Tree Fertilization 101: Why Spring is the Best Time to Feed Your Trees
- Austin Cowen
- Mar 31
- 3 min read
As trees emerge from dormancy in the spring, their demand for nutrients increases
dramatically. During this time, trees focus on developing new leaves, expanding root systems, and replenishing stored energy. However, many urban and suburban trees struggle to access the nutrients they need due to depleted soils, compaction, and competition from turfgrass.
Proper fertilization in spring enhances root development, improves canopy density, and increases a tree’s ability to resist pests, diseases, and environmental stressors. But fertilization isn’t a one-size-fits-all approach—understanding soil conditions, nutrient availability, and tree species requirements is essential.
Why Do Trees Need Fertilization?
In a forest, trees receive a steady supply of organic nutrients from decomposing plant
matter. In contrast, landscaped trees often grow in nutrient-deficient soil due to:
Leaf removal & lack of organic matter – Fallen leaves provide essential nutrients, but in urban settings, they are often raked and removed.
Soil compaction – High foot traffic, construction, and heavy machinery reduce soil pore space, limiting oxygen and nutrient uptake by roots.
Nutrient leaching – Rain and irrigation can wash essential minerals (like nitrogen and potassium) out of the soil, especially in sandy soils.
Grass competition – Turfgrass aggressively absorbs nutrients and water, leaving little available for tree roots.
Without adequate nutrition, trees may experience slowed growth, chlorotic (yellowing) leaves, weak structural development, and increased vulnerability to pests and disease.
Why is Spring the Best Time to Fertilize?
Spring fertilization aligns with a tree’s natural growth cycle, allowing nutrients to be
absorbed efficiently when they are most needed. Key benefits of spring fertilization include:
Stimulating root growth before summer stress – A balanced nutrient supply strengthens root systems, improving drought tolerance.
Supporting foliar development – Nutrients like nitrogen and magnesium enhance chlorophyll production, leading to greener, more vigorous leaves.
Building resilience against pests & disease – Trees under nutrient stress produce fewer defensive compounds, making them more susceptible to insect infestations and fungal pathogens.
While spring is ideal for most trees, timing and nutrient selection depend on species, soil type, and environmental conditions. Over-fertilization or improper nutrient balance can be just as harmful as nutrient deficiencies, leading to excessive top growth at the expense of root development or increasing susceptibility to disease.
How Do You Know If Your Tree Needs Fertilization?
While not all trees require supplemental nutrients, certain signs indicate deficiencies:
Slow or stunted growth – A tree growing less than expected for its species and age may lack key macronutrients.
Yellowing or pale leaves (Chlorosis) – Often due to nitrogen or iron deficiency, especially in high-pH (alkaline) soils.
Sparse canopy or premature leaf drop – A sign that the tree is struggling to maintain healthy foliage.
Poor wound healing or increased pest activity – Nutrient-deficient trees have weaker defense mechanisms.
How NWI ArborCare Can Help
At NWI ArborCare, we take a scientific approach to tree fertilization, ensuring trees receive the exact nutrients they need without overloading the soil. Our services include:
✔️ Soil Testing & Analysis – Identifying pH imbalances, nutrient deficiencies, and soil structure issues before applying fertilizers.
✔️ Deep Root Fertilization – Injecting liquid nutrients directly into the root zone, bypassing competition from turfgrass and improving uptake.
✔️ Customized Nutrient Blends – Using slow-release, bioavailable fertilizers tailored to your tree’s species and soil conditions.
✔️ Ongoing Tree Health Plans – Providing year-round monitoring and care to ensure long-term growth and resilience.
Fertilization is just one piece of the puzzle—healthy trees need proper watering, soil aeration, and pest management to thrive. Let’s give your trees the strong start they need this spring!
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