Unusually green or soggy patches in your lawn can indicate a leaking or blocked sewer pipe underground, often caused by tree root intrusion. Common Causes of Blockages When to Call a Plumber: Drain and Sewer Warning Signs
If the DIY methods don't work, or if you're not comfortable attempting to clear the blockage yourself, it's time to call a professional: how to clear blocked sewer pipe
Here are some effective methods for clearing blocked sewer pipes: Unusually green or soggy patches in your lawn