8. Mulch your trees with about a 2 inch mound of pine bark or mulch of your choice. Pine bark or pine straw are great choices for evergreen trees because they like acidic soil and pine mulch adds acidity to the soil over time as it breaks down naturally. Your mound should cover the entire rootzone or extend out to the dripline of your tree, whichever is larger. Do not stack mulch up against the trunk of the tree. This can invite pests and disease. Pull mulch away from the trunk to allow for air flow.