Willow trees are members of the Salix genus and native primarily to temperate parts of the Northern Hemisphere. These trees are notable for their long, flexible branches and large fibrous roots, which allow these trees to survive in wet conditions. Willow roots are especially tough and tenacious and can cause problems for homeowners by blocking pipes and damaging foundations.
Willow tree roots seek moisture aggressively and will grow into and around drainage systems, pipes and foundations. Older ceramic and concrete pipes, which are more likely to leak, are at greater risk for willow root damage than newer PVC pipes, which tend to have tighter joints. Willow trees may also invade and damage septic systems and septic drainage fields. Never plant a willow tree close to the house or to water drainage systems.
Roots of willow trees often come to the surface, where they may sprout new shoots. These roots can be inconvenient for homeowners, as they interfere with mowing and lawn maintenance. Covering willow roots with a layer of mulch or topsoil can solve this problem. However, according to North Dakota State University, topsoil deeper than 18 to 24 inches may encourage fungal diseases and other tree-threatening problems.
Willow trees can survive even if some of their roots are cut. Cutting problem roots to reduce damage to a drain or foundation does not need to kill the tree. Willows do best when cuts are clean and straight, since jagged cuts can encourage infection. NDSU recommends using a saw or loppers to cut willow roots.
Willow trees sprout roots readily from above-ground portions of the plant, including branches. Cut branches in either summer or winter and root in water. Willow propagates readily, sometimes sprouting roots when the branch is still on the tree, and does not require rooting hormone to grow from a cutting. According to the Kansas Forest Service, willow cuttings root when the cut end is placed directly into the ground, quickly establishing a new tree.