How to Plant, Grow, and Care for Creeping Phlox

In shades of white, pink, red, purple and blue, phlox is an incredibly popular, brilliantly-flowered ornamental. Whether it’s creeping phlox spreading out to become a beautiful ground cover, or a mounding phlox in the garden, these delicate flowers are definitely a sight to behold.

The term “phlox” originates with the Greek word for “flame”, likely referencing some of the red shades. However, most phloxes growing wild throughout North America tend towards lighter hues.

Let’s explore some of the diversity of phlox species today, as well as go over the best way to ensure you have a proliferation of bright blooms throughout the year!

What is Creeping Phlox?

Phlox encompasses several species of annuals and perennials. Some are upright, and others are more low-lying. All can be an excellent ground cover, as they readily self-seed and easily spread on their own.

Native Area

Phlox species are mostly relegated to the prairies and woodlands of North America, but there are some varieties that cover the northern parts of Asia. They thrive in diverse habitats, ranging from alpine tundra to open woodlands and prairies. Most species can be found in temperate regions, with many varieties adapted to specific climates and soil conditions. Phlox is often found in sunny locations with well-drained soil, making it a favorite in wildflower gardens.

Characteristics

The stalks of all phlox plants are green when they’re young, and grow woody as they mature. Flowers bloom at variable times, and in different shades from white, to pink, to violet. Many are native plants that host important butterfly and moth pollinators.

Phlox plants are perfect for planting on slopes and in rock gardens. They survive in poor soils and cover ground for erosion control. During their blooming period, they’ll provide pops of color. Though they may die back in cold winters, they’ll return again in spring via their spreading and branching roots.

Varieties

There are 67 species in the Polemoniaceae family, all of which are considered to be phlox. While I can’t cover them all in one go, let’s review a few of the more popular varieties.

Phlox subulata

With petals that tend towards heart-shaped or which have tiny teeth at the edges, creeping phlox is a very popular perennial. It is also commonly known as moss phlox, mountain phlox, or moss pink. Native to the eastern and central portions of the United States, Phlox subulata has needle-like leaves on slender stems. Its coloration can range from rose and mauve to lavenders, blues, and whites as well.

One of the cultivars of this species, the rose-pink variety known as ‘McDaniel’s Cushion’, has won an Award of Garden Merit from the Royal Horticultural Society.

Phlox paniculata

Clumps of flowers in tones of pink, red, purple, or white are a sign of Phlox paniculata, also known as garden phlox, tall garden phlox, perennial phlox, and summer phlox. Named after its pannicles (clustered blossoms), this plant is often grown as a small shrub or trained to a bushing habit. It originates in the eastern and central United States and can be found in eastern Canada as well.

Twelve separate cultivars of Phlox paniculata have gained the Award of Garden Merit. Tall phlox or garden phlox is incredibly widely grown as an ornamental plant and is popular worldwide.

Phlox drummondii

A native to Texas, Phlox drummondii is also widely spread across the southeastern United States. It is named after the Scottish botanist Thomas Drummond. Common names include Drummond’s phlox and annual phlox. This phlox ranges from creamy colors all the way through a purple so dark that it’s nearly black.

This particular species is often seen planted along highways throughout the southeastern United States, but is widely found in gardens as well. A popular variation is the variegated ‘Twinkle Star’ variety, which ranges from pale pink to hot pink in color.

Phlox carolina

With a pair of cultivars that have also gained the Award of Garden Merit from the RHS (the ‘Bill Baker’ and ‘Miss Lingard’ cultivars specifically), Phlox carolina is a common sight in the eastern US. Originating in the Carolinas, from which it takes its name, this species tends towards purple, pink, or white blossoms.

The common name thickleaf phlox is apt, given that this has a very wide leaf pattern in comparison to other phlox species. The greenery tends towards darker tones, making the flowers stand out brightly against the leaves and stems.

Phlox divaricata

The woodland phlox, Phlox divaricata, can be found in forests and fields along the eastern portion of the United States. There are two subspecies of this species. Subspecies divaricata has notched ends to the petals, where subspecies laphamii does not. They also go by the names wild blue phlox and wild sweet William

The ‘Chattahoochee’ cultivar of Phlox divaricata spp. laphamii has won an Award of Garden Merit from the RHS for its lavender blossoms with brilliant purple-pink centers. Other popular cultivars include ‘Blue Moon’, ‘Fuller’s White’, and ‘Clouds of Perfume’.

Phlox condensata

Phlox condensata calls the western United States home, especially the mountainous portions of eastern California, Colorado, and Nevada. As a ground cover, this perennial dwarf phlox is nearly ideal, since it rarely grows to any significant height and has a tendency to form a creeping phlox mat along the ground’s surface. It seems to prefer rockier, well-draining soils.

The pure white flowers of this phlox plant are slightly violet in the center of their petals. Within the pure white flowers are a bright yellow center as well.

Phlox diffusa

This perennial form of spreading or creeping phlox is distributed throughout the western United States and into British Columbia. Often, it forms patches of flowers across hills and mountain slopes. Slightly taller than the dwarf phlox, Phlox diffusa is more commonly found in the wild than in garden settings, although it can be easily transplanted to gardens as well.

Phlox stolonifera

Not to be confused with Phlox subulata, Phlox stolonifera is indigenous to the Appalachian mountains and surrounding woodland areas. It can be found as far north as Quebec, Canada, but is primarily located in the United States.

Phlox stolonifera gets its name from its stolons or runners, which make it a creeping phlox variety, sometimes called moss phlox. This variety is most commonly found in the wild and is pink, purple, or white in petal color. Its oval leaves and six to ten inches height, make it a particularly pretty ground cover.

Phlox adsurgens

Native to Oregon and parts of the coastal California mountains, Phlox adsurgens tends towards five-petaled pink flowers with cream or white markings. Some petal shapes tend to point at the tips, making them look like tiny pink stars, while others remain rounded at the tip, like those seen above.

These are most common in forested or woodland areas. While they are slowly gaining popularity as an ornamental variety for garden use due to the beauty of their coloration, they’re still most common in their natural environment. In the nursery, they could be called woodland phlox or northern phlox.

Planting

Start the planting by Choosing a location with well-drained soil and plenty of sunlight, as most phlox varieties thrive in full sun, though some woodland types prefer partial shade. Enrich the soil with compost or organic matter to improve fertility and drainage. Space the plants 12 to 18 inches apart, depending on the variety, to allow for good airflow, which helps prevent diseases.

Dig a hole slightly larger than the root ball, place the phlox at the same depth it was growing in its pot, and backfill it with soil. Water thoroughly after planting and apply a layer of mulch to retain moisture and suppress weeds. Read on about how to grow.

How to Grow

Phlox is surprisingly low-maintenance, but there are a few things you can do to guarantee the best results.

Light

Most of the creeping phlox varieties like full to partial sun. These include both the border species like Phlox carolina and most of the woodland species. Any of the mounding varieties, such as Phlox paniculata, prefer full sun. As long as your phlox plant gets a minimum of six hours of light per day, you should have good growth potential.

Water

In general, most phlox prefer a minimum of one inch of water per week. However, areas that get hot may require more water. It’s important to always water phlox, whether creeping phlox or the mounding varieties, down at the base. In fact, it’s easiest to simply use drip irrigation around phlox, as it will reduce the risk of powdery mildew or other diseases.

A good rule of thumb for the phlox is that if you can feel moisture in the soil when you stick your finger a couple inches beneath the soil’s surface, you should be alright. Adding mulch to retain soil moisture is advisable. Humidity tolerance for phlox is wide.

Soil

Rich soils are optimal for phlox. The soil for your creeping phlox should be on the alkaline side of neutral (6.5-7.0), so if your soil is acidic, a bit of horticultural lime would be a good addition. They prefer lots of organic matter in the soil, so amend your soil with aged manure or compost.

Good drainage is required, as these perennials don’t like to have wet feet. However, they do not do well in hot, dry soil, so be sure that the soil remains evenly moist. Two inches of mulch around the base will also help to keep the moisture level.

Temperature

Heat is no problem for phlox, and temperatures down to 40°F (4°C) are usually suitable, too. However, some varieties and species are not tolerant to frost and will die back in prolonged freezing temperatures. Most will return in spring.

Fertilizing

If you add an inch or two of compost around your perennial phlox once per year, chances are that you won’t have to fertilize them. However, if you do fertilize them, be cautious. Too much nitrogen can cause phlox to produce lots of leaves and fat stem growth instead of the pretty white, purple, blue, pink, and red phlox flowers that we want to see!

Fertilizer choices for your phlox should be slow-release granular options, preferably ones that release nutrients over a four- to five-month period of time. Broadcasting a balanced granular option around your phlox as they’re putting up new spring growth is perfect.

Some of the taller varieties of phlox, such as Phlox paniculata (known as tall phlox or garden phlox), also appreciate a secondary side-dressing of a liquid fertilizer during the summer months to keep producing color during the hotter months. However, the best bet is to ensure your soil is rich and fertile before planting and add compost or leaf mold annually, and they will take it from there.

It’s also important to be mindful of what else is around the area. Planting creeping phlox underneath trees or large shrubs or bushes is a bad idea, as it puts your phlox in immediate competition for soil nutrients. If you do decide to grow near larger shrubs or trees, you may need added fertilizer to keep your phlox healthy. That way, you can enjoy pink, purple, blue, or pure white flowers.

Maintenance

Taller varieties of phlox, like Phlox paniculata (aka tall phlox), will benefit from thinning early in the year. Once it has reached a six to eight-inch height, leave at least a half-dozen strong stems and trim the others back to the base. Once you’ve finished thinning the stems, pinch off the top of each remaining stem just above a leaf bud to encourage bushier growth.

Deadheading the spent phlox flowers is essential to prevent accidental reseeding. Regularly removing the spent flowers also encourages them to bloom more, keeping the color going for a longer period of time.

Trim back shorter, creeping phlox varieties like Phlox subulata and Phlox stolonifera once they’ve finished flowering. Trim a third to half of their height once flowering has subsided. This encourages a denser matting pattern and more flowers in the next blooming season.

If you’ve just divided your phlox, it’s important to be sure you have rich soil ready to grow in. Divided should be examined, and any damaged or unhealthy roots should be trimmed. Make a hole in your planting location or pot, and then gently spread out the roots so they have plenty of room before covering them with fresh soil.

If you’re simply repotting into a larger pot or bed to allow it to continue growing, carefully dig it out of its prior container or bed. Examine the roots and trim off any unhealthy ones, and then plant it as if it were a divided bit, being sure there’s plenty of room available for expansion.

Propagation

While you can propagate most varieties from seed, phlox is easiest to propagate from cuttings. A six- to eight-inch cutting will take root extremely easily in water, potting mix, or perlite.

If you have a particular cultivar that you’re trying to maintain, cuttings are definitely the best way to go, as seed will not always produce true copies of the parent. In fact, it’s important to deadhead the fading flowers before they can release seed because phlox will readily self-seed, and the resulting seedlings might not be what you expect!

Some varieties, such as Phlox stolonifera, also will propagate from runners or stolons beneath the soil’s surface. These types can spread quite rapidly. Keep an eye on these beds and be ready to trim back runners that are trying to travel out of their planned space.

You can also propagate phlox from division. Every few years, carefully remove in the early spring and cut them into smaller chunks with a sharp, sterile knife or shears. Replant part of it, and then either expand your phlox bed or place the other segments into pots to give away to friends or family. This also gives you the ability to amend your soil at the same time, working more compost or aged manure into it to ensure it’s nutrient-dense.

Common Problems

If you’ve done all of the stuff I mentioned above, it’s likely that your phlox is thriving. But what if it isn’t? Here’s a few things that you might not have considered.

Growing Problems

Often, people who plant a creeping phlox ground cover have high hopes of a carpet of pretty pink or purple phlox flowers. However, Phlox subulata requires full sun conditions for best performance, so shadier environments can make for weedier, less-full growth, and a distinct lack of floral display. If you are trying to encourage a phlox ground cover, be sure that you have good sun coverage. If most of your location is partial shade, consider Phlox stolonifera, which does better in partial shade conditions than subulata does.

Browning in the center of a creeping phlox is usually an indicator that your roots are becoming crowded. If the center of the phlox is starting to die back, carefully dig up, divide it into multiple smaller sections, and replant it to allow for more root growth.

Wilting phlox is most commonly caused by improper watering techniques. If the soil is dry for too long, phlox have a hard time when an influx of water happens, as they can’t easily take up the soil nutrients or water to replenish themselves. Keeping the soil evenly moist will prevent this problem. Be careful not to overwater, as that can damage roots and actually cause it to start to drown and wilt from too much water!

Pests

Spider mites are a common pest on both creeping phlox varieties and mounding tall phlox varieties. To prevent spider mites on phlox, a thorough spraying of neem oil on all plant surfaces will take them out. This also works well against aphids, which are another very common pest on phlox.

The phlox plant bug,  Lopidea davisi, is a highly-specialized pest. Feeding primarily on the sap of phlox, it can cause spotting and stippling on leaves, later developing into browning and death. It’s advised to prevent the bug’s appearance by using insecticidal soap and cleaning up plant litter or dead stems.

Snails and slugs may also take shelter in and around your phlox. While these cause minimal damage to the phlox itself other than a few nibbled leaves, they can cause damage to other perennials in your garden. Use slug and snail traps around and through your phlox patch to deter these common pests.

Diseases

One of the most common diseases to hit phlox is powdery mildew. This is especially true in areas that have hot, humid summer conditions. You can control this by applying neem oil to all plant surfaces. Planting mildew-resistant cultivars is also an option, as there are a number of them available now.

Fungal leaf spot can also be a problem. Thankfully, this, too, can be treated by regular applications of neem oil. If you are seeing signs of leaf spot, apply once a week until the spotting subsides. Then apply monthly to prevent another outbreak.

Some phlox are susceptible to rust, and perennials like phlox are susceptible to crown, stem, or root rot issues. These generally develop because of bacteria in the soil that develop when the soil is overly wet. To prevent these, ensure your soil is moist, but well-draining, and that any plant debris is cleaned away from your plants. Plants which develop rot issues should be removed and destroyed to prevent any further spread of the bacteria.

Frequently Asked Questions