This usually includes the soil up 1.5 to 2 times the diameter of the branch spread. Fertilizer applied to turf surrounding a tree will often supply most of the minerals required to keep the tree healthy. 12 to 14 inches deep every few years to compensate for nutrient mining and to get the fertilizer below the turf roots. When possible, chop leaves in place with a mulching mower, allowing the particles to filter down into the turf where the minerals they contain can be recycled. In general, large evergreen trees can be treated the same as deciduous trees with respect to fertilizing.
Evergreens normally have roots that extend beyond the branch spread.
Compost incorporated before planting, used as mulch around trees and shrubs or applied to turf as a top-dressing can supply the nutrients required to keep trees and shrubs growing well. Most composts are also good sources of calcium, P, K and micronutrients. In addition to supplying plant nutrients, top-dressing or amending with compost also adds organic matter to the soil, thereby improving soil structure, water infiltration and microbial activity. Bark mulches supply some calcium and potassium but are low in nitrogen and phosphorus. Ideally, soil test results should be used to determine fertilization rates, especially for phosphorus, potassium and micronutrients.