Crepe myrtles are easy-going trees that often thrive in poor-quality soil. When fertilizer is necessary, however, these trees respond best to balanced, low-concentration formulas.
While it rarely feels like the case, choosing the right fertilizer for any given plant species is pretty straightforward. The hardest part is sifting through the hundreds of formulas vying for your attention.
That’s exactly why I’ve put together a list of the best fertilizers for crepe myrtles along with comprehensive details of how and when to use them so you can get the best from your crepe myrtles each and every year.
So, rather than waste hours comparing various formulas, you can jump straight to using the best fertilizer for crepe myrtles and spend more time enjoying your garden!
Crepe Myrtle Fertilizer Quick Picks
Best Slow-Release Fertilizer
Miracle-Gro Shake ‘N Feed Plant Food 18-6-12
Perfect choice to get your Crepe Myrtle fertilizing off to a flying start at the beginning of the growing season. Can also be used as an all-purpose feed for many other trees and shrubs.
Best Fertilizer Spikes
Miracle-Gro Tree & Shrub Plant Food Spikes 15-5-10
Ideal for small or potted varieties or young Crepe Myrtle to support strong and vigorous root growth and protect against disease.
Best Top Dressing
Scotts Flowering Tree & Shrub Plant Food 11-7-7
Perfect choice for season-long Crepe Myrtle fertilizing that can also be used as an all-purpose feed for many other trees and shrubs.
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Choosing the Best Fertilizer for Crepe Myrtles
Crepe myrtle rely on nutrients in the soil to assist with the development of new growth in spring. Without sufficient nutrients, the production of flowers will be impacted if this new growth is delayed or hindered.
When fertilizing established crepe myrtles, I recommend applying a balanced tree and shrub formula in early spring, just before the growing season commences. A 18-6-12 or 15-5-10 NPK fertilizer is the best option as this contains high nitrogen to support new growth and high potassium to encourage strong flower production throughout spring and early summer.
For newly planted trees, I recommend applying a slow-release, balanced N-P-K, around 10-10-10 from the beginning of the first spring after planting and continue feeding every 6-8 weeks for the duration of the growing season. This will help to establish the root system as well as encouraging new growth and flowering.
Using a slow-release, granular fertilizer will reduce the temptation to overfertilize. This is something to avoid with Crepe myrtle since excessive feeding can trigger excessive growth, resulting in a reduction in blooms.
What is N-P-K Ratio
Plants can only thrive if they have access to nutrients. The three most important — known as macronutrients – are nitrogen, phosphorus, and potassium. These are listed on fertilizer labels as something called an N-P-K ratio and each has a specific role to play when it comes to the development of plants:
Nitrogen (N): Without nitrogen, plants would not be able to produce chlorophyll and consequently, photosynthesis would be impossible. Nitrogen enables plants to grow lush, green foliage and a healthy stem structure.
Phosphorus (P): Plants need phosphorus in order to store and distribute energy. If access to phosphorus is compromised, new tissue is unable to grow and cell division will not occur. It enables plants to form a healthy root structure and to develop flowers and fruits.
Potassium (K): Without sufficient potassium plants are unable to regulate water absorbtion and distrubtion. This macronutrient helps to protect plants against extreame drought and cold, improves their resiliance against disease and pest infectations and also ensures robust roots.
The amount of nutrients plants’ need depends on the species and also how much already exists in the soil in which they grow.
The N-P-K ratio is an easy way to tell how much of each macronutrient a fertilizer contains. For example, a 5-10-10 fertilizer contains 5% nitrogen, 10% phosphorus, and 10% potassium.
Ideal Soil pH for Crepe Myrtles
Crepe myrtles prefer soil that is slightly acidic — typically anywhere between 6.0 and 6.5 on the pH scale. Some varieties of Crepe myrtle can flourish in a soil pH as low as 5.0 so make sure you research the type you have before amending your soil.
Compounds such as sulfur or aluminum sulfate may be used to lower the soil’s pH and add more acidity. Conversely, I recommend using garden lime to raise soil pH if you need to make it more alkaline.
Whether your goal is to lower or raise the pH, the amendment is most effective when done before adding plants to the soil so always check soil pH with a soil test kit before you begin planting.
Granules Vs Liquid Fertilizer
The application method of your fertilizer type matters a great deal when it comes to how quickly the nutrients are released into the soil and how fast you want your trees to absorb nutrients.
Fast-Acting Liquids
Liquid Crepe Myrtle fertilizers are ideal for jump-starting your trees with a heavy dose of nutrition, especially if you have noticed a lack of growth in spring.
Liquid formulas are best used at the very start of the growing season and a good way to replace nutrients lost over winter. It’s fine to apply liquid fertilizer around the base of newly planted crepe myrtles or ailing trees and shrubs to aid in their establishment or bolster vitality.
Slow-Release Granules
Slow-release granules are my preferred fertilizer for crepe myrtles and many other ornamental trees in my garden.
Granules are easy — and economical — to distribute over a large surface area. This is perfect for covering the wide expanse of a mature crepe myrtle’s entire root system.
Slow-release granules also help ensure that your crepe myrtle is receiving a steady stream of nutrients throughout the growing season. And it’s easy to taper off applications as winter dormancy nears.
Fertilizer Spikes
Fertilizer spikes won’t do any harm to a large and well-established crepe myrtle. However, because they distribute nutrients to such a small section of the root system, and multiple spikes are often required for larger specimens, fertilizer spikes aren’t a very efficient option.
Save your fertilizer spikes for smaller container plantings, instead!
Organic Fertilizers
Organic fertilizers are similar to synthetic formulas, however rather than using chemical-based ingredients, they are made up of animal and plant-based compounds such as compost, manure, bone meal, and other natural materials. Esentially, they both contain the macronutrients nitrogen, phosphorus, potassium, plus other key nutrients.
Overall organic fertilizers are less damaging for the environment, cause less harm to wildlife, and will not contaminate water sources.
However, those that use organic fertilizers are intimately aware of the ‘natural’ odor that can accompany them and that can be highly attractive to pets. I’ll leave you to make your own mind up about your particular preferences.
Crepe Myrtle Fertilizer Reviews
Now on to the most important part. Following extensive research, my own experiences and knowledge, and receiving feedback from peers and other gardening experts, I present my list of picks for the 5 best fertilizers for Crepe Myrtles.
Pros
- Releases nutrients for up to 3 months
- Includes natural microbe support
- Formulated for use in the ground and containers
Cons
- Can cause foliage burn
Of course, this continuous-release formula from Miracle-Gro has everything your crepe myrtle needs to flourish. But what I love is that it also includes ingredients — kale, bone meal, earthworm castings, and more — that support the soil’s natural microbes.
The handy flip-top lid and handled container make fertilizing really simple and can be used both for ground-planted trees and shrubs and also for those grown in containers.
It’s a great product for Crepe myrtle as one dose at the beginning of the growing season will see you through for a good 3 months and no need to switch products mid-way through.
The Trial: Using these slow-release granules offered a cost-effective solution to fertilizing two rows of 4 established Crepe myrtle trees in the early spring. Even with their 6ft diameter dripline, there was still plenty of fertilizer left over for a further application the following spring.
The Results: The NPK ratio of 18-6-12 meant that the Crepe Myrtles I tested this out on got what they needed right at the start of the growing season. With 18% nitrogen, there was plenty of new growth in order for buds to soon begin to develop. Then, once bud set was underway the 12% potassium meant that flowering was plentiful throughout the summer.
One application was more than sufficient for the duration of the growing season for mature trees and I wouldn’t recommend any further applications until the following spring.
How To Use: Evenly distribute granules throughout your tree’s drip line. Water the area thoroughly. Avoid getting fertilizer on the trunk, branches, or foliage as excessive amounts of fertilizing can cause scorching or burn.
Pros
- Ideal for flowering trees and acid-loving plants
- Easy-to-use design
- Can also be broken up and applied as a powder
Cons
- Not ideal for large root systems
Miracle-Gro is a leading fertilizer brand with a reputation to match, and these spikes are specifically formulated for ornamental trees and shrubs such as your beloved crepe myrtle.
They also have an NPK ratio that is spot on for effective Crepe myrtle fertilizing: Increased nitrogen to support new growth at the start of the growing season and substantial amounts of potassium to assist with bloom development.
Whilst tree spikes are not favored by all gardeners, those with a preference for them love how they continue to release nutrients in the soil for up to 8 weeks, there is zero run-off or wastage, and they are inaccessible to pets once they have been hammered into the ground.
The Trial: The trial for these spikes involved a relatively young Crepe myrtle that was planted just 4 years ago. Established enough to not require regular fertilizing other than an application in spring, and not yet big enough to need multiple numbers of spikes.
The Results: I’m glad to feedback that my Crepe Myrtle put out plenty of new growth at a steady rate which resulted in a fabulous display of blooms over the summer months.
Thanks to the slow and steady growth rate of Crepe Myrtle, I’ll be happy to continue using these Miracle Gro spikes for the foreseeable. Not only are they beneficial to my tree, but they are also not a drain on my wallet either.
How To Use: Soak the soil thoroughly before attempting to hammer spikes into the ground. Use 1 spike per 4ft of dripline, evenly spacing the required number as you go. Do not exceed the number of spikes stated on the packaging. Hammer the spikes until completely sunk into the ground. Apply in early spring before new growth emerges. For new saplings, continue to apply every 8 weeks until Fall.
Pros
- Delivers nutrients for up to 2 months
- Can be applied by hand or with a spreader
- Safe for a variety of landscape plants
Cons
- May have a strong smell
This slow-release fertilizer from Scotts is a great choice for any ornamental tree or shrub, including crepe myrtles. Each application lasts for up to 2 months, so there’s no need to worry about constantly fertilizing your garden.
Whilst the blend of N-P-K isn’t as balanced as some other fertilizers in my top pick, this stands out as one to use at the start of the growing season before buds are formed. You can always switch up to a formula with a higher concentration of potassium as the season progresses if needed.
The Trial: This worked out well as a top dressing in springtime for a border of acid-loving plants and it’s one that I’ve used in the past with success as a fertilizer for Azaleas and Hydrangeas. I found it works best when you know that the soil pH levels are in the right range for your plants and there are no known nutrient deficiencies.
The results: In all cases, there was an increase in the size and quantity of blooms thanks to how well the nitrogen levels in this product had a positive impact on the springtime growth.
How To Use: Apply granules directly to the soil by shaking the bag or, if covering a larger area, using a drop or broadcast spreader. Scotts recommends raking the granules into the topsoil to improve absorption and prevent unwanted run-off.
Pros
- Specially formulated for crepe myrtles
- Delivers consistent nutrition for up to 4 months
- Contains five different nitrogen sources
Cons
- Time-consuming application method
Using a fertilizer formulated specifically for crepe myrtles helps take a lot of the stress out of feeding your landscape not to mention a weight off your mind.
This Nelson Plant Food formula is a favorite for many professional growers and Crepe myrtle fanatics for its flower-boosting power and diverse nutrient sources.
The only consideration for many users is its limited application for use on other trees and shrubs and also the labor of love involved with administering it.
How To Use: Rather than using a broadcast spreader, apply this granular by punching holes into the soil. Holes should be placed every 24 inches within the tree’s drip line. Evenly distribute the recommended amount of fertilizer across the holes and water thoroughly.
Pros
- Phosphorus content boosts flower production
- Water-soluble formula
- Delivers instant and slow-release nutrition
Cons
- May contribute to environmental phosphorus run-off in some regions
Don’t let the N-P-K ratio fool you — this Carl Pool fertilizer is safe to use on your crepe myrtles. In fact, it’s specially formulated for them! The extremely high percentage of phosphorus helps stimulate lots of vibrant, healthy flowers from the first signs of bud-set.
Because of the high phosphorus content, I recommend testing your soil before use. And if you live in a high-risk area for phosphorus run-off, I suggest using this fertilizer for container plantings only.
How To Use: Dissolve the fertilizer in water at a rate of 1 tablespoon per gallon. Apply the solution by watering plants as usual. You can also apply this formula using a refillable hose-end attachment.
How to Fertilize Crepe Myrtles
According to the University of Georgia, newly planted crepe myrtles should be fed at a rate of 1 teaspoon per month for the first growing season. When planting, apply fertilizer around the perimeter of the root ball before covering it with soil and watering in.
For mature crepe myrtles, apply granular fertilizer with a nitrogen ratio of 10 or less at a rate of 1 pound per 100 square feet. Fertilizers with a nitrogen ratio over 10 should be applied at a rate of .5 pounds per 100 square feet. Apply fertilizer over the drip line area, avoiding direct contact with the tree’s trunk.
Of course, the amount of fertilizer you use depends on the manufacturer’s instructions on the product you’ve bought and the size of your Crepe myrtle.
Fertilizer Burn on Crepe Myrtles
When it comes to fertilizing crepe myrtles, less is more. Over-fertilizing is one of the most common issues gardeners face when cultivating this plant.
The first sign of over-fertilization in crepe myrtles is an over-production of foliage.
This may not seem like a problem at first. But it means less energy is available for the crepe myrtle to put out its trademark blossoms.
As with any plant species, you should use a soil test kit before fertilizing crepe myrtles. A basic soil analysis will help you target nutritional deficiencies and avoid the risk of potential over-fertilizing.
Fertilizing Crepe Myrtles in Pots or Containers
All types of fertilizer can be used on potted crepe myrtles — liquid, granular, spikes, synthetic or organic. As with in-ground trees, I prefer a slow-release formula or spikes that get to work over a prolonged period of time and avoid the risk of run-off.
Container plantings naturally need more fertilizer than their in-ground counterparts.
The most important thing to remember about fertilizing potted crape myrtles is to cease feeding up to two months before the first frost date. Crepe myrtles go dormant in the winter and excess nutrients in the soil will do more harm than good.
Apply fertilizer each spring when your potted crepe myrtle first comes out of dormancy. Continue applications throughout the spring and summer per the directions of your chosen fertilizer.
When to Fertilize Crepe Myrtles
Young crepe myrtle trees should be fertilized at the time of planting and then several times throughout the first growing season — as often as once per month.
Established crepe myrtles benefit most from being fed first thing in early spring. Aim to apply fertilizer after pruning crepe myrtle but before the tree puts out new growth.
How Often to Feed Crepe Myrtles
Spring isn’t just the best time to fertilize mature crepe myrtles. It’s often the only time you should.
Some gardeners fertilize their crepe myrtles again in the fall. To prevent over-fertilization, this second feeding should only be done if a soil test shows nutritional deficiencies.
Verdict: Best Fertilizer for Crepe Myrtles
I’m a strong believer that fertilizer is a tool, not a miracle cure. So I encourage you to choose the best fertilizer for crepe myrtles based on the needs of your own landscape or garden as well as the size and health of your plants.
My number one choice for fertilizing Crepe Myrtles and getting their growing season underway successfully is to buy Miracle-Gro Shake N’ Feed Plant Food 18-6-12
Or, for smaller Crepe Myrtle or when growing in pots or containers, opt for the no-fuss, mess-free option that is Miracle-Gro Tree & Shrub Plant Food Spikes 15-5-10.
For a high-quality formula that caters to improving healthy soil pH and for caring for your Crepe myrtle’s nutritional needs all season long, I recommend Scotts Flowering Tree & Shrub Plant Food 11-7-7.
Best Slow-Release Fertilizer
Miracle-Gro Shake ‘N Feed Plant Food 18-6-12
Perfect choice for getting your Crepe Myrtle fertilizing off to a flying start at the beginning of the growing season. Can also be used as an all-purpose feed for many other trees and shrubs.
Best Fertilizer Spike
Miracle-Gro Tree & Shrub Plant Food Spikes 15-5-10
Ideal for small or potted varieties or young Crepe Myrtle to support strong and vigorous root growth and protect against disease.
Best Top Dressing
Scotts Flowering Tree & Shrub Plant Food 11-7-7
Perfect choice for helping to amend soil pH to enable season-long Crepe Myrtle fertilizing. Also suitable for use as an all-purpose feed for many other trees and shrubs.
FAQ’s Fertilizing Crepe Myrtle
Citation
University of Georgia – Prepping Crepe Myrtle for Success
