Benefits of tree fertilization

200 year old oak tree

Trees are an important part of the urban landscape, adding value and beauty to our homes. The addition of an annual tree fertilizing program is a great way to maintain the health and vigor of your trees. Tree fertilizer provides the 3 macronutrients required for growth and metabolic functions. Additionally healthy trees are more resilient to stress, diseases and pests.

In the natural setting trees live in perfect harmony with their environment.  Leaves and twigs breakdown on the forest floor, recycling the nutrients needed for growth.  In the urban landscape trees face a number of challenges.

Pin oak in a driveway island, there is limited root space and radiant heat from the asphalt

• The organic layer of black topsoil has been stripped away from the ground when new homes are built.

• There is no recycling of leaf litter, leaves and grass clippings are bagged and removed.

• The soil is subject to compaction from irrigation, foot traffic, and construction.

• High ph commonly seen in clay soils can cause micronutrients to be unavailable.

• Restricted root zones, trees planted near roads and buildings.

• Competition from turf grass and other shrubs.

• Heat and drought stress are more severe in the urban microclimate.

Benefits of fertilization

A healthy elm tree shows the benefits of fertilizing

• Supplements 3 macronutrients, Nitrogen, Phosphorus, and Potassium, essential for growth and metabolic activities.

• Non water soluble Nitrogen provides a slow feeding. Water soluble nitrogen commonly used in lawn fertilizer has a quick release and is prone to storm water runoff.

• More fine roots are found in soil where Nitrogen is present. Enabling trees to better uptake water and nutrients.

• Soil injection with a root feeder probe puts fertilizer below turf grass roots where trees benefit the most. Additionally there is some aeration from injection, lessening soil compaction.

• Can speed the recovery and wound closure of pruned trees.

• Young trees can grow and establish faster with annual fertilization.

The best time to fertilize your trees is in spring or fall.  Spring is a large growth period for trees.  During fall trees will absorb some of the nutrients before going dormant and will have the rest in place for spring growth.

Tree fertilization is an excellent component in maintaining the health of urban trees, providing nutrients for growth and minimizing stresses.  Cultural practices such as regular watering and pruning are also recommended.

River birch before and after leaf chlorosis treatment

Here is a before and after picture of a River birch we treated for chlorosis.  In this case we fertilized with a micronutrient trunk injection.  Then we established a maintenance program of soil applied fertilizer with the addition of chelated micronutrients Iron, Manganese and Sulfur.