Fertilizing Mature Trees: Do They Need It?

We often think of mature trees as being self-sufficient and not needing any additional care or fertilization. However, this is not always the case. While fertilizing mature trees can be beneficial, it’s important to do so properly to avoid damaging the trees. 

As a reputable arborist in Phoenix, our team at Tree Workers of Phoenix know that some mature trees need fertilizing. Here’s everything you need to know.

Nutrient Requirements for Trees

Trees usually get the nutrients and minerals they need to thrive when growing in their natural habitat. In non-natural habitats, like your backyard, you’ll need to create favorable conditions to help the trees flourish. 

Besides leaving leaves and other organic materials on the ground to decompose and release nutrients into the soil, you may need to fertilize the trees. A nutrient deficiency can prevent trees from reaching their full potential while making them more prone to diseases and infestations. 

The Agriculture Department of the University of Minnesota explains that nutrients that trees require for healthy growth fall into two broad categories:

  • Micronutrients: Trees require these nutrients in small amounts. They include iron, zinc, manganese, molybdenum, chlorine, boron, and copper. 
  • Macronutrients: Plants require them in larger amounts for growth. They include nitrogen, potassium, phosphorous, magnesium, calcium, sulfur, and magnesium. 

Adding macronutrients, particularly a few pounds of nitrogen, helps improve growth, whereas deficiencies can result in slower growth and unsightly symptoms. 

Fertilizing products usually provide trees with the right nutrients, and product labels indicate the percentage of nitrogen, phosphorous, and potassium that each product contains. 

Slow vs. First Release Fertilizer

Fast-release fertilizers come in handy when trees are in distress and require emergency attention. However, these fertilizers often disappear fast.

A slow-release fertilizer is often the best option for fertilizing mature trees. Instead of short, intense feeding, trees usually respond better to a slower, regulated release of nutrients over several months rather than weeks. 

When to Fertilize Mature Trees

It’s best to apply the recommended fertilizer between March and April to promote sufficient energy and growth throughout the tree’s growing seasons. 

How to Fertilize mature Trees

Different trees have different fertilization requirements. However, you can generally achieve great results with a simple surface application for trees growing in the forest, mulched, or in other similar environments. 

Simply spread the granular fertilizer on the surface evenly around the tree canopy’s edge. Avoid putting fertilizer within one foot of the tree trunk. If your trees grow in turf, apply the fertilizer beneath the grass root zone for the best results. 

Drill small holes eight to 12 inches deep, uniformly spaced around the drip line, and distribute the fertilizing product equally among the holes. Next, cover the holes. This technique keeps nutrients in the tree’s root zone, preventing fertilizer waste and burning the grass. 

Contact Us at Tree Workers of Phoenix Today

If you want to learn more about caring for trees, our Tree Workers of Phoenix professionals can help. Besides learning about fertilizing mature trees with liquid fertilizer, we can also help you learn all about tree shaping and other tree care practices. Contact us today at 602-320-2797 to request a free estimate.


Tree Workers of Phoenix has been in business since 1994 and is a member of the Better Business Bureau (BBB) and International Society of
Arboriculture (ISA).


18402 N. 19th Ave. #115

Phoenix, AZ 85023

Phone: 602-320-2797

Email : rickthetreeexpert@gmail.com

Hours of Operation :

Monday - Sunday : 9:00am-5:00pm


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