How to Make a Mound Around Trees

Dig the planting hold to a depth equal roughly two-thirds of the root ball height, and about two to three times the diameter of the root ball.

Set the soil aside and blend it with 50 percent finished compost, manure, leaf mold, or other organic amendments if you have very poor soil. It's actually best to allow trees to adapt to the native soil, but if the soil has very slow drainage and little nutrient content, some amendments are helpful. Reserve the amended soil for later use.

Set the tree in the planting hole so that up to one-third of the root ball rests above soil grade. Add or remove soil as needed from the bottom of the hole until the tree rests level and the trunk is vertical.

Hold the trunk upright while a helper back-fills the hole with the reserved, amended soil. Pack the soil gently to remove air pockets and ensure the tree stays upright. Fill the hole until the soil level is even with the surrounding soil grade.

Arrange garden hoses in a circle around the tree to outline the size needed for the soil mound. The soil mound should measure five times the diameter of the root ball. If the root ball measures 12 inches in diameter, the mound should measure 5 feet in diameter.

Build up a mound around the tree, using the amended soil, to fill in the space within the garden hose circle. Build up the mound with a gradual grade until you reach the top of the root ball. Do not pile soil on top of the root ball.

Cover the soil mound with a 3-inch layer of bark chip mulch to regulate soil temperature and retain moisture. Follow the same grade as the mounded soil. You can spread mulch on top of the root ball, but keep the mulch pulled back from the trunk by about 4 inches to avoid rot and infestation. The open space at the center gives the mulch a look similar to a doughnut.