Clumping and vining ground covers will establish much quicker if planted in prepared soil. However, you must be careful not to add too much soil over tree roots. You can add up to a maximum of 2 inches of a blended planting mix, comprised of 70 to 80 percent organic matter. We do not recommend tilling the soil under a shade tree to prepare the planting site.
One cubic yard of prepared planting mix will cover: 81 sq. ft. @ 4" depth 108 sq. ft. @ 3" depth 162 sq. ft. @ 2" depth 324 sq. ft. @ 1" depth. Keep the flower planting area out away from the trunk of the tree. Never place added soil or mulch against the bark of a tree. This creates a constant moist area and can cause rot on the bark, providing a great place for insect and disease to attack the tree. The irrigation needed to keep the flowering plants looking good may encourage rot among the tree roots. Consider the long-term value of the tree against the short-term value of the flowers.
For more detailed information on Planting Under Mature Trees, visit this University of Nebraska-Lincoln web site.
