The most common mistakes when fertilizing trees

Trees need water, light, a suitable location, and nutrients. Therefore, it seems logical to fertilize a tree. However, not all fertilization is actually beneficial. Too much fertilizer can even harm a tree.

This article shows the most common mistakes when fertilizing trees and explains how to avoid them. You can also find the article... how to fertilize trees correctly.  

Table of Contents

• Mistake 1: Fertilizing without knowing the actual need
• Mistake 2: Using too much fertilizer
• Mistake 3: Fertilizing only the tree and forgetting the soil
• Mistake 4: Fertilizing at the wrong time
• Mistake 5: Applying fertilizer only directly to the trunk
• Mistake 6: Fertilizing without watering sufficiently
• Organic or mineral fertilizer?
• How to fertilize trees correctly

Mistake 1: Fertilizing without knowing the actual need

Should you fertilize the tree "just in case" because it seems a little weaker or the leaves are smaller than usual? Not every problem is caused by a lack of nutrients.

Drought stress, compacted soils, root damage, or unfavorable site conditions can cause symptoms similar to a nutrient deficiency. Therefore, it's worth taking a closer look first:

• Is the tree growing in a generally healthy way?
• Are the leaves developing normally?
• Were there any prolonged periods of drought?
• Is the soil strong compacted?
• Has there been any change to the location, for example due to construction work?
• How does the tree develop with additional watering?

We recommend a soil analysis if you plan to use a specific mineral fertilizer. Organic fertilizers such as worm compost, compost, bokashi, or mulch can usually be used without a prior soil analysis, as they have a gentler and longer-lasting effect.

Mistake 2: Using too much fertilizer

One of the most common mistakes is: more is better. However, this is rarely the case with trees. Excessive nutrient application can disrupt the natural balance in the soil. Some nutrients can inhibit each other's absorption. This can even lead to deficiency symptoms despite sufficient nutrient availability. 
The fine root tips, through which water and nutrients are absorbed, are particularly sensitive.

To put this in perspective: Trees grow slowly. They don't need large amounts of fertilizer in a short period of time. Often, moderate fertilization is much more sensible than a heavy application.

Mistake 3: Fertilizing only the tree and forgetting the soil

Many fertilizers primarily nourish the plant. However, the soil also plays a crucial role in healthy trees. Living soil contains:

• worms
• microorganisms
• mushrooms
• organic material

These soil organisms help make nutrients available and retain water. Therefore, it is often worthwhile to consider not only the tree's nutrient supply but also the soil structure. Organic materials such as compost, Mulch or  Worm compost This promotes soil structure and soil life in the long term.

Mistake 4: Fertilizing at the wrong time

The best time to fertilize is usually in spring. When the ground is frost-free and the tree begins its growth phase, it can make good use of the nutrients provided.

Problems often arise in late summer or autumn. Nitrogen-rich fertilizers can then stimulate new growth, even though the tree is already preparing for winter dormancy. The young shoots often don't have enough time to mature and can become susceptible to frost.

As a general rule, the main fertilization takes place between March and the end of May. After that, fertilization should be very sparing or targeted. You can find more information in our article. Trees fertilize themselves in the cycle of the seasons.. 

Mistake 5: Applying fertilizer only directly to the trunk

Applying fertilizer directly to the trunk seems logical at first, but this is usually not the area where the tree absorbs the nutrients. The actual absorption occurs primarily through the fine roots, which are often located in the outer part of the tree's crown. A large portion of the active root zone is often found where rainwater drips from the outer branches onto the ground.

Therefore, fertilizer should be applied as close as possible to the drip line and not directly on the trunk.

Mistake 6: Fertilizing without watering sufficiently

Plants can only absorb nutrients when they are dissolved in the soil. If the soil is dry, some of the fertilizer remains ineffective. Therefore, fertilization and irrigation go hand in hand.

Young trees especially benefit from thorough watering after fertilizing. This ensures that nutrients reach the root zone and can be absorbed more effectively. This is particularly important during extended dry periods. Therefore, soil moisture should always be checked before fertilizing.
In this article you will find more information about the Interaction of soil, nutrients and water. 

Organic or mineral fertilizer?

Both organic and mineral fertilizers can be used effectively. Mineral fertilizers usually work faster and provide nutrients directly in a readily available form. Organic fertilizers work more slowly but also promote:

• soil life
• the humus build-up
  
• water storage
  
• the soil structure

For many garden trees, organic fertilizers are therefore a good way to support both the tree and the soil. We recommend, for example, the use of... Worm compost. 

How to fertilize trees correctly

The most important recommendations at a glance:

• Fertilize only when there is a real need.
• It's better to fertilize moderately than excessively.
• Consider the soil, not just the tree.
• Prefer organic fertilizers
• Fertilize in spring
• Fertilize in the area of ​​the fine roots.
• Water thoroughly after fertilizing.

You can find more information in the article. how to fertilize trees correctly.