Creeping phlox (Phlox Subulata) is perennial groundcover. It's popular for its early spring, small flowering clusters. Phlox come in a variety of flower colors and the foliage remains green throughout most of the year. Grown in masses in edgings, cracks, or rocks they make a commanding landscape presence. They are a good plant to use with other spring flowers such as tulips and daffodils.
Phlox are best grown in United States Department of Agriculture (USDA) hardiness zones 3 to 9. Phlox produce small flowers in dense clusters. The plant can reach a height of 6 inches and can spread as far as 2 feet. The flowers have five petals and cluster at the end of the very short stem. It has semi-evergreen "needle-like" foliage that is prickly to the touch. In the spring, it is medium to dark green but can change to a yellow-green during the hottest part of summer or the cold of the winter.
Phlox prefer full sun, well drained sandy soil, with a pH of 6.8 to 7.7 Fertilize every few weeks with a liquid fertilizer. After the phlox stops flowering, prune back the foliage to encourage the development of a denser plant. If you want to divide the plants, it is best to do it in the spring after flowering.
Uses in the Garden
Due to the fact that the phlox remain short and thick, they are primarily used as groundcover. They are used in rock gardens or on slopes to prevent erosion but mostly to show off the vivacious color. They can also be used along paths, at foundations, or at the edge of flower beds. Phlox are also known to attract butterflies.
The most severe problem for phlox is the foliar nematodes. This plant pathogen has a large range of hosts. The key diagnostic feature is leave damage and the presence of little roundworms. It spreads by contact between plants in the presence of water.
There are a couple ways to manage this problem. First, move the plant to a remote area for observation. Either treat or throw away infected plants. Minimize wetness to the foliage to reduce the spread. Move and destroy infected leaves and remove all dried leaves during fall cleanup. Insecticidal soap can be applied when symptoms start to show. Finally, foliar nematodes are easily killed by heat. This can be done by removing the infected leaves and soaking the rest of the plant in hot water (120 to 140 degrees Farenheit) for 10 minutes. Be sure and monitor this procedure because if the water is too hot, or you soak too long, you can kill them. Right after the hot water, dunk them in cold water for five minutes, just long enough for the plant tissue to cool. Drain the pots immediately.
Spider mites are also a problem insect for phlox. If the infestation is found early enough an insecticidal soap can be somewhat effective. If it's more severe, check with your local nursery for Kelthane, a miticide, specifically for the mites. Apply the spray early in the day, when it's cooler. Don't spray during the heat of the day or you can damage foliage.
Phlox translates from the Greek as "a flame." Subulata translates as "awl-shaped," referring to the needle-like leaves.