Emerald Blue Creeping Phlox
Blue Flowers
A low growing spring perennial for the front of the border.
Emerald Blue creeping phlox (Phlox subulata ‘Emerald Blue’) is an herbaceous perennial ground cover with blue lavender flowers. It is a cultivar of a plant native to the Eastern United States, where it grows in open clearings and on rocky, sandy sites and slopes. Creeping phlox, known by the latin name Phlox subulata, is also called moss phlox or carpet phlox, and should not be confused with cousin Phlox stolonifera, which can handle more shade. Emerald Blue creeping phlox will form a low, spreading carpet and can stabilize dry, rocky slopes in zones 3-9.
Give Emerald Blue creeping phlox plenty of sunshine (6+ hours), and you will be rewarded with a carpet of delicate 5-petaled flowers in April and May, which attract pollinators and brighten up your garden. This mat-forming ground cover with soft green foliage grows 6-8 inches high, and can spread up to 24 inches wide. Emerald Blue creeping phlox is relatively pest and disease resistant, and it does not suffer from powdery mildew to the same extent as other types of garden phlox. Though not a preferred food for deer, it is a particular favorite of rabbits, who will chew the plant down to the ground.
The soft green foliage of Emerald Blue creeping phlox.
How to Plant and Grow Emerald Blue Creeping Phlox
Emerald Blue creeping phlox (Phlox subulata ‘Emerald Blue’) is covered with lavender-blue flowers in spring.
Location: Select a well-draining site with full sun for best flowering. Emerald Blue creeping phlox prefers a sunny location - it can grow in partial shade but flowering will be diminished.
Soil: Emerald Blue creeping phlox prefers moist, well-draining soil and can tolerate a variety of soil types, including clay and sand. Avoid planting in wet, poorly-drained sites.
Planting: The best time of year to plant Emerald Blue creeping phlox is in the spring or fall, giving the roots time to establish before the onset of extreme hot or cold weather. Phlox is widely available at most nurseries during the spring and may be sold out by the time autumn comes around. Water deeply after planting (for more information on watering, read “How to Water your Plants”.
Spacing: Space Emerald Blue phlox plants 18 inches apart on center (18 inches from the center of one plant to the center of the next plant). Try this handy plant calculator to determine the number of plants required for your garden.
Watering: Keep the soil consistently moist, especially during the first growing season. Once established, Emerald Blue phlox is relatively drought-tolerant, but regular watering during dry periods will promote better flowering (Are you in a drought? Check the U.S. Drought Monitor).
Mulching: Apply a layer of mulch around the plants to help retain moisture, suppress weeds, and maintain a more consistent soil temperature.
Fertilizer: To promote flowering, fertilize in early spring with a balanced, slow-release fertilizer like Plant-tone®.
Division: Phlox subulata can be divided every 2-4 years in the early spring to rejuvenate the plant and control its size. Dig up the entire plant and separate into smaller sections, making sure each section contains both shoots and roots. Immediately replant the divided sections, and share with a neighbor or friend if you have extra!
Garden Ideas for Emerald Blue Creeping Phlox
Rock Garden: Plant Emerald Blue creeping phlox in a rock garden, where it will creep around rocks and create a colorful carpet.
Slopes and Hillsides: Use a mass planting of Emerald Blue creeping phlox to cover sunny slopes or hillside, preventing soil erosion while adding a burst of color.
Edging: Use Emerald Blue creeping phlox as an edging plant along walkways, sidewalks, or driveways, where it can create a bright and well-defined boundary.
Rock Wall: Plant Emerald Blue creeping phlox on the top of a rock wall, where it can cascade over the stone and soften the hard edges of the landscaping.
Drifts and Mass Plantings: Plant Emerald Blue creeping phlox in large drifts or masses for a stunning display of color. This is particularly effective for larger garden spaces or areas where a bold impact is desired.
Perennial Border: Plant Emerald Blue Creeping Phlox at the front of the border for a tidy and well-defined edge. Arrange taller perennials behind, selecting plants with staggered blooming times to guarantee a constant display of interest throughout the entire growing season.
Use Emerald Blue creeping phlox as a no-mow ground cover on a sunny slope.
Emerald Blue creeping phlox (Phlox subulata ‘Emerald Blue’) softens the hard edges of a concrete curb.
Planting Companions for Emerald Blue Creeping Phlox
Autumn Angel® Encore® Azalea (Rhododendron ‘Robleg’): A dwarf, compact azalea for full sun, with white flowers and dark green leaves.
Catmint (Nepeta): A spring-flowering perennial with spiky purple flowers and silvery blue leaves.
Helen von Stein Lamb’s Ears (Stachys byzantina ‘Helen von Stein’): Create a pleasing contrast of color and texture by planting this silvery ground cover next to creeping phlox.
Pigsqueak (Bergenia species): The large leaves of this spring-flowering perennial ground cover contrast nicely with the fine-textured foliage of creeping phlox.
Southern Wood Fern (Dryopteris ludoviciana): An adaptable fern for zones 8-10 that can handle full sun.
Why Did My Creeping Phlox Stop Blooming?
Age of the Plant: Creeping phlox tends to be more vigorous during the first few years of growth. As the plant ages, flowering may decrease. Divide and replant section of the plant every 2-4 years to rejuvenate the plant and encourage more blooms.
Sunlight: Lack of sunlight can result in reduced blooming. Ensure that the plant receives full sun (6+ hours of direct sunlight per day) to promote flowering. Creeping phlox will tolerate light shade, but flowering will be diminished.
Soil Conditions: Creeping phlox prefers well-draining soil. Compacted, poorly draining soil can lead to sparse flowering. Amend the soil with organic matter, like compost or Leaf-gro®, to improve drainage.
Nutrient Levels: A nutrient insufficiency can impact flowering. Fertilize creeping phlox with a balanced, slow-release fertilizer (like Plant-tone®) in early spring.
Pests and Diseases: Aphids, spider mites, and powdery mildew are common problems for creeping phlox, and can stress the plant and cause diminished flowering. Keep an eye out for these problems, and treat issues promptly.
Environmental Stress: Extreme weather conditions, such as drought or excessive heat, can stress the plant and affect blooming. Ensure that the phlox is adequately watered during dry periods.
Overcrowding: If creeping phlox is overcrowded or competing with other plants, it may not bloom as prolifically. Consider thinning out the plant or providing it with more space for better health.
Is Emerald Blue Creeping Phlox Invasive?
Creeping phlox is not considered an invasive plant in the United States (check out the USDA’s database of Invasive and Noxious Plants). Emerald Blue creeping phlox is a cultivar of a plant native to the Eastern United States. It does not self-seed, and will stay within its designated spot in the garden, making it a desirable choice for a controlled ground cover.
In the right conditions, such as full sun and well-draining soil, creeping phlox can thrive and spread rapidly. Creeping phlox spreads by stolons (above-ground, creeping roots), making it very easy to thin out and keep in check.
