6 Best Fertilizer for Magnolia Trees | How and When to Use

The elegant Magnolia is an ancient tree that has existed on Earth longer than the bees, who love its nourishing pollen and ambrosial nectar. 

Out of hundreds of species in the magnoliaceae family, only a handful grow in residential spaces. These can be either evergreen or deciduous and can range in height from a “dwarf” 8ft to a considerable 70ft.

In order to maintain lush foliage and the large, multi-hued, and fragrant flowers they’re known for, the best fertilizer for magnolias will be an important part of their care.

Best Magnolia Tree Fertilizers 

For effective ways to fertilize these antique bloomers, be sure to read all the way to the bottom. But, if you’re simply looking for the best fertilizer for magnolia trees, below are my picks for the 6 best performers that I tested on my own.

Down to Earth Organic Flower Fertilizer Mix 4-8-4 

Best Organic Pre-Flowering

Down to Earth Organic Flower Fertilizer Mix 4-8-4 

Ideal for use right at the start of the Magnolia growing season to encourage bud set and enable flowers to last longer.

2. Jacks Classic No.4 20-20-20 All Purpose Fertilizer 

Best All-Purpose Fertilizer

Jacks Classic 20-20-20 All Purpose Fertilizer 

Help get new Magnolia plantings established, especially when planted in nutrient-depleted soil with this water-soluble feed. Can be used for a wide variety of garden fertilizing requirements.

3. Shake 'N Feed Flowering Trees and Shrubs Plant Food 18-6-12 

Best Fertilizer Granules

Shake ‘N Feed Flowering Trees and Shrubs 18-6-12 

A granular feed that can be used once Magnolia flowering has finished. Works to enhance lush, long-lasting foliage and resistance to pests and diseases throughout the summer months.

Choosing the Best Fertilizer for Magnolia Trees 

To encourage branches, full of pastel, cup-like blossoms, the specific nutrient needs of these trees must be addressed. Magnolias are not considered heavy feeders, but grow best in fertile soil that’s consistently supplemented with a nitrogen-rich feed.

Thriving in hardiness zones 7-9, magnolias will often absorb phosphorus and potassium before nitrogen, in spring. Thus, the reason some varieties bloom before new foliage emerges. Once it does, more nitrogen is needed for healthy root, trunk, branch, and leaf growth.

In order for all this seasonal beauty to grow in a healthy, unforced way, a slow fertilizing approach will provide your magnolias with a steady flow of nutrients.

Pro Tip: While nitrogen is required more than other macronutrients, the more fertile your soil is, the less it will need. In this case, an equally balanced feed (like a 10-10-10 NPK) would be more appropriate. 

Magnolia Tree Fertilizer N-P-K Ratio 

Magnolias thrive when they have access to the right combination of nutrients. The best NPK will depend on the age of your tree, the variety, and soil condition.

Choosing the right NPK is easy when you understand what your trees need. Which is the right ratio of nutrients to supplement what your soil is offering, as determined by a quality soil test.

For example, a 18-6-12 NPK has 18% nitrogen, 6% phosphorus and 12% potassium. Every plant requires these nutrients for optimal health. Just in different ratios.

Nitrogen (N) – is a key component in chlorophyll formation, encouraging green color and the creation of plant food via photosynthesis. 

Phosphorus (P) – plays a major role in the growth and overall structure of trees. Promoting healthy root development and accelerated tree maturity.

Potassium (K) – drives the circulation of water, nutrients, and carbohydrates throughout plants, shrubs, and trees.  

Magnolia Soil pH and Nutrient Uptake 

The best soil pH for trees will vary between species. Many of them are quite tolerant of soils that range from alkaline to slightly acidic.

Yet, magnolias grow most successfully in an acidic pH between 5.0 and 6.0.  Testing the pH around your magnolia may prove advantageous. Especially if your tree is showing signs of deficiency, stress, or a lack of blooms.

When the pH is below 5.0, micronutrients become more mobile. Meaning they become too accessible and are absorbed in excess of what the tree needs. Above 6.0, nutrients get locked in place, in the soil, and are unable to reach roots. This issue inevitably leads to deficiencies and stunted growth problems within the trees. 

Granular Vs Liquid Fertilizer 

Slow-releasing, granular fertilizers are commonly preferred, over liquid options, as the best fertilizer type for magnolia trees.

Granules break down slowly, with the help of soil microbes, moisture availability, and soil temperature. Supplying the kind of consistent access to nutrients that magnolia trees need. And they can do so (depending on the brand) for the entire growing season.

Of course, it’s tempting to go for fast results, especially if you live in a region with a short bloom season. But, large doses of liquid nutrients are absorbed quickly and usually all at one time. This can cause irreparable damage to your magnolia trees, considering how common accidental over-feeding is. 

That aside, liquid fertilizers do have their benefits. When magnolia saplings are planted in less-than-fertile soil, they immediately receive the nutrients they need to thrive. 

Even if you regularly use slow-release fertilizers, a quick boost of specific liquid nutrients may be needed during big growth spurts, to accommodate for any deficiencies, or in times of drought.  

Liquid Concentrate or Spray 

Liquid fertilizers come in concentrated, pre-mixed, or water-soluble granule forms. These carry nutrients directly to roots when used as a soil drench or in slow-drip irrigation systems. As a foliar spray, liquids can provide quick relief for chlorosis (yellowing leaves).  

Liquid feeds are often more economical and may show faster results. But, they don’t necessarily work better than slow-release options. 

Over-feeding is one of the most common causes of tree failure. This is especially so with liquids and could lead to root and foliage burn. So, caution is recommended with these, as is following exact manufacturer directions. 

Fertilizer Granules 

Granular fertilizers (both organic and synthetic) are easy to use and can provide consistent nourishment for up to nine months. Nutrients are released from each granule as warming temperatures slowly melt their coating away.

The biggest benefit to these is the gradual flow of nourishment to plant roots. Rather than inundating them with a blast of heavy nutrients all at once, when they don’t need it. 

Granules are applied by casting them evenly around the base of shrubs and plants. No watering is needed to activate them and is less likely to leach into nearby surfaces or groundwater. 

Fertilizer Spikes 

Spikes are highly convenient to use, especially if you have lots of potted trees. Pre-measured in various sizes, they’re easy to push into loamy soil and run little risk of burning.

The soil around mature magnolias tends to get compacted, making it difficult to insert spikes. A perk of spikes is that they can be broken up and evenly worked around large trees. Providing the same convenient nutrient flow. 

Nutrients are released from spikes by increased moisture and carry the added benefit of stimulating an increased resistance to disease and pests. Unused portions can then be stored mess-free. 

Organic vs Synthetic Fertilizers 

Deciding between organic and synthetic fertilizers for magnolia trees is simply a matter of personal preference and end-result expectations. However, an understanding of how each works and affects your environment can support an informed decision.

Organics are plant or animal-based and contain nutrient levels that mimic what would naturally be available in the wild. These options also increase soil fertility and nourish plants for longer, while encouraging proper aeration and drainage.

Synthetic fertilizers are mass-produced using minerals and chemical compounds. They can provide a big boost to branch and bud growth by providing higher levels of nutrients than plants would normally have access to. But, have little to no impact on healthy, microbial, soil activity, soil texture, or long-term fertility. 

Best Magnolia Tree Fertilizer Reviews 

Magnolias grow best in regions with warm summers and mild winters. But, it is possible to pot smaller varieties and winter them over indoors, in colder regions.

I have several different magnolias around my garden, so I’ve had the opportunity to test several different fertilizer options. The following are my picks for the top 6 performers, based on NPK results, versatility-of-use, and product features that can accommodate most soil types.  

Pros  

  • Effective on all flowering trees and plants
  • Formulated for vigorous growth, beautiful blooms, and healthy plant stock

Cons

  • May attract pets and wildlife with an organic smell

If you’re looking for something completely organic you can be sure you’re in safe hands with Down to Earth Flower Fertilizer. The NPK ratio of 4-8-4 makes this the perfect granular formula to use in Spring and before your Magnolia starts to bloom.

I have a collection of dwarf magnolias that I tested this on and within days, new buds appeared, and leaf shoots began to turn a darker, glossy green. I found that blooms seemed to last just that bit longer too.

How To Use: For new saplings, add ½-1 cup per hole, mix into the soil, and water in the well. For mature trees, side-dress ¼-½ cup per plant, once each month during the growing season.

Pros

  • Optimal nutrition for bud production and green foliage
  • Dissolves faster and cakes less than other top brands

Cons

  • It May give off an earthy odor 

These water-soluble granules from Jack’s Classic have become a popular choice for me in helping new magnolias become established. Especially in poor soil.

After planting a few new saplings, I tested this as both a soil drench and foliar spray. Within a few weeks, healthy root growth had begun. As was evident by more early blooms than I expected and lush, green leaves.

The versatility of Jacks Classic knows no bounds when it comes to practical feeding applications in and around the garden. It can be used as a fertilizer for vegetables, trees, shrubs, borders as well as pots. It’s my ‘go-to’ balanced feed that can be used all year long.

How To Use: Apply 1 tablespoon per gallon of water used. Repeat every 10-14 days.

Pros

  • New foliage and buds appear in just two days
  • Formulated to improve soil pH for neutral or acid-loving plants

Cons

  • It May result in burning if not watered in thoroughly

Miracle-Gro is one that I like to include in my tests, to see how it holds up to the competition. I shook this nitrogen-focused feed around my mature magnolia (one that I knew had a soil pH issue).

Before long, the foliage color became more vivid, and blooms increased. By adjusting the pH, my beautiful magnolia was now better able to absorb nutrients.

In addition to using this as a feed for aged Magnolia that tend to require more nitrogen, it can also be used to keep foliage greener and pest free once flowering has finished.

How To Use: For ground-planted shrubs, shake the recommended amount onto soil within the drip line. In pots: work up to 2 tbsp into the soil. Water both thoroughly after application. 

Pros

  • Contains patented probiotics for healthy soil
  • Certified organic by the OMRI

Cons

  • Pets may be attracted to it when used as a tea 

People and pet safe products give me a lot more confidence when letting my kids and dogs run around where I’ve fertilized. This is similar in application method to Miracle-Gro’s Shake and Feed. But, completely organic, with seven different types of beneficial microbes.

I tested this as both a tea and a slow-release on two different magnolia trees. While the organic smell of this attracted my dogs (and other wildlife), I got the same amazing foliage and bud growth on both.

How To Use:  Mix the recommended amount on the label into the soil around shrubs and water them well. Dosage will be specific to container size, plant size, and ground plantings.  

Pros

  • Beneficial NPK for well-composted soil
  • Fast growth in just one season

Cons

  • Not recommended for potted trees and shrubs 

This slow-release granular option from Scott’s performed really well on potted, dwarf magnolias that I have growing in well-composted soil. Alleviating my concern about too much nitrogen causing root burn.

The higher ratio of phosphorus and potassium increased the number of blooms on my dogwood and hydrangeas, as well as my dwarf trees. Win-win!

How To Use: 1 cup spread over every sq ft of the growing area within the drip line feeds for up to 2 months. Work granules into the top 3” of soil and water thoroughly.

Pros

  • Specially formulated to increase the number of flowers and fruit yield
  • Higher pH for acid-loving plants

Cons

  • May require a higher dose if applied to mulched soil.

An alternative to Dr. Earth granules, this Holly-Tone mix also contains beneficial microbes and a well-balanced NPK, and with added sulfur to balance out soil pH, this 4-3-4 formula really has it all. 

If that’s not enough, it’s also formulated to help increase tolerance to colder climates. This is certainly a plus, given that Magnolias typically grow in warmer climates. 

How To Use: For shrubs, 1 cup per foot of branch spread. For trees, 1 lb per inch of trunk diameter. Once in spring, then repeat at half the dosage in fall. 

How to Fertilize Magnolia Trees 

Magnolias are not heavy feeders. Yet, benefit from a gradual fertilizing approach. Using a slow-release fertilizer will provide mature trees with an effectively steady flow of nutrients.

Heavier feeding saplings may benefit from a faster-acting liquid that supports rapid growth, as they become established.

Too much, though, may result in forced growth that can result in weak branches that would be vulnerable to pests, disease, and frost damage. Magnolia trees, in general, grow healthier in form and color, when allowed to grow at a natural pace. 

Fertilizers with a higher percentage of nitrogen and ample amounts of phosphorus and potassium will encourage bountiful blooms, vibrant foliage, and a robust tree structure.

Naturally, each brand will have different instructions. However, when using granules, the recommended application rate is 1/10 lb for every inch of tree trunk diameter. Applying these just before a forecasted rainfall will hasten activation.

Liquid fertilizers should be applied using a watering can or a hose attachment, during the cooler hours of the day to prevent scorching. 

Avoiding Magnolia Tree Fertilizer Burn 

The most common cause of fertilizer burn is the over-application of it. That’s why it’s important to test your soil to make sure your magnolia actually needs it. Take trunk measurements to ensure you’re applying the most beneficial amount. 

Too much liquid nitrogen can burn roots when applied to the soil and leaves when sprayed. Too much potassium and phosphorus can leave excessive salts in the soil that will quickly absorb all available moisture, dehydrating your trees.

Symptoms of over-fertilization include:

  • A developing crust on the soil surface
  • Yellowing or wilting of branches and leaves
  • Out of season leaf/bud drop

If caught early, there are steps you can take to try and revive your magnolia tree. Remove the dying or wilting branches and leaves. Thoroughly water the area where you previously fertilized. Then, cover the root zone with mulch. 

When to Fertilize Magnolia Trees 

Magnolia trees experience a rapid surge of growth in spring, as they rouse from winter dormancy. Often putting out flowers before the foliage. Once foliage emerges, growth slows down a bit. To get the highest benefit from your fertilizer, you’ll want to apply it before, or just as new buds begin to appear.

If you feel your magnolia needs a second dose, apply it no later than mid-July. Slow-releasing fertilizers need time to take effect. Fertilizing any later than this will stimulate new growth that can be damaged by an early frost and leave the tree, as a whole, vulnerable. 

If it experiences summer drought stress, fertilizer should not be applied a second time. Roots, weakened by a lack of water, can become burned or shift into survival mode. Sending out new growth and blooms when it lacks the energy to do so.  

Another timing factor will be soil condition. For magnolias planted in sandy soil, splitting the applications has proven effective. Once in early spring and again in late spring. 

Fertilizing Magnolia Trees Pre-Blooming 

Applying fertilizer in early spring, just prior to the swelling of buds, will focus a proportional amount of your magnolia tree’s energy on the natural practice of producing abundant blossoms before the foliage. The balance will go toward lush greenery. 

Watering them well, at this time, is equally as important. Water allows nutrients to be better absorbed and circulated throughout the tree. Increased sunlight will also facilitate bud production. Keep this in mind when choosing a planting site.

Before fertilizing, it’s a good idea to test the soil to see what nutrients, if any, were depleted during the previous year. The result will give you the opportunity to adjust what you apply, to accommodate any revealed deficiencies. 

But, a lack of blooms may not indicate a problem. Some magnolia varieties don’t bloom until they’re at least three years old. Others wait until they’re 10 years old. 

How Often to Fertilize Magnolia Trees 

How often to fertilize will be dictated by the brand you choose, soil quality, and your tree’s age and size. Yet, because most fertilizers are made to accommodate several different plant types, make sure that the NPK will meet your magnolia-specific nutrient needs. 

Trees growing in fertile soil may not need any at all. Yet, when trees are hungry, the soil may become depleted of nutrients quickly.

In this case, mature trees will need their first dose of slow-release fertilizer, in spring, as buds begin to emerge. Dr. Earth’s organic granules require a follow-up application in 6-weeks. Miracle-Gro’s shake n’ feed option lasts for up to 3 months.

If you have nutrient-deficient soil that needs an immediate boost, Down to Earth’s organic flour mix or Jack’s Classic triple 20 works fast to provide tired trees with what they need to return to radiant health.

Verdict: Best Fertilizers for Magnolia Tree 

The verdict is in! The best magnolia fertilizer will primarily depend on soil quality and tree age. Magnolias benefit from a boost of phosphorus and potassium ahead of flowering, making Down to Earth Organic Fertilizer the perfect option right at the start of Spring. 

Down to Earth Organic Flower Fertilizer Mix 4-8-4 

Best Organic Pre-Flowering

1. Down to Earth Organic Flower Fertilizer Mix 4-8-4 

Ideal for use right at the start of the Magnolia growing season to encourage bud set and enable flowers to last longer.

For new plantings and where soil fertility is an issue, Jacks Classic All Purpose Fertilizer will help to fix nutrient deficiencies and encourage strong and healthy growth from your Magnolias.  

2. Jacks Classic No.4 20-20-20 All Purpose Fertilizer 

Best All-Purpose Fertilizer

2. Jacks Classic No.4 20-20-20 All Purpose Fertilizer 

Help get new Magnolia plantings established, especially when planted in nutrient-depleted soil with this water-soluble feed. Can be used for a wide variety of garden fertilizing requirements.

To see Magnolias through the rest of summer post-flowering, you need Miracle-Gro Shake N’ Feed. Working this into the soil will increase nitrogen and potassium availability to ensure healthy foliage and resistance to pests and diseases. 

If a bit more potassium is needed to boost nutrient and moisture circulation, then Espoma’s Holly-Tone granules will increase your chances of blooming success.

3. Shake 'N Feed Flowering Trees and Shrubs Plant Food 18-6-12 

Best Fertilizer Granules

3. Shake ‘N Feed Flowering Trees and Shrubs Plant Food 18-6-12 

A granular feed that can be used once Magnolia flowering has finished. Works to enhance lush, long-lasting foliage and resistance to pests and diseases throughout the summer months.

FAQ’s Fertilizing Magnolia Trees