Establishing a vegetative cover, such as native grasses, is beneficial to the proper function of your septic system and critical for mound systems. Plants with good root systems can stabilize the soil to prevent erosion, loosen the soil to allow air movement, and even draw water. While trees and some shrubs can remove a significant amount of water from the area, their roots can occlude sewer lines, damage septic tanks, and invade distribution lines. Aggressive water-loving trees such as poplar, willow and maple should be avoided near the soil absorption field. Most trees root systems are about the same size as the leaf canopy at maturity. A good rule of thumb is to plant trees at least this distance away. Even if you plant non-aggressive types, the potential for damage to the system exists. Before planting trees or shrubs, consult with a tree nursery professional or Purdue Cooperative Extension agent.