If you live in eastern North America and seek blue flowers for a dappled-shade native plant garden, then woodland phlox is an excellent choice. A spreading mat of lance-shaped leaves supports clusters of slightly fragrant tubular flowers at the tips of sticky, hairy stems. The flowers, each with five small flat petals, vary widely in their blue tones. Some petals will be light purple, violet, violet-blue, and even a lighter blue; still, others will be rosy lavender, pale pink, or white.
Woodland phlox should be planted in the spring so it has time to spread (it won't grow as quickly as creeping phlox) and produce fragrant flowers that bloom in clusters during April and May in its native range.
|Common Name||Woodland phlox, wild blue phlox|
|Botanical Name||Phlox divaricata|
|Plant Type||Herbaceous, perennial|
|Mature Size||9-12 in. tall, 9-12 in. wide|
|Sun Exposure||Partial, shade|
|Soil Type||Moist, well-drained|
|Flower Color||Purple, blue|
|Hardiness Zones||3a-8a (USDA)|
|Native Area||North America|
Woodland Phlox Care
Woodland phlox is a perfect native-plant option for gardens with dappled shade. It belongs to the Polemoniaceae family, as does Jacob's ladder (Polemonium caeruleum). Since this perennial grows wild, you may not be as familiar with it as you are with the commonly cultivated types of phlox, but it belongs to the same genus.
Woodland phlox grows in flecked patches of shade in its native woodlands in North America from Ontario to Louisiana and westward to Minnesota. The species name divaricata translates from Latin as "spreading," but it is not considered an invasive plant.
Most gardeners treat it as a flowering ground cover or edging plant. A potential drawback of using it as a ground cover is that it does not stay as short as many of the more conventional ground covers. Woodland phlox is known to be a plant that attracts butterflies. It is also considered a flower worth including in hummingbird gardens.
Woodland phlox grows best in checkered shade so do not try to grow it in full sun unless you live in a cool climate. Find a location in your landscaping that will best mimic the flower's natural habitat, providing this perennial with, at most, filtered sunlight.
Try to mimic the rich, moist soil that you'd find in woodland conditions. The soil should also drain well for best results. The plant, however, is very adaptable and will tolerate dry, clay soil, especially when it is established.
Keep the soil of woodland phlox evenly moist, but never waterlogged at all times. An application of landscape mulch will help retain moisture in the location that you have selected.
Temperature and Humidity
This plant can handle a good deal of humidity but doesn't like overly hot temperatures, so take care to keep it in dappled shade. Anything that mimics the conditions on the forest floor is best.
In the wild, woodland phlox is naturally fertilized when the leaf litter in the forest breaks down to become leaf mold. Keep it fertilized in your landscape by working compost into the ground around your plant annually in spring.
Types of Phlox
There are many other attractive types of phlox. Popular cultivars of woodland phlox and other phlox species include:
- P. divaricata 'Blue Moon', a cultivar with large violet-blue flowers
- P. divaricata 'Fuller's White', a cultivar with white flowers
- P. stolonifera (Creeping phlox), a low-growing, mat-forming ground cover
- P. subulata (Moss phlox), a creeping phlox that forms a carpet of color in the spring
- P. paniculata (Garden phlox, tall phlox), panicles of blooms atop tall stalks in the summer
Lightly cut back stems after the plant flowers to clean up the garden's appearance. Prune in the late summer and fall if you do not want the plant to reseed. Be aware that if phlox stems flop over onto the ground, there will be leafy shoots that begin to root at the nodes and grow increasing the colony's spread.
Propagating Woodland Phlox
There are several options for propagating woodland phlox. It can be grown from seed, mature plants can be divided in the spring or early fall, it can be propagated from stem cuttings in the spring, or root cuttings in early fall.
To divide the plant in the spring or early fall:
- Use a shovel with a sharp edge and detach a section of rooted stems at the point where you would like to divide the plant. Make sure that each division has a good amount of roots attached to it.
- Dig around the division until you can easily lift it out of the ground without ripping off any roots.
- Transplant the divisions in a new location at the same depth as the original plant. Water them well and keep them moist until you see new growth.
To propagate with stem cuttings in the spring:
- Using clean, sharp pruners or a knife, cut a stem from the base of the plant. Select one that has three or four sets of leaves. Remove the lower leaves from the cutting.
- Dip the cut ends in rooting hormone. Plant the cuttings in a pot filled with moist potting mix. Place the cuttings in an outdoor location with indirect sunlight.
- Cuttings should root in four to eight weeks. Check for roots by very gently tugging on them. When you feel resistance, roots have likely formed.
- Transplant them in the garden soil at the same depth as the original plant.
Root cuttings taken in the early fall are handled similarly to stem cuttings but you can transplant them into garden soil right away. Keep them evenly moist in the absence of rain and cover them with a layer of mulch for winter protection. Mark the location because you won’t likely see any growth in the fall but the plant should take off the next spring.
How to Grow Woodland Phlox From Seed
The seeds of woodland phlox need 60 days of cold stratification to germinate. This can be either done naturally outdoors or artificially in the fridge:
Starting seeds by natural stratification:
In late fall or winter, sow the seeds in a well-marked, weed-free location. Cold weather and rain or snow provide the perfect environment to break the seed dormancy so you don’t need to do anything. In the spring, seedlings will emerge on their own.
Starting seeds by artificial stratification:
Place seeds and a stratification medium (damp paper towel, coffee filter, sand, or vermiculite) in a sealed plastic bag and store them in the refrigerator at a temperature between 33 and 40 degrees Fahrenheit. Use about equal parts of sand and seed and keep the medium damp but not wet. As soon as the ground can be worked in the spring, sow the seeds outdoors and keep the soil moist at all times. The seedlings should emerge within a few weeks.
Woodland phlox fares well during winter within its hardiness zones without much care, but mulching before the first frost will protect the plants in colder regions.
Common Pests and Plant Diseases
Woodland phlox is susceptible to spider mites and powdery mildew. As with any plant vulnerable to powdery mildew, aeration through appropriate spacing can help. It also helps to give woodland phlox a haircut after it has finished blooming since rampant growth can inhibit air circulation.
How to Get Woodland Phlox to Bloom
Woodland phlox is unique in that it requires pollination from long-tongued insects to bloom. Therefore, you want to introduce or encourage certain insects, including bumblebees, tiger swallowtails, sphinx moths, hummingbirds, and skippers. It can be helpful to plant a variety of flowers nearby that will draw these creatures to the area.
Can woodland phlox grow indoors?
This plant rarely grows well as a potted plant because it's more of a ground cover.
How long can woodland phlox live?
The original plant will readily spread in the right conditions, so a stand of woodland phlox can live for 10 years or more.
What is the difference between woodland phlox and dame's rocket?
Dame's rocket is an invasive plant that looks quite a bit like woodland phlox. To tell them apart, look at the petals—woodland phlox has five petals, while dame's rocket has four.
Phlox divaricata. NC State Extension Service Plant Toolbox