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How to Grow Garden Phlox for a Late Summer Bloom

Phlox Paniculata or Garden Phlox.

Phlox Paniculata or Garden Phlox.

Phlox have been a favorite flower of many, including myself, for years. The Paniculata phlox, also known as Tall Phlox or Garden Phlox, can be seen growing in the yards of many old, abandoned houses or spread along roadsides.

Paniculata phlox grows tall, sometimes as high as five feet. Other than its growth habit, it is similar to the creeping phlox as the flowers look much the same.

I have five different varieties in my own garden because they make such a big show when they bloom. This is one flower you should include in any perennial bed.


Phlox is a perennial that will return year after year. It is available in many pretty colors, including lavender, orange, various shades of purple, pink, red, white, and salmon. You can find phlox that are bi-colored, as well as some with eyes. A new variety called Candy Twist is even striped.

The plants bloom in July and August. Newer ones are advertised to bloom in September. Be sure to check that the variety you purchase is mildew resistant since this is a disease that is common to phlox.

Before purchasing your plants, check the tags for hardiness zones. Most phlox are hardy perennial plants in Zones 4–8. Look at the tag on the plant before purchasing, because some varieties are available for hardiness to Zone 2 and some will withstand the heat in Zone 9.

The plant can reach 2–5 feet depending on the variety. Many are fragrant and attract lots of hummingbirds and butterflies.

Garden Phlox.

Garden Phlox.


The plants will grow in 24" to 36” mounds, so keep this in mind when planting. Strong winds will often blow the plants down and cause some damage. You may want to plant it near a fence or somewhere where it will get some support. Caging them is also a good idea. I cut mine down in the spring, so they don't grow so tall and are bushier. This has worked for me without caging.

Look for a spot that gets at least 4–6 hours of sunlight a day. Phlox love the sun, but they will grow in partial shade. You want to plant them in rich ground. If the ground isn't rich, be sure to add some composted cow manure.


It is a good idea to thin the branches every spring. Cutting some of the top growth down in the early spring will help it be a stronger plant. Do this several months before the blossom buds start forming.

These plants like lots of water, but don't water from the top. This would encourage disease. Instead, water from the bottom.

The plants should be cut down in the fall.

Diseases and Pests

The main disease you'll have problems with is powdery mildew. This can be prevented by spraying with sulfur every couple of weeks.

Your plants may also develop root rot. If you purchase varieties resistant to powdery mildew and see that the plant gets plenty of air, you won't have to deal with that either.

Insects that may bother your plants are spider mites, stem nematodes, leaf miners, and caterpillars. You may not have these problems either unless you are already having the same problem with your other perennials.


Divide the plants in the spring and fall. These plants are easy to propagate from cuttings. Since you should thin the branches in the spring, this will give you lots of starts. To be sure that all branches start, use a rooting hormone. Phlox can also be started from seeds.

Phlox are so easy to propagate that one year I tried to start all of the cuttings after trimming in the spring. I figured they wouldn't all start. I ended up with enough to share with friends and made some good pocket money selling them at my garage sale. So take it easy when propagating.

Hummingbird moth collecting nectar from Phlox flowerbed.

Hummingbird moth collecting nectar from Phlox flowerbed.

© 2013 Barbara Badder


Barbara Badder (author) from USA on August 17, 2017:

You can cut them down to 5". This would only be to make things look tidier. Phlox are quite tough and aren't even easy to get rid of, so I'd say either way would work.

So what do I do to them in fall? Should I cut them down low or just let them die off and separate them in the spring? Thanks on August 15, 2017:

So should I cut them short in the fall or wait till doing? Thanks

Barbara Badder (author) from USA on May 15, 2013:

Marsha, I think I've seen the ones you are talking about at old homesteads. They are spread across almost the entire yards. My husband doesn't care for their smell. I wish the ones I have would spread a little bit. Thanks for commenting.

Marsha Musselman from Michigan, USA on May 14, 2013:

The phlox you have highlighted in your hub are beautiful. I especially like the looks of the variegated one. The flower of that one reminds me of dianthus even though the leaves are obviously different.

I have a variety of phlox in my flower bed that I would prefer to get rid of as it's very invasive. I have a friend that has the type you have here that grows in contained areas, whereas, the ones I have take over—almost like an invasive ground cover. Mine are white and I've been allergic to them in the past.

Great, informative article.

Barbara Badder (author) from USA on March 26, 2013:

sgbrown, Thanks for reading and yes I'd love it if you shared it on your blog. If your plant was small when you purchased it, you may not want to prune it the first year. Once they get large, they have so many branches that you will want to do it. Thanks for your comments.

Sheila Brown from Southern Oklahoma on March 26, 2013:

I planted some purple phlox last year and was very happy with it. I can't wait for it to come back this year. If it comes back well, I will surely buy some more. I appreciate the tips on how to care for phlox and I will definitely try some cuttings from it too. Voted up, useful, interesting,pinning and I would like to share this on my blog, "Sheila's Flower Garden Get A Way" at blogspot, it that is ok with you. Great hub! :)

Barbara Badder (author) from USA on March 23, 2013:

pstrabie48, I'm happy I gave you some good memories. Yes, you'll need to plant some and then you can have those good memories every time you see them blooming.

Patricia Scott from North Central Florida on March 23, 2013:

Barbara Kay

Thanks for sharing this with us. Phlox bring back a whole rush of memories. My Momma used to have a whole yard full of these when I was growing up. I will just have to get some for my yard now that you have explained the essentials.

Sending Angels your way :) ps

Susan Holland from Southwest Missouri on March 23, 2013:

My grandmother used to plant phlox. I love them. Thank you for this informational guide to growing phlox! :-)

Votes and shares!

Barbara Badder (author) from USA on March 22, 2013:

faythef, I looked this up for you and it does say that some varieties to have a sticky substance. I guess you will need to find one that doesn't.

Barbara Badder (author) from USA on March 22, 2013:

faythef, I've never heard of phlox getting a sticky substance. It sounds like an insect problem. I'd give it a try. Thanks for reading.

Faythe Payne from USA on March 22, 2013:

I love phlox..I had one huge plant that I took out because it kept getting a sticky residue on it..I had no idea that I could have just cut it back...Maybe I should try again