Plants, Septic and Failures

Many rural homes use private septic systems to handle household waste and are not hooked up to any municipal sewer system. When septic systems do not function properly, humans may come into contact with wastewater that contains disease organisms and other harmful substances. There also can be a significant cost to repair the system. Failure of the system can be caused by lack of proper maintenance, overuse of water in the household, or improper design of the septic system. But, another reason that can cause failure and should be of concern to home gardeners is the interference of plant roots in the system’s drainage leach field.

Possible indicators of a failing system includes a sulfur or rotten egg smell in the vicinity of the system or indoors, water and possibly solids surfacing in the lawn near the drainfield, or sewage backing up in the house.

Solids from the home septic system settle and build up in the septic tank, which should be cleaned periodically. The remaining water and finer material goes out into a drainfield so it can be absorbed down through the soil profile. If tree or shrub roots enter these drain tiles, they can clog up the system and cause backups or other failures, possibly even a replacement of the drainage system. Costs for drainfield replacement can often be several thousand dollars.

The standard recommendation of University of Illinois Extension Educators is to avoid planting anything above the septic tank or leach field. Care should also be taken to avoid plantings that are nearby enough to have roots enter the drain tiles. Not only can damage be done to the system, but there can be a potential high cost to move, remove, or replace trees and landscape plantings. Most local health officials also indicate not to plant near septic fields.

The Morton Arboretum in Lisle, IL has published a list of trees and shrubs that commonly invade septic systems and some that are less of a problem. Some common invaders on their list include red and silver maple, weeping willow, American elm, red cedar, forsythia, pussy willow, red-osier dogwood and others. Some that they indicate are less common invaders include sugar and Norway maple, white and green ash, white oak, and white pine, in addition to others. Again, though, the safest protection is to avoid planting on or near septic fields. Well designed and maintained septic systems will be trouble free for many years.

April - May 2004: Foolproof Perennials | Plants, Septic and Failures | Can I Prune Now? | Selecting Trees