Phlox divaricata [floks, dy-vair-ih-KAY-tuh] is a wildflower found natively throughout eastern North America.
It’s often found in fields and forests, where it produces spreading growth.
Phlox divaricata has several common names:
- Wild blue phlox
- Woodland phlox
- Wild sweet William
The plant belongs to the Polemoniaceae family of annuals and perennials.
Wild blue phlox is a popular flower known for its semi-evergreen foliage and bright purple or lavender flowers.
Phlox Divaricata Care
Size and Growth
The name divaricata means “with spreading and straggling habit,” describing the growth of the plant.
- The plant produces a mat of creeping stems that take root as the plant spreads, but it’s not invasive.
- The roots remain weak and easy to remove.
- The low-growing perennial has semi-evergreen foliage.
- The unstalked leaves are about one to two inches long and oval-shaped.
- The stems may reach about 12” to 15” inches tall.
Flowering and Fragrance
Phlox divaricata blooms between April and May.
It produces loose clusters of tubular flowers measuring up to 1.5” inches wide.
The flowers have five petal-like lobes that appear near the tips of the stems in the spring.
The leaves are often lilac, rose, or blue with a slightly fragrant scent.
Light and Temperature
Wild blue phlox is winter hardy in USDA hardiness zones 3 to 8.
Throughout most of North America, the plant should grow easily outdoors.
It prefers partial shade to full shade.
If grown as a potted plant, it should be kept in a room with temperatures between 65° and 75° degrees Fahrenheit (18° – 24° C) during the summer.
Full sun may scorch the leaves of the plant.
It typically only tolerates full sun in cool climates such as USDA hardiness zones 3 and 4.
Watering and Feeding
The plant only requires moderate watering.
Allow the soil to mostly dry out between each watering.
As the plant matures, it may require less frequent watering.
The frequency of the watering also depends on the weather.
Established plants may only need water during periods of drought.
NOTE: Established plants also become partially-drought tolerant.
Fertilizer isn’t needed, but applying a diluted liquid fertilizer during the summer encourages fuller blooms and thicker growth.
Soil and Transplanting
Grow in well-drained soil.
The plant prefers moist organic soil but also grows easily in dry soil and poor soil.
As phlox divaricata is rarely grown as a potted plant, transplanting is typically only needed to stop the spread of shoots.
Established plants may produce shoots that root at the nodes.
Remove the shoots and transplant to other spots in the garden.
After flowering, it’s okay to trim the dead flower stalks to clean up the plant, but it’s not required.
At the start of spring, remove winter-damaged leaves and stems.
How to Propagate Woodland Phlox
Propagate with seed, cuttings, or shoots.
Sharting From Shoots
As mentioned, mature plants may start to produce shoots.
- Carefully dig up the soil around one or more of the leafy shoots.
- Trim the root where it connects to the mother plant.
- Transplant shoots using the same soil that the mother plant grows in.
Starting From Seeds
It’s difficult to obtain seed directly from the plant.
- Purchased seeds should be sown indoors about eight weeks before the last threat of frost at the start of spring.
- Germinate the seeds for several weeks in a dark environment with temperatures around 65° degrees Fahrenheit (18° C).
- Provide even moisture and then plant in rich, moist soil.
- The seedling should appear before the start of spring.
- When leaves start to appear, and the threat of frost is gone, transplant the seedlings outdoors.
Rooting From Stem Cuttings
- Take stem cuttings in the spring or root cuttings in the early fall.
- The cuttings should come from healthy sections of the plant.
- After taking the cuttings, remove the lower sets of leaves.
- Dip the tips in rooting hormone powder to encourage faster growth.
- As with the seedlings, plant the cuttings in rich, moist soil.
- Keep the cuttings indoors in a room with indirect, filtered sunlight.
- The cuttings should take root within one to two months.
- If propagating in the spring, transplant the young plants outdoors.
- If you take root cuttings in the fall, wait until the spring to transplant the cuttings.
Woodland Phlox Pest or Disease Problems
The main threat to phlox divaricata is mildew.
Powdery mildew may develop on the stems and leaves due to overwatering or poor drainage. Learn more in our article about Powdery Mildew on Phlox.
If the soil doesn’t drain after watering, improve drainage by adding a small amount of sand or crushed gravel to the soil.
Cutting the stems back after the flowering season also helps reduce the risk of mildew growth.
Phlox divaricata may attract spider mites, especially in hot, dry environments.
Remove the pests with sprays of water from the garden hose or treat the plant with a commercial pesticide. Neem oil also an option.
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The attractive flowers may also attract pets or small children.
Luckily, the plant isn’t considered harmful or toxic.
Suggested Phlox Divaricata Uses
Phlox divaricata is commonly grown in gardens to provide borders.
Due to the low-growing stems, phlox divaricata also works as a cover for early spring bulbs.