Is Fertilization for You?
Fertilization may not be for you. But when it is, you really need it.
The most important part of tree fertilization is a soil or plant tissue test before anything is applied. If you are not testing, you are guessing. And guessing with fertilizer is a good way to waste money or create new problems.
Trees make their own food using water, carbon dioxide, mineral elements, and sunlight. But they still need the right nutrients available in the soil. If essential elements are lacking, growth slows, stress tolerance drops, and the tree struggles to perform the way it should.
Trees require macronutrients:
Nitrogen, N
Phosphorus, P
Potassium, K
Calcium, Ca
Magnesium, Mg
Sulfur, S
They also require micronutrients in smaller amounts. Miss the balance, and you miss the mark.
Most urban soils are disturbed, compacted, scraped, or stripped of topsoil during construction. Then we rake and remove leaves every fall, which removes nutrients that would naturally cycle back into the root zone. Over time, that adds up. Slow growth or thin canopies may be tied to nutrient imbalance, compaction, or both. The only way to know is to test.
Spring and fall are generally the right times to fertilize. Nutrients applied then are available for the main flush of growth in spring. Trees will continue absorbing nutrients after the first freeze as long as the soil is not frozen. Summer fertilization is usually a bad idea. Fertilizer salts combined with heat and low moisture can stress trees. Late summer applications can also push tender growth that does not handle early freezes well.
Do not apply nitrogen at planting or after significant root damage. This will encourage top growth when roots are compromised.
If fertilization is warranted, it needs to be done correctly. At Wellnitz Tree Care, we use slow-release products and apply them across the entire root zone, either through soil injection or calibrated granular application.
Test first. Fix what is actually deficient. Leave the rest alone.
