Tree Fertilizers: When and How (Including The Best Tree Fertilizers)

Tree fertilizers are vital for providing fruit trees, evergreens, and deciduous trees with the nutrients they lack. The right type of fertilizer can help your trees grow larger, produce more fruit and foliage, and live longer. The best tree fertilizers ensure that trees in your garden continue to grow well and thrive for many years.

Before choosing to fertilize trees, it’s vital to consider if your trees need fertilizing. Trees that show signs of damage due to overwatering or disease may not benefit from adding extra nutrients. Additionally, if you decide to fertilize trees, you must use fertilizer in the correct amount, at the optimal time, and in the proper place.

It’s worth considering the benefits of using fertilizer for trees. After all, trees are an investment. They provide shade, shelter, beauty, and often fruit. Because trees can take years to reach maturity, it’s worthwhile taking care of them. Proper tree care requires regular watering, pruning, and, of course, fertilizing when needed.

This article is a complete guide to using tree fertilizers. You will find the answers to many questions regarding providing tree nutrients. You will learn about the best fertilizers for fruit trees and the best way to fertilize trees in your front or backyard.

Why You Should Use Tree Fertilizer

The primary reason you need to fertilize trees is to strengthen their overall health. Fertilizing trees helps develop new growth and ensures that roots remain healthy. Trees that grow healthy don’t succumb easily to pests, diseases, and other stressors. Fertilization provides the nutrients trees require for vigorous growth.

It’s a good idea to use fertilizer to help established trees continue to grow. However, young trees also benefit from appropriate fertilization to help them develop healthy roots. A regular application of fertilizer in spring and fall can help boost your trees’ health. Or, you could apply a slow-release fertilizer once a year.

Do You Need to Fertilize Evergreen Trees?

Evergreen trees can benefit from additional fertilization. You want to apply fertilizer to evergreens if soil quality is poor, needle growth is sparse, or you notice substantial insect damage. Additionally, some evergreens tend to grow slowly. So, fertilizing evergreen trees can bolster growth and help resist pests and disease.

Although evergreens require fewer nutrients than deciduous trees or fruit trees, they still need “feeding.” However, suppose your garden soil is acidic, and the conifers or evergreens look healthy. In that case, you can hold off applying fertilizer.

To decide if your evergreens need fertilizing, it’s good to test the soil pH. Typically, evergreen trees grow best in acidic soil. If the ground is too alkaline, nutrient uptake may be poor, and fertilization won’t provide the expected results on evergreens.

Tree Fertilizer vs. Tree Food

Tree fertilizer is not food for trees. Although it’s common to refer to fertilizing trees as feeding them, tree fertilizer is only nutrients and minerals. Trees produce food through photosynthesis—creating sugars that are vital for healthy foliage and growth. If the soil lacks minerals, then fertilizer can improve its quality.

The primary nutrients or minerals in soil required for growth are nitrogen (N), phosphorus (P), and potassium (K). Trees also need micronutrients to grow well—iron, zinc, boron, silicon, molybdenum, copper, and manganese.

You will notice that fertilizers have an NPK rating. This rating refers to the proportion of the three primary minerals in the fertilizer.

How to Decide If Your Tree Needs Fertilizer

Fertilizers can help trees have lush foliage, a robust root system, and produce flowers and fruit. However, providing trees with extra nutrients and minerals is not always necessary. Trees feed by the photosynthesis process. In some cases, soil quality is adequate for tree health, and no amendments are required.

How can you decide if you must add fertilizer for trees to improve soil quality? Here are a few handy tips:

Test the soil to determine if your tree needs fertilizer. Before buying tree fertilizer online or at a garden center, it’s usually a good idea to test the soil. A soil test measures the levels of nutrients and the soil pH level. This test will indicate if you need to fertilize trees to address mineral deficiencies.

Growth rate can indicate if fertilizer is necessary. Check your trees for signs of poor growth—yellowing leaves, smaller than standard leaf size, little new growth, or early leaf drop. Sometimes, poor growth is a nutrient issue. Other times, it could be related to overwatering, compacted soil, or external stressors.

When was the tree planted? Typically, young trees and newly transplanted trees benefit from additional fertilization after a couple of years. Slow-release tree fertilizers can help boost growth after the root system of new trees is established.

Where is the tree growing? Trees growing beside lawns that are fertilized rarely require separate fertilization. However, trees planted in sandy soil that lacks organic matter may need some extra nutrients to stay healthy.

Nutrients in Tree Fertilizer

The primary three tree-essential nutrients are nitrogen, phosphorus, and potassium, or NPK. Depending on the type of tree fertilizer you buy, there may also be significant amounts of calcium, sulfur, and magnesium. Additional micronutrients added to tree fertilizers include iron, zinc, copper, chloride, boron, copper, and molybdenum.

Here are reasons why nitrogen, phosphorus, and potassium are vital for trees:

Nitrogen (N)—This essential element helps with photosynthesis so the tree can create sugars for food. Nitrogen helps to develop lush, green foliage.

Phosphorus (P)—A vital nutrient to develop strong roots and make trees more resistant to disease. Phosphorus is the mineral that helps produce flowers, seeds, and fruit.

Potassium (K)—This crucial nutrient ensures trees produce healthy fruit and prevents damage during cold weather. Potassium helps make trees less vulnerable to disease and recover from sickness.

What is the Recommended Tree Fertilizer?

Typically, a balanced tree fertilizer is rich in nitrogen and has less phosphorus and potassium. Some common tree fertilizers have an NPK rating of 16-4-8, 12-4-8, or 12-6-6. The figures represent the percentage of nutrients in the fertilizer.

For example, a 16-4-8 tree fertilizer consists of 16 percent nitrogen, 4 percent phosphorus, and 8 percent potassium. Typically, nitrogen is the main ingredient because this tends to leech through the soil faster.

If a soil analysis detects nutrient deficiencies, you’ll have to buy a suitable tree fertilizer. For example, if there is low potassium, the recommended tree fertilizer would have an NPK of 10-8-15.

Common Types of Tree Fertilizers

Tree fertilizers come in two types—slow-release fertilizers and fast-release, also called water-soluble fertilizers.

The decision to use water-soluble fertilizers usually depends on the soil type. Typically, fast-release tree fertilizer moves quickly through loamy, sandy soil. This can result in trees not getting enough nutrients. As the name suggests, slow-release fertilizer gradually releases nitrogen, phosphorus, and potassium over many months.

Slow-Release Tree Fertilizer vs. Fast-Release Tree Fertilizer

Generally, it’s best to use slow-release fertilizers for trees. Tree fertilizers that gradually release nutrients result in better tree growth and minimize the risk of root burn caused by a mineral buildup. Additionally, applying less fertilizer means fewer chemicals leach into waterways, causing less impact on the environment.

In some cases, fast-release tree fertilizers are helpful for quick fixes to restore tree health. However, it’s vital to mix the liquid tree fertilizer as per the manufacturer’s instructions. It’s also good to remember that less fertilizer is better than applying too much. In this case, “less is definitely more.”

Natural Tree Fertilizer 

Natural tree fertilizers are helpful for organic gardens and to minimize the risk of water contamination. Typical natural fertilizers for trees include aged cow manure or composted sewage sludge. There are also several commercial natural fertilizers for trees and shrubs you can choose from.

One advantage of natural tree fertilizers is that they contain a wide range of micronutrients. Additionally, natural fertilizers are more balanced than synthetic ones, are better for soil structure, and don’t cause root burning.

It’s good to note that fertilizing trees with organic substances may not provide enough primary nutrients. So, you may need to apply more natural fertilizer to get an adequate amount of nutrients.

At the end of the article, you will find out about some excellent organic tree fertilizers that are safe to use and provide all the necessary nutrients your trees need.

How Much Tree Fertilizer to Apply

The amount of tree fertilizer to use depends on the root spread of the tree. Typically, trees can take between two and four pounds (0.9 – 1.8 kg) of actual nitrogen per 1,000 square feet (93 square meter) of root spread a year. The root area of most trees is 1.5 times the area of the tree’s canopy.

For slow-growing, larger trees, you can apply around one pound (0.45 kg) of nitrogen per year. For younger, fast-growing trees, between two and four pounds is ideal.

Follow the mixing instructions on the packaging to know how much fertilizer to apply.

How to Fertilize Trees

Direct fertilization is the most effective way to apply tree fertilizer. Use a drop-type spreader to cover the tree’s root zone area evenly. It is fine to scatter fertilizer over mulch. After spreading the fertilizer, water the ground sufficiently to allow the nutrients to seep through to the roots.

For example, if the tree’s crown is 8 ft. (2.4 m) wide, the root zone will be 12 ft. (3.6 m) around the trunk. This is 1.5 times the area of the tree’s canopy.

For lawn trees, you may not need to fertilize them because the tree’s roots benefit from indirect fertilization. The tree roots absorb nutrients from the lawn fertilizer that you apply to turfgrass.

Related reading: How to care for your lawn without chemicals.

How Much Tree Fertilizer To Use – Example

Healthy trees depend on getting the correct amount of nutrients. Before spreading fertilizer over the tree’s root zone, you need to know how much to apply. Here is a simple way to calculate the amount of fertilizer to use.

Recommended amounts of fertilizer are in pounds per 1,000 square feet (lbs. per sqft.) of root zone area. Considering that a tree’s canopy is round, it’s necessary to use Pi (3.14) in working out the square footage of the root zone.

Here is the simple calculation:

• Divide the diameter of the canopy by 2 to get the radius
• Multiply the result by itself (i.e., square the number)
• Multiply the squared number by 3.14 (π)

Let’s say that the canopy of your tree is 8 ft. across. To work out the square footage, here is the calculation:

• 8 ÷ 2 = 4
• 4 x 4 = 16
• 16 x π (3.14) = 50.24 sqft.

The amount of fertilizer you need depends on the NPK rating. For example, a 20 lbs. bag of 10-8-6 contains ten percent nitrogen. Ten percent of 20 lbs. is 2 lbs. Therefore, the entire pack contains 2 actual pounds of nitrogen.

The recommendation is to apply 2-4 pounds of nitrogen per 1000 sq ft. This means that for the tree in the example, you need to apply 0.1 – 0.2 pounds of nitrogen (50 sq ft. is 1/20 of 1000 sq ft. – so you will need to divide the original recommendation by 20).

When to Apply Tree Fertilizer (The Ideal Time to Apply Tree Fertilizer)

The best time to apply fertilizers to trees is in early spring or the fall. As a general rule, you should never fertilize trees in summer. The hot weather and lack of soil moisture make it impossible for trees to absorb nutrients. The appropriate fertilization time is just before or just after the growing season.

Fertilizing Trees in Spring: Spring fertilization helps to encourage new growth and ensures lush green foliage throughout the summer. Additionally, fertilizing trees in spring can help the tree grow healthy and be more resistant to disease.

Fertilizing Trees in Fall: Fertilizing trees in the fall is good for replenishing nutrients lost during hot summer months. Also, fall fertilization can help to keep roots strong during winter.

Fertilizing New Trees

Trees don’t need fertilization at the time of planting. For the fertilizers to be effective, the roots need a few years to get established. Generally, wait two or three years before fertilizing newly planted trees. However, it’s still necessary to get a soil test done to check for nutrient deficiencies.

The Best Tree Fertilizers

Let’s look at some of the best fertilizers for trees that you can buy online. The tree fertilizer reviews will also look at the pros and cons of each product to help you make an informed decision.

Jobe’s Tree Fertilizer Spikes

Tree fertilizer spikes with a slow-release formula mean that you can provide the right amount of nutrients at the right time. Jobe’s fertilizer spikes are ideal for all types of deciduous trees. Applying the fertilizer in early spring will keep your ornamental foliage trees healthy until the end of the growing season. Use for elm, birch, maple, poplar, oak, and most types of deciduous trees.

Jobe’s tree fertilizer spikes have an NPK rating of 16-4-4. Because you only have to drive the spikes into the ground, there’s no complicated measuring.

You can also buy Jobe’s tree spikes that are suitable for fertilizing fruit trees or evergreen conifers.

Pros:

• Encourage lush green foliage
• Excellent value for money
• Easy to determine how much tree fertilizer to apply
• Ideal for all types of deciduous trees

Cons: 

• The fertilizer spikes must be kept dry after opening

This fertilizer is available on Amazon.

Miracle-Gro Shake’ N Feed Flowering Trees and Shrubs

Miracle-Gro is a brand leader when it comes to effective tree and shrub fertilizers. The convenient tree fertilizer pellets last from spring until fall, constantly providing the root area with essential nutrients. Miracle-Gro tree fertilizer has an NPK rating of 18-6-12, ideal if the soil needs extra potassium.

Pros:

• High-quality tree fertilizer for a reasonable price
• Easy to apply, no measuring required
• Only contains natural ingredients

Cons: 

• A few people complained that the product has a foul odor.

This fertilizer is available on Amazon.

Espoma Tree-Tone Plant

Espoma Tree-Tone fertilizer for trees contains all the vital nutrients that deciduous trees require. You can also use this fertilizer for fruit trees. One of the advantages of this tree fertilizer is that it’s a 100 percent organic formula. Additionally, this type of fertilizer for trees reduces the risk of root burn, improves soil condition, and minimizes the risk of water contamination.

This all-natural tree fertilizer has an NPK formula of 6-3-2. You can use this formula to fertilize fruit trees such as apple, cherry, pear, and peach trees. Also, it is suitable for willow, walnut, oak, cypress, chestnut, and other deciduous trees.

One thing to consider is that applying this fertilizer for mature trees requires digging it into the ground. However, it’s an effective organic tree fertilizer.

Pros:

• Excellent results
• Reasonable price tag
• Natural formula suitable for organic gardening

Cons:

• Requires some digging around the root base to fertilize mature trees 

This fertilizer is available on Amazon.

Related articles:

• The Best Indoor Plant Fertilizers
• How to Use Calcium Nitrate Fertilizer to Grow Fruit and Veges
• The Best Organic Lawn Fertilizers