Fertilizing Mulberry Trees: Timing, Products & Techniques

Although mulberry trees are typically low maintenance and able to withstand tough conditions, they still need vital nutrients in order to flourish and grow properly, just like any other plant.

Proper fertilization plays a vital role in ensuring the health and productivity of mulberry trees.

In this guide, you’ll find everything you need to know about the nutrient requirements of mulberry trees, the best fertilizers to use, when and how to fertilize them, and additional complementary practices to enhance their overall growth.

Key Takeaways

  • Mulberry trees require nitrogen, phosphorus, and potassium along with secondary nutrients and trace elements for growth and fruit production.
  • Organic and slow-release fertilizers are beneficial for soil health and a steady nutrient supply.
  • Recommended organic fertilizers include Down to Earth Organic Fruit Tree Fertilizer, Dr. Earth Natural Wonder Fruit Tree Fertilizer, and Espoma Organic Tree-Tone.
  • Proper timing, application techniques, and complementary practices like mulching and watering, optimize fertilization results for healthy and fruitful mulberry trees.

If you want to keep your mulberry tree in top shape and highly productive, mastering its basic care is vital. Explore my comprehensive guide, Mulberry Tree Care and Maintenance, to see where your care routine could be improved.

Mulberry Tree Nutrient Requirements

Although there are different types of mulberry trees, such as black mulberry trees (Morus nigra), white mulberry trees (Morus alba), and red mulberry trees (Morus rubra), they all require the same basic nutrients to grow and produce delicious fruit.

To flourish, mulberry trees require three primary nutrients, often referred to as NPK, along with other essential elements.

These are:

  • Nitrogen (N): Nitrogen is crucial for overall growth and helps in the formation of leaves, stems, and branches. It is essential for vibrant green foliage and plays a significant role in the tree’s photosynthesis process.
  • Phosphorus (P): Phosphorus is necessary for root development, flowering, and fruit production. It aids in energy transfer within the plant and is vital during the initial stages of growth and fruit setting.
  • Potassium (K): Potassium is essential for overall tree health, disease resistance, and the proper functioning of various physiological processes. It enhances the tree’s ability to withstand stress, such as extreme temperatures or drought.

In addition to these primary nutrients, both native and non-native mulberry trees also require secondary nutrients like calcium, magnesium, and sulfur as well as trace elements like iron, zinc, manganese, and copper.

Choosing the Right Fertilizers

When it comes to fertilizing mulberry trees, choosing the right type of fertilizer is essential to provide the necessary nutrients in the correct proportions.

There are two main categories of fertilizers: organic and synthetic. Each type has advantages and disadvantages.

Organic vs. Synthetic Fertilizers: Pros and Cons

Organic fertilizers are derived from natural sources, such as plant matter, animal waste, and mineral deposits. They are rich in organic matter, which improves soil structure and fertility over time.

Organic fertilizers release nutrients slowly and provide a steady supply of essential elements to the tree. They also enhance soil microorganisms, promoting a healthy and balanced soil ecosystem.

However, organic fertilizers may have lower nutrient concentrations and can take longer to show visible results.

Synthetic or inorganic fertilizers are manufactured chemically, providing nutrients in a concentrated and readily available form. They often have higher NPK ratios, allowing for faster growth and visible results.

Synthetic fertilizers are convenient to use and allow precise control over nutrient application. However, they do not improve soil structure and can lead to nutrient imbalances over time if overused.

Understanding NPK Ratios

Fertilizer labels display NPK ratios, representing the percentage of nitrogen (N), phosphorus (P), and potassium (K) present in the product.

For example, a common NPK ratio might be 10-10-10, indicating that the fertilizer contains 10% nitrogen, 10% phosphorus, and 10% potassium by weight.

The rest of the product is typically filler material or other micronutrients.

The appropriate NPK ratio for mulberry trees can vary depending on their age and specific needs.

Generally, a balanced fertilizer with equal or slightly higher amounts of nitrogen and potassium (e.g., 10-10-10 or 12-12-12) is suitable for mature mulberry trees.

Slow-Release vs. Quick-Release Fertilizers

Fertilizers are also categorized based on their release rates.

Slow-release fertilizers gradually release nutrients over an extended period, providing a steady supply to the tree.

They are particularly beneficial for reducing the risk of nutrient leaching and minimizing the frequency of applications.

Quick-release fertilizers provide an immediate boost of nutrients to the tree, making them useful when rapid results are desired.

Recommended Fertilizer for Mulberry Trees

Choosing the right kind of fertilizer can be overwhelming given the wide range of options available in the market. However, several trusted fertilizers are well-suited for mulberry trees:

  • Down to Earth Organic Fruit Tree Fertilizer: This organic granular fertilizer is specifically formulated for fruit trees, including mulberry trees. It has a balanced NPK ratio and contains beneficial microorganisms to enhance soil health.
  • Dr. Earth Natural Wonder Fruit Tree Fertilizer: Another excellent organic option, this fertilizer is OMRI-listed, meaning it is approved for organic gardening. It includes mycorrhizae and beneficial microbes to improve nutrient uptake.
  • Espoma Organic Tree-Tone: This pelletized organic fertilizer is rich in nutrients and contains beneficial bacteria and fungi to support healthy root development.

Before applying any fertilizer, it is essential to read and follow the manufacturer’s instructions for proper usage and dosage.

Best Times to Fertilize Mulberry Trees

Fertilizing mulberry trees at the right time is crucial to maximize the effectiveness of the nutrients and support the tree’s growth and mulberry fruit production. The best times to apply fertilizer to mulberry trees are:

  • Early Spring: Applying fertilizer in late winter or early spring, when the tree is dormant and just before new growth begins, is an ideal time to boost the tree’s energy for the upcoming growing season. The nutrients provided by the fertilizer will support leaf development and early fruit setting.
  • Late Spring/Early Summer: A second application can be beneficial in late spring or early summer if using a slow-release fertilizer. This helps sustain the tree’s nutrient supply throughout the growing season.
  • Fall: Applying fertilizer in the fall helps prepare the tree for the coming winter and promotes root growth during the cooler months. However, avoid fertilizing too late in the season as new growth stimulated by the fertilizer may not harden off in time for winter.

Generally, one annual application in early spring will be sufficient, but if your soil is poor or your tree is struggling, additional applications can be beneficial.

Fertilization Techniques

You may not be aware of this, but there is more than one way to apply fertilizer. Let’s explore the top two methods.

Surface Application

Surface application is a common method for fertilizing mulberry trees. To apply fertilizer to the surface of the soil, follow these steps:

  1. Measure the Area: Determine the tree’s drip line, which is the area underneath the outermost branches. This is where the majority of the tree’s feeder roots are located.
  2. Spread the Fertilizer: Sprinkle the recommended amount of fertilizer evenly over the soil within the drip line. Avoid direct contact with the tree’s trunk to prevent potential burns.
  3. Water the Area: After applying the fertilizer, water the soil thoroughly. This helps the nutrients dissolve and reach the tree’s roots.

Deep Root Fertilization

Deep root fertilization involves injecting the fertilizer directly into the soil below the tree’s root system.

This technique allows the nutrients to reach the tree’s roots more effectively and is particularly useful in compacted soils or areas with poor drainage.

Deep root fertilization is commonly done using specialized equipment, but it can also be achieved using a soil needle like this one attached to a garden hose.

A person picking fresh mulberries by hand.

Complementary Fertilization Practices

Mulberry tree care is fairly easy, but the job is not quite done once the fertilizer has been applied.

The practices detailed below explain how to give your mulberry tree some extra TLC and get the most out of the nutrients you just provided.


Mulching around the base of the tree should become standard care for mulberry trees as it offers multiple benefits.

Organic mulches, such as wood chips, straw, or compost, can help retain soil moisture, regulate soil temperature by shading the roots, and suppress weed growth.

As these mulches break down, they add much organic matter to the soil, enriching it with nutrients.

Aim to provide a 2-3 inch layer of mulch around the tree’s base, but be sure you don’t pile it against the tree trunk to avoid problems with rot.

Organic Matter and Compost

Incorporating organic matter and compost into the soil around mulberry trees improves soil structure, increases nutrient availability, and supports beneficial soil organisms.

Compost can be applied as a top dressing, mixed into the soil under the canopy, or used as a mulch. 

Proper Watering

Adequate watering is essential to complement fertilization efforts.

Mulberry trees are fairly tolerant of drought, but they do require regular and consistent watering, especially during dry spells or when establishing young trees.

Proper watering helps nutrients move efficiently from the soil to the roots, ensuring the tree can make the most of the applied fertilizer.

Special Considerations for Young Mulberry Trees

Young mulberry trees and newly planted trees have different nutrient requirements than mature trees, so factor in the age of the tree before fertilizing.

To promote healthy growth, focus on fertilizers with a balanced NPK ratio, preferably with slightly higher phosphorus and potassium content.

Young trees also benefit from additional phosphorus to support root development and establishment.

It’s wise to conduct a comprehensive soil test before applying fertilizer so that you know exactly what your soil lacks. This can usually be done through your local county extension service.

When you’re applying fertilizer to young trees, take care to spread it evenly over the root zone, and avoid overfertilizing as excessive nutrients can harm the young roots.

Water the area thoroughly after fertilization to aid nutrient absorption.

Fertilizing Potted or Container-Grown Mulberry Trees

For mulberry trees growing in containers, regular fertilization is essential since nutrients in containers can be depleted more quickly than in the ground.

Use a balanced, slow-release fertilizer specifically formulated for fruit trees. Follow the manufacturer’s instructions for application and frequency to avoid overfertilizing or causing nutrient imbalances.

The Effects of Overfertilization

Overfertilizing a mulberry tree can have adverse effects on the entire tree.

Generous amounts of nitrogen, in particular, can lead to excessive vegetative growth at the expense of fruit production, which is something you want to avoid.

Additionally, overfertilization can cause nutrient imbalances, leading to deficiencies of other essential elements.

Overfertilized trees may exhibit signs such as yellowing leaves, scorched leaf margins, wilting, or increased susceptibility to pests and diseases.

It is crucial to apply fertilizers in moderation and to choose slow-release fertilizers that provide a steady and controlled release of nutrients.

Closing Thoughts

Providing proper care for a mulberry tree will ensure a nice harvest of tasty fruits and healthy growth each year. Fertilizing mulberry trees is essential for maintaining their health and promoting fruit production.

Understanding the nutrient requirements and choosing the right fertilizers are crucial steps in ensuring the tree’s overall well-being.

The more you know, the more confidence you’ll have when tending to your mulberry trees. Discover key tips for planting and transplanting next: