While most root-killing products are approved in all states, some are not. Check the product label for suitability in your area and carefully follow label directions. Herbicide chemicals can be toxic; wear appropriate safety apparel such as goggles and work gloves while handling these products.
Homeowners rarely give a thought to the drain and sewer pipes snaking to and fro beneath their yards until the pipes break or get clogged by invading tree roots. Homeowner insurance plans often don’t cover damage to underground pipes caused by invasive roots. If you suspect a problem and need to fix it yourself, root-killing products — herbicides — are available to help, at least for awhile. Many root treatments kill small, “feeder” roots, but more of the same will likely show up eventually. Many tree species have far-reaching, deep or invasive roots that can cause problems with drain pipes. Roots generally cannot break drain pipes, but instead invade areas of the pipe that are already cracked or broken.
Contact herbicides formulated for root control in pipes kill only the roots they touches. Systemic herbicides are taken up by the roots and distributed throughout the offending plant, eventually killing it. Herbicides may be formulated with copper, dichlobenil or other chemicals, and may come in foam or granular (wettable powder) form. Some products require pre-mixing before you pour them into the drain pipes. In general, you should limit the flow of water into the treated drain pipe for several hours to allow maximum absorption of the herbicide.
Audrey Lynn has been a journalist and writer since 1974. She edited a weekly home-and-garden tabloid for her hometown newspaper and has regularly contributed to weekly and daily newspapers, as well as "Law and Order" magazine. A Hambidge Fellow, Lynn studied English at Columbus State University.
Herbicides for Killing Roots
Put on safety goggles, gloves, long pants and a long-sleeved shirt, and spray 1-foot-tall weed suckers with a ready-to-use systemic herbicide designed to kill brush. Coat all the suckers’ parts thoroughly. The 1-foot height ensures the suckers have enough surface area to receive a toxic dose of the herbicide. Examples of systemic herbicides designed to kill brush include solutions containing 18 percent glyphosate or 2 percent triclopyr.
Weeds block sewer lines when their roots grow inside the lines to search for moisture and nutrients, and often no sign of a problem appears until sewage overflows into the associated house. Blocked and leaking sewer lines also cause structural damage, offensive odors and contamination of the water table. In pipes partially blocked by weed roots, slow flow rates cause sewage deposits to build up within the lines. Woody weeds are the most likely ones to cause damage, and householders can dig them out or cut them down and then take measures to prevent their regrowth.
Check weekly for suckers growing from the weed roots. Suckers are above-ground shoots that grow from roots. They may appear away from the weed stumps, such as in the lawn or a garden border.
Dig out weeds along the sewer lines by using a garden fork, removing as many weed roots as possible. Alternatively, cut off the weeds close to the ground with pruning shears or a pruning saw.
Cover the weed root area or weed stumps with a 3- to 4-inch-thick layer of moist soil. Water the area regularly so that it remains moist.
Remove suckers when they have died, after a maximum time of four weeks. Spray suckers that are still alive with herbicide again.
Roots are a common problem in sewer pipes, which constitute a near-perfect hydroponic environment, and they can also become problematic in landscaping and other drain lines. An easy way to control them is to plant far from drains so that roots don’t ever reach the pipes. Once the roots are established in the pipes, however, you have two options. You can blast them out, using mechanical means, or you can treat them with chemicals.
Veil and Tail Roots
Drain-cleaning professionals have more than one root-killing chemical in thier arsenal. To be effective, the chemical must be non-systemic — it must kill the roots without harming the plants — and it must present an acceptably low contamination hazard. Plumbers often use a foam made of metam sodium and dichlobenil to kill tree roots in sewers. This combination is non-systemic, non-selective and effective, but the chemicals are classified as restricted use and aren’t available to the general public. One commercial product that substitutes another restricted-use chemical — sulfamic acid — for metam sodium presents a danger of groundwater contamination if used in permeable soil. Both products are for use by licensed professionals only.
Commercial Root-Control Chemicals
You’re most likely to have blockages in the drains if you have trees or woody shrubs growing in the vicinity. If there’s a steady flow in the drains, the plants will send veil roots through pipe joints or small fissures. These roots grow downward until they contact the water and create blockages whenever there’s a surge, such as during a rain storm. If flow is intermittent, on the other hand, tail roots enter from the top, bottom and sides and grow in the direction of the flow. They eventually grow large enough to permanently block the pipes.