If you have lived in an older home with mature trees, you know the havoc that tree roots can wreak on your sewer lines. If you have the opportunity to plan the planting of trees near the septic lines, there are ways to ensure the trees thrive without disturbing the septic tiles. A few trees that are recommended for areas with septic lines are beech, birch, cottonwood, hackberry, Norway maple, silver maple, spruce or sugar maple.
Dig holes a foot larger than the root ball in all directions and preferably 10 feet away from the sewer lines. Set the soil aside to add back later. You want to create a bed for the roots that will have all the nutrients they need so they don't grow toward the septic lines where concentrated nutrients are flowing.
Place a section of landscape root barrier at the bottom of the hole to keep the roots somewhat restricted from growing downward. Sometimes roots will grow around the barrier, but if you plant trees with shallow root systems, it should work well. The Grand River Forest Conservatory Authority lists the black cherry, the staghorn sumac and the red pine as types of trees that rarely clog field tiles in septic systems.
Mix a healthy amount of compost in with the reserved dirt and add a few shovelfuls to the hole. Spread the roots in the hole and add the rest of the soil, packing it in as you go. Water it well each week during the first year.
Mulch and fertilize the tree in an area as wide as the drip line. This will provide easily accessible food for the roots and keep them from reaching toward the sewer lines. Use a fertilizer monthly that is recommended for the type of tree you chose.
Replant new trees every eight to 10 years if you really want to be sure the roots don't spread down into your sewer lines. Of course, this shouldn't be necessary for smaller trees or shrubs.