The Science Behind Fall Fertilization: Why It Matters for Your Trees

When most people think about fertilizing their trees, spring usually comes to mind. But for long-term tree health, fall is often the most effective season to apply fertilizer. While leaves are changing and dropping, the activity underground is just getting started.

What Trees Are Doing in the Fall

As temperatures cool and days shorten, trees enter dormancy above ground. However, their roots remain active well into late fall and early winter, as long as the soil is not frozen. During this period, trees focus their energy on:

• Expanding and strengthening root systems

• Storing carbohydrates for winter survival and spring growth

• Rebuilding nutrient reserves depleted from the growing season

Because of this shift in energy allocation, fertilization in the fall directly supports root development — the foundation of a healthy tree.

How Fertilization Supports Root Health

Many people associate fertilizer with high levels of nitrogen, phosphorus, and potassium (NPK). While these macronutrients are important in the right season, fall fertilization requires a different approach.

In the fall, applying too much nitrogen can actually stimulate unwanted new shoot growth — which is vulnerable to winter injury. Instead, our focus is on building soil health and root resilience.

That’s why our fall fertilization program uses blends rich in:

• Organic matter – improves soil structure, aeration, and water-holding capacity

• Beneficial microbes – support soil biology and help trees access bound nutrients naturally

• Micronutrients (such as iron, manganese, and zinc) – correct subtle deficiencies that impact foliage color, energy storage, and disease resistance

By enhancing the soil ecosystem rather than forcing top growth, we give trees the resources they need to strengthen their root systems, store energy, and prepare for the stresses of winter.

Benefits You’ll See Next Season

Fertilizing in the fall doesn’t usually produce immediate above-ground results, but the payoff comes the following year:

• More vibrant foliage and color in spring and fall

• Improved growth rates and canopy density

• Better resilience to drought, pests, and disease

• Longer lifespan and structural stability

  
  

Why Timing Is Critical in Northwest Indiana

Here in Northwest Indiana, soils are often compacted and nutrient-poor, especially in newly developed areas where topsoil is thin or removed. Fall fertilization helps correct these imbalances at a time when trees can best allocate energy to root growth.

Applying fertilizer too late (after the ground freezes) won’t provide the same benefits. That’s why scheduling applications in September through early November is ideal.

Click the button below to schedule your fall fertilization!

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