What is Tree Fertilization?

Property owners often have questions when it comes to tree fertilization. When should I fertilize? What should I use to fertilize? And even, should I fertilize at all?

Trees draw most of their nutrition from the soil. Fertilization is the process of adding nutrients to soil. Under ideal conditions, it is usually not necessary to fertilize. However, in Colorado’s dry climate, ideal conditions can be infrequent.

Tree Fertilization for Young and Mature Trees

Young and established trees typically don’t need fertilization. A young tree’s tender roots can be damaged if fertilizer is added to the planting hole and fertilizer doesn’t accelerate growth in young trees. Established trees’ roots spread far and wide and draw nutrients from a larger area.

For trees in the middle of life, fertilization is usually only recommended when growth appears to have slowed (less than six inches per year) or foliage is taking on a yellow color. Tree location should also be considered before fertilization. Nearby utility poles and lines and buildings often force a tree into stunted or misshapen growth and fertilization can’t fix that situation. Additionally, a soil test might be considered before fertilization. County and state extension offices can advise about optimum soil nutrient composition and how to test.

If it appears that fertilization can be of benefit, remember that too much fertilizer is never a good thing. High concentrations of nutrients can damage tree roots. Slow release fertilizer is more costly than fast release, but slow release is better for the tree. Weed and feed type products should be applied very carefully because herbicides can also damage tree roots.

Timing is also important when applying fertilizer. Application around the root zone (the circle the tree canopy makes on the ground) before budbreak in the spring and then in late summer is a general rule of thumb. But like all rules, there are exceptions. Check with an extension agency for specific application timing for particular trees.

Could you use some help figuring out if and when tree fertilization should be done? Call SprayTech, Colorado tree specialists at 720-248-0000.