When To Fertilize Crepe Myrtles

Knowing when to fertilize crepe myrtles is the key to getting those stunning, long-lasting blooms everyone loves. If you time it right, you can encourage a spectacular summer show and a healthier tree. Get the timing wrong, and you might end up with lots of leaves and few flowers, or even harm your plant. This guide will walk you through the simple schedule and methods for feeding your crepe myrtles for optimal blooming results.

Crepe myrtles are tough, but they do benefit from a little nutritional boost, especially if your soil isn’t perfect. The goal is to support growth and flowering without causing excessive, weak growth that’s prone to pests. Let’s break down the best time to feed them and how to do it properly.

This is the golden rule: fertilize in late spring, just as the plant is coming out of dormancy and new growth is starting. For most regions, this means a single application around early to mid-May. This timing gives the plant the nutrients it needs to fuel the upcoming bloom cycle without stimulating tender new growth too early, which could be damaged by a late frost.

You should avoid fertilizing in late summer or fall. Fertilizing too late in the season encourages new growth that won’t have time to harden off before winter, making it susceptible to cold damage. Stick to the once-a-year spring schedule for established plants.

The Ideal Fertilizing Schedule

Here is a simple annual schedule to follow:

Early Spring (March-April): Test your soil if possible. This tells you exactly what your soil lacks.
Late Spring (May): Apply your chosen fertilizer. This is the main and often only feeding needed.
Early Summer (June): If your plant is in very poor soil or showing signs of deficiency, a very light second application might be okay. Usually, it’s not necessary.
Mid-Summer Onward: Stop all fertilization. Let the plant focus on flowering and preparing for dormancy.

Signs Your Crepe Myrtle Needs Food

While the spring schedule is reliable, watch for these clues that your tree could use help:

Very pale green or yellow leaves (chlorosis), especially if the veins remain green.
Stunted growth compared to previous years.
Significantly reduced flowering despite good sun exposure.
Leaves that are smaller than usual.

What About Newly Planted Crepe Myrtles?

For a tree just planted this season, hold off on fertilizing. Wait until its second spring. The first year, it’s focusing on establishing roots, and fertilizer can stress it or burn tender new roots. Just ensure it gets adequate water.

Choosing the Right Fertilizer

Not all plant food is created equal. For crepe myrtles, you want a balanced, slow-release formula.

NPK Ratio: Look for a balanced ratio like 8-8-8, 10-10-10, or 12-4-8. The first number (Nitrogen) supports leaf growth, but too much means all leaves, no blooms. A balanced formula promotes overall health.
Slow-Release: This is crucial. Slow-release granules feed the plant gradually over months, preventing a surge of weak growth and reducing the risk of burn. It’s much safer and more effective.
Specialty Blends: Fertilizers labeled for trees & shrubs or for flowering plants are also excellent choices, as they are formulated with the right nutrient balance.

A Note on Soil pH

Crepe myrtles prefer slightly acidic to neutral soil (pH 5.5 to 7.0). If your soil pH is too high (alkaline), the plant can’t absorb iron properly, leading to yellow leaves. If a soil test reveals high pH, you may need to apply a soil acidifier or a fertilizer that contains micronutrients like iron and sulfur.

How to Apply Fertilizer: A Step-by-Step Guide

Doing it correctly ensures the roots get the food without damage. Follow these steps:

Water First: A day or two before applying, water the soil around your crepe myrtle thoroughly. Fertilizing dry soil can shock the roots.
Measure: Calculate the correct amount. Read the fertilizer bag label for the recommended amount per square foot or per plant size. It’s better to use slightly less than to overdo it.
Spread Evenly: Sprinkle the granules evenly on the soil starting a few inches from the trunk and extending out to the drip line (the area directly below the outermost branches). This is where most of the feeder roots are.
Water Deeply: Immediately after applying, water the area deeply again. This helps dissolve the fertilizer and carries it down to the root zone. It also prevents the granules from sitting on the surface where they can be lost or cause burn.

The Danger of Over-Fertilizing

More is not better. Over-fertilizing is a common mistake that can seriously hurt your crepe myrtle.

Excessive Leaf Growth: You’ll get a lush, green bush with very few blooms.
Weak, Succulent Growth: This attracts pests like aphids, which secrete honeydew and lead to sooty mold.
Root Burn: High salt concentrations from fertilizer can actually damage the roots, causing leaf scorch, browning, and overall decline.
Pollution: Excess nutrients can run off into waterways, causing environmental problems.

Other Keys to Optimal Blooming

Fertilizer is just one piece of the puzzle. For the best flower show, you must also provide:

1. Maximum Sunlight

Crepe myrtles need full sun—at least 6 to 8 hours of direct, unfiltered sunlight per day. Less sun equals fewer blooms, it’s that simple. If your tree is shaded, consider pruning surrounding branches to open up the canopy.

2. Proper Pruning (And Avoiding “Murder”)

Prune in late winter while the tree is dormant. Remove crossing branches, suckers from the base, and thin the center to allow for air flow. Avoid “crepe murder”—the harsh practice of chopping all branches back to stubs. This ruins the tree’s natural shape and causes weak, knuckled growth that supports fewer blooms. Light, selective pruning is the way to go.

3. Adequate Watering

While drought-tolerant once established, crepe myrtles need consistent moisture during the growing season, especially during dry spells and just before and during flowering. Deep, infrequent watering is better than frequent sprinkles. A good rule is to water when the top 2-3 inches of soil feel dry.

Frequently Asked Questions (FAQ)

Can I use Miracle-Gro on crepe myrtles?

Yes, a balanced, all-purpose Miracle-Gro (like their Shake ‘n Feed for Trees & Shrubs) is a suitable option. Just ensure you follow the label directions and opt for a slow-release formula if possible.

Is Epsom salt good for crepe myrtles?

Epsom salt provides magnesium and sulfur. Only use it if a soil test confirms a magnesium deficiency, which can cause leaf curling. Unnecessary use can disrupt soil nutrient balance. It is not a substitute for a complete fertilizer.

What is the best month to fertilize crepe myrtle?

May is generally the best and safest month for most climates. It’s late enough to avoid frost damage on new growth but early enough to support flower formation for the summer.

Why is my crepe myrtle not blooming even with fertilizer?

If you’re fertilizing correctly, look at other factors: Not enough sun is the top cause. Improper pruning (or “murder”) is the second. Also, some varieties simply bloom later in the summer. Check that you’re not using a high-nitrogen lawn fertilizer nearby, which can seep into the roots and promote leaves over flowers.

Should you fertilize crepe myrtles in the fall?

No, you should not fertilize crepe myrtles in fall. This can stimulate new growth that will be killed by winter cold, wasting the tree’s energy and making it more vulnerable.

By following this simple calendar—fertilizing once in late spring with a balanced, slow-release product—you give your crepe myrtle exactly what it needs. Combine that with full sun, proper pruning, and good watering, and you’ll be rewarded with a summer full of vibrant, beautiful blooms that last for months. Remember, patience and consistency are key to a healthy, flowering tree.