Caring for, Pruning, and Fertilizing an Oak Tree Landscape

Place a layer of mulch under the canopy of the tree to cover the surface of the soil. Create a layer of fine mulch, up to 4 inches deep, around the tree but away from the trunk. Avoid large chunks of mulch, which retain too much water in the root system of the oak, causing root rot.

Avoid over-watering the area around an oak tree. The roots of an oak tree extend far beyond its canopy. This root protection zone, which is typically 1 1/2 times the size of the canopy, should be left in its natural state. The tree’s shallow root system sends out deeper horizontal roots to support the large tree and access water. Too much watering of the surface soil can weaken this root system.

Plant only native shade-tolerant plants that prefer dry soil under the tree’s canopy. Plant them at least 10 feet from the trunk of the tree. Water only enough to settle the new plants into the soil and then only when necessary. Avoid planting flowers, ground covers or grass that requires regular watering under oak trees.

Fertilize only if the foliage becomes pale or spotted. Use a fertilizer with nitrogen and apply a light dose once during the growing season. Native oak trees typically require no fertilizing. Mulching under the canopy eliminates the need for further fertilizing, as the wood mulch will provide adequate nutrients to the soil.

Prune oak trees only during the dormant winter months. Remove only dead or diseased branches or live limbs that are structurally unsound and can pose a danger. Do not cut off more than 10 percent of live limbs to avoid weakening the tree. Avoid thinning so many limbs that previously interior branches can be damaged by excessive exposure to wind or sun. Excessive pruning can lead to new growth that is prone to mildew, which will be detrimental to the continued healthy growth of the tree.

Avoid paving or cultivating areas within the tree's protective root zone. This area should be left undisturbed to avoid damage to the oak.