Trees and Septics
Tagged as: Septics
Tree root invasion of septic tank absorption fields, drop boxes, and tanks is a long-standing problem in the maintenance of on-site waste treatment systems. Many trees and shrubs readily invade these systems because they can provide air space, water, and nutrients. Trees and shrubs should not be planted on the mound, but can be grown at a distance. According to the University of Minnesota, most trees should be planted at least 20 feet from the mound, but trees with an invasive root system should not be planted within 50 feet of the septic system.
Listed here are a number of species and the likelihood of their roots invading septic systems. The list is not exhaustive, but includes those plants for which there is reliable information on the growth of roots and septic invasion. Check your local government for regulations specify- ing minimum tree setback distances from septic tanks and drain fields.
TREES WITH ROOTS COMMONLY INVADING SEPTIC SYSTEMS
| Boxelder | Acer negundo |
Red Maple |
Acer rubrum |
| Silver Maple |
Acer saccharinum |
| Red cedar | Juniperus virginiana |
| Cottonwood |
Populus deltoides |
| Weeping Willow | Salix alba 'Tristis' |
| Peachleaf Willow | Salix amygdaloides |
| Corkscrew Willow | Salix matsudana 'Tortuosa' |
| Black Willow | Salix nigra |
| American Elm |
Ulmus americana |
| Siberian Elm | Ulmus pumila |
| Slippery Elm | Ulmus rubra |
TREES WITH ROOTS RARELY INVADING SEPTIC SYSTEMS
| Norway Maple | Acer platanoides |
| Sugar Maple |
Acer saccharum |
| Red Pine | Pinus resinosa |
| White Pine |
Pinus strobus |
| White Oak |
Quercus alba |
| Bur Oak |
Quercus macrocarpa |
| Northern Red Oak |
Quercus rubra |
SHRUBS WITH ROOTS COMMONLY INVADING SEPTIC SYSTEMS
| Gray Dogwood |
Cornus racemosa |
| Red-osier Dogwood |
Cornus sericea ssp. sericea |
| Common Buckthorn | Rhamnus cathartica** |
| Pussy Willow | Salix discolor |
| Sandbar Willow | Salix interior |
**Buckthorn is an invasive plant that we do not recommend.
Herbaceous (non-woody) plants can be planted on the septic mound itself, but never plant edible plants on a mound or drainfield. Wildflowers and grasses are good choices for mound plantings. Not only do grasses provide year-round cover of the soil, but their fibrous root systems hold soil in place.