There are a lot of great groundcovers out of three, but the many phlox species are some of the most surprising for those who aren’t expecting their showy displays.
One prominent example is Phlox subulata (Floks Sub-yoo-LAH-tuh), a creeping perennial that’s native to the eastern and central US.
This proud member of the Polemoniaceae family is actually referred to as moss phlox but has been compared to its sister plant, Phlox stolonifera, so often that it shares the other plant’s common name of creeping phlox.
It’s also sometimes referred to as moss pinks or mountain phlox.
Creeping Phlox Care
Size and Growth
This creeping phlox plant doesn’t grow very tall, generally reaching 3” to 8” inches tall.
However, it can spread as far as 24” inches wide and can slowly take over the terrain if neglected.
The compact stems start off green but turn brown and woody with age.
Meanwhile, its green leaves are a key difference between Phlox subulata and Phlox stolonifera, with the former having needle-like leaves and the latter having more oval leaves.
Flowering and Fragrance
Another difference becomes apparent in April and May when creeping phlox bursts into bloom. It continues to bloom through late spring to early summer.
Unlike Phlox stolonifera, the flowers bloom almost flush with the vibrant green foliage, creating a carpet of blue, pink, purple, and white flowers.
The small, star-shaped fragrant flowers are only around ¾” inches across, but there are quite a few of them to enjoy.
While the blooms grow on both new and older growth, the chances of Phlox flowers on a stem become smaller as it ages.
Light and Temperature
This species thrives in bright, direct sunlight or full sun to be at its best, unlike its sister, which can tolerate partial shade.
In especially hot summers, a little dappled light in the afternoon can be helpful, as long as it has full sun in the morning or evening.
It’s tolerant of lower humidity levels, but too much humidity can lead to health issues.
While it’s possible to grow creeping phlox in a container, most people in USDA hardiness zones 3 to 9 prefer to grow it outdoors.
Flowering is usually triggered at 60° degrees Fahrenheit, and the plant can withstand some heat and short periods of frost.
However, it can become damaged if exposed to temperatures under 40° degrees Fahrenheit for extended periods of time.
Watering and Feeding
Creeping phlox requires consistently moist soil when young. However, it becomes drought tolerant when established.
You need to water when the soil is dry, approximately 1” inch down.
You can test this by sticking your finger directly down into the soil, with the distance from your fingertip to the first knuckle being approximately 1” inch.
Younger plants will need to be watered more frequently, but an established plant will tolerate a missed watering here or there.
Moreover, provide supplemental water only during prolonged periods of dry weather.
Avoid overwatering, as the root ball of creeping phlox hates soggy soil, and most of its potential health issues can be avoided with proper watering.
If you live in an area that gets approximately 1” inch of rain per week, you might not need to manually water your moss phlox except for during particularly hot spells.
When growing annual phlox outdoors, you generally won’t need fertilizer.
Some growers like to give it a balanced slow-release fertilizer in late winter to early spring, although adding a little organic compost is more common during this time.
You can also feed your creeping phlox with organic plant food or slow-release flower fertilizer for strong and vigorous growth.
While not necessary, this can add a little boost to the blooms. Growing your moss pinks in a container is a little different, however.
In this case, you will want to give it a balanced, water-soluble fertilizer diluted to ½ strength every two weeks.
Be sure to cut back on fertilizing as the growing season comes to a close.
Soil and Transplanting
You can grow creeping phlox in a wide range of well-drained soils.
The plant often creeps over rocks and other natural obstacles, so it has a more shallow root system than many other perennial plants.
Ideally, you will want to give it loamy or sandy soil with a pH between 6.0 and 7.0. It prefers slightly acidic soil, although it can tolerate slightly alkaline soils in a pinch.
If growing in clay soil, amend with vermiculite, coarse sand, or some other aggregate to keep the soil loose and well-draining.
You may also want to add some organic matter like compost, leaf mold, or peat moss if the soil quality is poor.
It also helps to rake the soil surface when planting any phlox plants to ensure the roots can expand easily.
Moreover, ensure to check the soil moisture after planting. This plant should be divided or repotted every 2 to 3 years.
During this time, you can divide the plant to get more or remove the oldest sections and keep the plant young and healthy.
This is also the best time to change the soil if you’re using a container.
Grooming and Maintenance
This woodland phlox doesn’t require much maintenance, but the extra attention can have a big effect.
After it flowers, you can cut it back by ⅓ to 1/2.
Not only does this encourage fuller growth and help maintain a desired shape or size, but it can also often spark a smaller second blooming period.
Some growers like to give it an additional trim or two later on the dead growth in the growing season to continue encouraging growth.
You can also prune this plant in the late summer or early fall to avoid reseeding and encourage healthy growth.
Cutting back the plant during the late winter will also enhance its new growth habit.
If you live in Zone 4 or a colder region, add a layer of mulch by the root zone to protect the phlox roots. Make sure to do this before the ground freezes.
How To Propagate Moss Phlox
The most common way of propagating moss pinks is through division every 2 to 3 years.
However, those who are more patient or adventurous can also grow new plants via stem cuttings or seeds.
Mountain Phlox Pests Or Diseases
While young, creeping phlox can be sensitive to drought conditions.
However, once it becomes established, it becomes mildly drought tolerant and has a tolerance for deer and air pollution.
Spider mites can be a problem in arid climates. You can treat your infected plant with insecticidal soap to help this problem.
More importantly, overwatering can lead to root rot and foliar nematodes.
While more resistant than other phloxes, powdery mildew can also become a problem for this plant if it’s infested with honeydew-producing pests or in overly wet conditions, or under wet, humid weather.
One piece of really good news is that creeping phlox is completely non-toxic and safe around both humans and pets.
Phlox Subulata Uses
The Mahuna traditionally use creeping phlox as a treatment for rheumatism, although there are no studies into its efficacy.
The entire plant can also be brewed to make tea to soothe gastrointestinal issues and make a person calm.
Moreover, one of the greatest advantages of garden phlox is its shallow root system.
This makes it an excellent perennial ground cover for banks and other sloped landscaping, as the roots help prevent soil erosion.
Planting on a sloped surface also creates a wonderful display when in bloom, and it’s common to see mountain phlox planted so it overhangs rock walls dramatically.
The plant is also a great addition to borders, rock gardens, xeriscapes, and along foundations.
Creeping phlox also grows best in partial shade, making it an excellent choice for woodland edges, woodland gardens, cottage gardens, and patio containers.
This plant adds a beautiful splash of color to any place.
Finally, this plant attracts butterflies, encouraging these attractive pollinators to visit your other plants.