8 Reasons Why Is My Phlox Not Flowering? [Treatment]

Summer and blooms in your phlox plants are the best combinations ever! With the fragmented beautiful small flowers, these herbaceous plants are absolute show stealers in your garden. Even though there is a wider range of varieties of phlox plants, all of them grow with pretty bush and blooms.

The plants are also easy to grow. With sturdy stems, they are hardy and low-maintenance as well. Yet, some phlox growers are often found wondering, why their phlox are not flowering!

Well, different variety phlox bloom at different times. Creeping phlox is found to bloom in early summer or late spring whereas the tall phlox plants bloom between mid and late summer.

So, if your healthy-looking phloxes are still not blooming even when it is high time, there must be some reasons. Phlox may not flower because of the wrong environment, improper planting, insufficient nutrients, or other reasons.

Let’s dive into each reason that is affecting the efficiency of your phlox to produce the flower.

Why Your Phlox is Not Flowering [Reason & Control Measure]

full of flower Phlox tree

1. Insufficient Sunlight

Any plant will deteriorate and won’t flower or give fruit if it is planted in the wrong environment. Phlox plants are also not an exception. For growing proper bushes and producing blooms, these plants require the right environment where they can get sufficient sunlight.

Phlox plants require direct sunshine of about six hours or more. So, you have to ensure sunlight while planting phlox.

Control Measure

  • Plant your phlox plants in partial shade or sunny spots.
  • If you have already planted your phlox then dig and move them to a sunnier place.

2. Susceptibility to Powdery Mildew

Phlox plants are highly susceptible to powdery mildew. Gardeners who have grown this plant before will know it better. Powdery mildew is the result of fungal infection. It gradually weakens the whole phlox plant and affects the capability of blooming.

This disease is very common to phlox. If your plant is suffering from this disease, you will hardly see it producing flowers. Powdery mildew mostly attacks when overhead watering is caused.

Moreover, hot and humid weather is favorable for powdery mildew. The damp environment helps in increasing their spore germination. It happens when your phloxes are planted in a partial shade location.

The spores of powdery mildew fungus are the greatest survivors. They can overwinter within the tissues of debris plants for years. They can survive in cracks in crevices as well.

Control Measure

  • Do not allow overhead watering to your phlox plants.
  • Ensure a dry environment and soil to stop the spore germination of powdery mildew.
  • Remove old debris and dead plant materials from the garden before planting new phlox plants.
  • Remove the affected foliage and destroy them.
  • Clean the fallen leaves and burn them.
  • Do not let the foliage wet while watering.
  • Increase air circulation of the plants by thinning them out in early spring.
  • Also, keep clean the environment where your phlox is growing.
  • You can go for homemade recipes as well,

#Spray Vegetable Oil

Required Materials:

  • Vegetable oil
  • Baking soda
  • Dish soap
  • Water


  1. Mix one tablespoon of vegetable oil with one tablespoon of baking soda.
  2. Add one teaspoon of dish soap and mix with one gallon of water.
  3. Take the mixture in a spray bottle and then spray over powdery mildew.

However, if the plant shows a severe attack of powdery mildew, then you can use a commercial fungicide (our pick: Bonide 811 Copper 4E Fungicide).

3. Competition For Nutrients

Many gardeners out there do the mistake of planting phlox around trees or other plants that later compete for nutrients.

Phlox requires sufficient nutrients to grow and finally flower. But if it has to compete for nutrients and water, it might not get enough essential nutrients to flower. So, eventually, flower production gets affected as well.

Control Measure

  • Try to plant your phlox plants in an area where there will be no other plants for nutrient competition.
  • Do not allow any generation of weed near your phlox plant.

4. Pruning in the Wrong Method

Pruning Tall Summer Phlox

To speak fact, pruning your phlox plant induces the growth of bush along with flowers. Trimming off the bushes keeps your phlox plant in shape always. It also ensures sufficient airflow.  

Pruning also helps in reducing the powdery mildew of the phlox plant. But pruning off following the wrong method brings exactly the opposite result.

Again, selecting the wrong time for pruning will also result in no flowers. The flowering season of phlox is summer or spring. Pruning at this time of year will certainly not going to help with flowering.

In fact, it would be counterproductive. Moreover, many unskilled gardeners prune off the flower buds instead of dead leaves and wood.

Then again, your bushy phlox require some unique technique for its proper pruning. Are you sure, you are following them properly? Improper pruning delays flowers.

Control Measure

  • Do not prune in between early and mid-summer.
  • Prune only the dead wood and not the living wood.
  • Do not prune buds that will bloom in summer.
  • You should prune the phlox depending on the variety.

So, first, know the variety of your phlox. Pruning after the blooming season is the best idea. Also, to have your phlox flower stay a little longer, deadhead them. Deadheading at the right time increases flower production.

5. Phlox in Drought

Phlox plants are unlikely to survive in drought conditions. Dry weather makes the foliage wilted in the phlox plant. Consequently, flower production also gets deteriorated.

So, it is predictable that phlox requires sufficient moisture in the soil. Therefore, their metabolism for flowering does not function well in drought conditions.

Control Measure

  • Water your phlox in the morning regularly when the weather is hot.
  • Make sure, the roots of the phlox get enough water to function the growth of both bush and flower.

However, to determine if the foliage of the phlox plants is hydrated or dehydrated, you can use a moisture meter (Our pick: SONKIR Soil pH Meter, MS02 3-in-1 Soil Moisture/Light/pH Tester). Detecting the level of moisture, you can water your plants accordingly.

6. Unsuitable Zone and Soil

Like any other plant, phlox also requires a specific hardiness zone for its proper thrive and grow. Its compatible USDA hardiness zone lies between 4 to 9.

Again, to talk about suitable soil, phlox grows well in well-drained sandy soil with sufficient nutrients. If the soil is previously treated with enough organic compost, it will thrive beautifully offering a cluster of flowers.

Control Measure

  • Before planting the phlox plant, get the soil tested where you intended the plant. And then take steps accordingly.
  • Tilt the soil properly as well before planting the phlox.
  • Mulch the soil around your phlox plant to improve drainage and water retention. A thick layer might work better.
  • If the soil has drainage problems, consider adding some vermiculite or also perlite to the soil.
  • Add organic matter, compost, or manure to the soil to increase nutrient content.

Organic matter helps in the betterment of soil quality and texture. These materials also ensure sufficient aeration both for roots and foliage.

7. Excessive Fertilizing

Fertilizing is necessary in order to get better growth and flowers in your phlox plant just like any other shrubs. Actually, the phlox plant hardly requires fertilizer. If the soil has enough nutrients and it is sandy soil then fertilizing is not essential.

But many gardeners think the more you fertilize the more you get blooms. Whereas, it actually works in a detrimental way. Initially, gardeners fall for their desire to make their phlox plant bushy.

So, they apply an immense amount of nitrogen-based fertilizer for better foliage. But excessive nitrogen does not allow for blooming properly. For flowering well, the phlox plant requires phosphorus fertilizer.

Control Measure

  • Use a balanced fertilizer for phlox [our pick: Espoma Organic Plant-tone]
  • When buds begin to form use the best granular slow-release fertilizer.
  • Never skip the instruction part before applying fertilizer.
  • It is always better to use organic compost instead of chemical fertilizer.

If some flowers of your phlox plant start to fade, then fertilizing the soil might help in reblooming. So, you have to know what your phlox plant wants.

8. Letting Your Phlox Overgrow

Phlox plants are meant to overgrow. With an immensely bushy shape, the plant spreads and grows excessively. Excessive growth of bush is also a reason for phlox not in bloom.

The overgrowth offers only foliage and less or no flowers. And this is certainly not desirable. Overgrowing foliage sucks up all the metabolic energy. Hence, the plant lacks energy while flowering.

Moreover, overgrowing not only stops flowering in phlox but also harms its health. The plant loses its focus on the proper distribution of energy to both foliage and flower.

Control Measure

  • Do not allow the phlox plant to overgrow.
  • Divide the plant periodically when the time comes to ensure healthy survival.
  • Ensure proper distribution of energy to grow foliage and flower in proper ratio.


How do I get my phlox to bloom?

Phlox can tolerate light drought. But for severe drought, they are unlikely to survive let alone bloom. So, to get your phlox to bloom you must keep them well-watered when the weather is dry and hot.

 Also, make sure you prune and deadhead your phlox plant at the right time following the proper method.

What does phlox look like when it is not blooming?

Phlox that is not blooming does not show many differences. For say, you have creeping phlox plants that bloom in pink, purple, white, and other shades of these colors. If they do not bloom, still the plant looks healthy with needle-like green and bright foliage.

How do you keep phlox blooming all summer?

Most varieties of phlox are perennials. There are ways to keep your phlox blooming all summer. The seedlings of phlox do not bloom as they are a bit weedy. However, deadheading appropriately keeps the parent plant all work up with blooming throughout the whole summer.

How long does it take phlox to bloom?

Depending on the variety, phlox can bloom from April to June. Among all varieties, creeping phlox flowers three to four weeks heavily.

Final Word

Now that you know why your phlox is not flowering, you should work accordingly. Yes, there are certainly many reasons that are stopping your phlox and so it is not in bloom. But you have to overcome these problems by following the control measures we have shared above.

However, it is always better to know what are the environmental requirements of a plant before planting them. It makes the growing journey easier for both you and the plant.

So, if this article has helped you even a bit with your phlox growing then let us know by shooting feedback.

James Rivenburg
James Rivenburg
James Rivenburg

James Rivenburg is the founder of plantandpest.com, a passionate gardener with valuable experience and knowledge gained through trial and error. The website has a large community of followers who trust his tips and techniques and have succeeded with his advice. He is always Committed to helping others create a beautiful and healthy garden.

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