Oblique roots, also known as heart roots, are a type of tree root system that provides stability by forming a root ball filled with soil at the base of the trunk. The root ball acts as an anchor and a counterweight for the above-ground part of the tree. Oblique roots grow both downward and outward, and they have secondary roots that branch out from the primary ones. Oblique roots are more common in dry soil regions, such as the Mediterranean, but they can become unstable in wet soil or flood-prone areas. Some examples of trees with oblique roots are sycamore and red oak.