Septic systems and tree roots: what the EPA and extension services say

This page reports what the named sources say. It is not advice for any property. The sources are American, and none of them is a rule for a particular property: the distances they print differ from one another, and the sources do not say which applies to a given site. Roots in sewer pipes rather than in a septic system are on the roots and drains page, and roots near foundations are on the roots and buildings page.

What the EPA leaflet says

The EPA leaflet on landscaping on and around a septic system calls the drainfield a vital part of the system. It says tree and shrub roots can grow into the drain lines, that heavy items such as cars and livestock can break the lines, and that strong roots and heavy items can make the drainfield fail, which makes the whole system fail. It lists things to keep off the drainfield area, among them decks and patios, driveways, sheds, swimming pools and vehicles. It names grass and low groundcovers as plants for the area, and says that shallow-rooted plants should be used because tree and shrub roots can clog and break the lines. It also advises against water-loving plants and trees. The leaflet is dated September 2014.

Distances the sources print

Source	What it says
UF/IFAS publication SL474, Landscaping on or near Septic Drain Fields	The publication says tree roots can spread to 2 to 3 times the canopy width, and it calls planting a large tree about 30 feet across within 20 feet of a drain field "a receipe for septic system failure" in the publication's own spelling. It cites a 2010 Clemson Extension publication for this. It lists planting trees or shrubs of any kind on or near the drain field among the things to avoid, and says drain field pipes can lie just a few inches under the soil.
UF/IFAS Extension Nassau County, question and answer post of July 19, 2017	The post says distances found online range from 20 feet (University of Minnesota) up to 100 feet (North Carolina State University), and suggests a distance in between for fruit trees. The post says roots grow 2 to 3 times the drip line, which it defines as the tips of the branches, and gives an example of a 10 foot branch with roots possibly reaching 20 to 60 feet.
University of Georgia Extension, Water at UGA post of April 4, 2023	The post gives as the general recommendation keeping trees and plants with aggressive roots away from septic and sewer lines, because the lines give roots a steady supply of water and nutrients. It names slow drainage, blockage and back ups into the house or business as the issues from roots getting into pipes.

The two Florida sources measure roots against different things. SL474 uses the width of the canopy, and the Nassau post uses the drip line, the tips of the branches. The Nassau post names two universities whose published distances sit 80 feet apart. None of the three pages says that a state or county health office sets the distance for a site.

Plants over the drain field

SL474 says only shallow-rooted plants are acceptable on or near a drain field, and that plants with large, deep, tap or woody roots can stop the system working and can damage it by growing into the pipes. It names turfgrasses as the most common and easiest to establish, says bamboo and pampas grass should not be planted because of deep, expansive roots, and says edible crops and vegetable gardens should not be on or near the tank or drain field. It adds that a wet drain field can be a sign of septic failure, so plants showing signs of too much water may mean an inspection is due.

Who to call

County Extension office, Florida: the UF/IFAS county office whose agent answers owners' questions about trees and septic tanks
University of Georgia Cooperative Extension: the Water at UGA pages on on-site waste treatment, including roots and septic lines
US EPA SepticSmart leaflet: the federal leaflet on landscaping around a drainfield
Hiring an arborist: how owners find and check a tree professional