How to Grow Garden Phlox for a Late Summer Bloom
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 much like 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.
Plox 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 a hardy perennial plant 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.
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 more bushy. 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 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.