug a hole for the rose bush that is 15 inches deep and about 18" wide.

At about 5 inches down, I encountered heavy clay with lots of small and large round stones 2" to 8" in diameter. In an effort to make digging easier, I filled the hole with water. After several hours, the water level has not dropped more than 1/2".

Is the poor percolation a requirement for the soil overlying a drainfield? Should I be concerned? Can I put 12" of good soil on top of the poor soil in raised beds or would this jeopardize the drainfield?

On 2021-06-04 by Inspectapedia Com Moderator - heavy clay in septic drainfield: can I add good soil and then plant stuff?

@Anonymous,

Soil that has poor percolation means that the size of the drain field will need to be increased in order to provide sufficient absorption into the ground. Let's hope that was done in the original design.

In the Article Index, see our article about

PLANTS OVER SEPTIC DRAINFIELDS

On 2021-01-19 by Janice - constant seepage from old septic (1960's) in the leach field.

Seem to have constant seepage from old septic (1960's) in the leach field. Got my lawn mower stuck in the muck. There is a huge maple tree within 20 feet of the tank and the land slopes towards the wet spot both from the house and side yard.

I was thinking of either adding a lot of soil to build a berm or planting vegetation that would help with the moisture evaporating. There is some sort of low green plant growing constantly even in winter but it is not enough for evaporation. Should I take down the maple and/or create the berm?

On 2021-01-21 - by (mod) -

It's best to divert surface runoff away from the drainfield, but adding soil over it can add to its failure to treat effluent by cutting oxygen.

I suspect your field has failed.

On 2021-01-21 by Anonymous

What should I do? Replace the whole field? What does that entail?

On 2021-01-21 by (mod) - constant seepage from old septic (1960's) in the leach field.

First, before we pour your money all over the ground, we need a reliable onsite diagnosis of the system.

That may involve a septic loading and dye test and either scoping the drainfield lines with a sewer camera (to rule out a less-costly failure like a clog or broken pipe) or a small bit of excavation of the wet end of a drainfield trench.

Take a look at the details found at SEPTIC DRAINFIELD FAILURE DIAGNOSIS

where you will also find more articles in our series on drainfield diagnosis, testing, and repair.

But for a fifty-year old drainfield that's wet, I'd not be very optimistic: most likely the field has failed and will need replacement.

On 2020-04-24 by AJ - recommendation on ornamental grass native to northeast?

Do you have any recommendation on ornamental grass native to northeast? i am planning to plant some 2 feet away from D box, not directly over the leach field.
Maiden grass keeps being recommended.

On 2020-05-03 - by (mod) -

AJ

In the article above on this page this table

Table of Grasses Suitable for Planting Over / Near Evaporation-Transpiration Septic Systems

should be of help

On 2020-04-19 by Greg - planting shade trees near (within 5 feet) of a passing sewer line?

What are your thoughts on planting shade trees near (within 5 feet) of a passing sewer line?

On 2020-04-20 by (mod) - planting shade trees near (within 5 feet) of a sewer line?

You might be okay planting a tree within 5 feet of a passing sewer line if the soil is stable and the tree roots are not aggressive.

Consider that an aggressive root under a line may heave it. And of course if there is ever over the remaining long life of the property a leak in the sewer line it will attract tree roots and become clogged and expensive. So yeah we may be okay but caveat cultor.

On 2019-11-04 by Mike - is Milkweed OK to plant over the septic leachfield?

Asclepias spp or milkweeds-has anyone planted these over leaching fields?

On 2019-11-04 by (mod) - is Milkweed Asclepias syriaca over the drainfield ok? NO!

Mike

I don't know if milkweed has been deliberately planted over septic fields but it certainly would volunteer to grow in such areas if given a chance. Let's both do some research to see what we can find on milkweed root depth as that will be a great answer to your question.

What I've found is a general statement that

the milkweed family (Asclepiadaceae) also called cottonweed, silkweed, Virginina silk, or wild cotton, sport a root system that includes a perennial crown and horizontal creeping roots - https://www.oardc.ohio-state.edu/weedguide/single_weed.php?id=70

But

Watch out: the same source on another page points out that

Roots can grow 13 feet deep and the length of horizontal roots can increase up to 10 feet in a single season.

Any plant that can send roots down 13 feet and creep horizontally 10 feet needs to be kept way more than 10 feet from the septic drainfield.

A related concern is that the milkweet seeds (each plant produces about 450 seeds in each pod) can drift for considerable distances and can survive for several years before germinating.

Bottom line: keep milkweed 50 or 100 feet away from your septic draifield.

COMMON MILKWEED (Asclepias syriaca), [PDF] Ohio Perennial and Biennial Weed Guide, Ohio State University, College of Food, Agricultural and Environmental Sciences, retrieved 2019/11/10, original source: https://www.oardc.ohio-state.edu/weedguide/single_weed.php?id=70

Excerpt:

Roots can grow 13 feet deep and the length of horizontal roots can increase up to 10 feet in a single season. A piece of root about 1 inch in length can produce a new plant. A common milkweed density of just over one shoot per square foot reduced wheat yields 47%.

On 2019-09-24 by Jeff Kennington - is a chestnut tree 30 ft from the septic tank a worry?

Just bought a house with a 22 year old concrete tank septic located about 20-30 feet from a chestnut tree that is probably about the same age. How concerned should I be? We like the tree, but should I have it removed?

Also, in terms of driving over the leach field pipes that are extending away from the tank

. I have had some vehicles drive over the field recently to do some contracting work. The biggest thing so far was a box truck. But I am also asking a 120c excavator to come in and do some work. Would a 30,000lb excavator or a dump truck driving over the field be a bad idea?

I don't think he will drive the dump truck/trailer/excavator of it together, but seperately and he will move quick as to not hang out on top. Am I asking for trouble?

Thank you,
Jeff

On 2019-09-27 by (mod) - I have had some vehicles drive over the field recently to do some contracting work.

Jeff

My best advice about driving over septics is at

DRIVING OVER SEPTIC SYSTEMS

Please take a look at that information as it's more complete than what I could write again off the cuff here.

Bottom line is that you might get away with driving over the septic system. A lot depends on the weather conditions and soil conditions such as humidity or moisture and of course details about how the drain field was installed.

If every trip over septic field destroyed it everyone will have figured out to never do that. However I certainly would not drive heavy equipment over a drain field. If there is no alternative than I would ask the contractor to put the insufficient plywood so it's just spread out the load and hope to not compact the soil and break pipes.

So please take a look at the article I recommend above and then don't hesitate to post follow-up questions and we'll be glad to take it from there

Continuing about the chestnut tree. That may be far enough away that it isn't an immediate concern.

On 2019-10-03 by Jeff - removed a fence to permit moving equipment without crossing drainfield

Thank you for the link. Just to play it safe, I removed a fence so that the equipment could drive over an area of the grass just past the drain field. Yes, life has taught me that absolutes are evasive

Best just to make informed decisions and be ready to live with the consequences if/when your schematics fail.

On 2019-10-03 by (mod)

Sounds smart and well worth the trouble. Removing and replacing a fence is a lot cheaper than having to replace the drainfield. I've often found a drainfield that had crushed pipes or impacted soil from people driving heavy equipment over it. The field may not fail right away but it often fails soon after such traffic.

On 2019-03-02 by Mark D Ward - mow or better, pull out and remove small trees & shrubs near or over the drainfield

Our leach feild is within a small pine forest. All the big trees above the field have been cleared. The ones on the perimeter are still there. There are hundreds if not thousands of small pine saplings coming up.

Do we need to cut them all down, use round up, or do we just need to keep them from getting to be mature trees? They are only about 6-8 inches tall and I believe most will die anyway.

On 2019-03-02 by (mod)

Mark I would mow small trees and other shrubs growing over the drainfield.

On 2018-09-08 by Janet - can I plant hydrangeas near my septic drain 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) - hydrangeas ok over septic drainfield

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.

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Guide to Planting Over Septic System Components
Root depths of trees, shrubs, grasses & geotextiles & their impact on septic wastewater disposal fields