Roadside (Annual) Phlox - Phlox drummondii

Roadside phlox is an annual that is not native to Florida, but widely planted on roadsides throughout the northern half of the state.  It actually is native to Texas, but it thrives in well-drained sunny areas and, thus, makes an excellent roadside wildflower. It is a difficult landscape addition, however, because it is an annual and, like all members of this genus, its seeds "explode" when the seed capsules ripen and next year's phlox plants end up everywhere in the landscape except where they started.
Roadside phlox germinates in early spring and reaches its mature height of about 12 inches by late spring.  Individual plants are thin and rather weak-stemmed. Leaves are linear and yellow-green in color. This is not a showy species for its foliage or when planted alone. In mass, however, it is spectacular.
Flowers come in a wide range of colors - from white to deep crimson, but most are a shade of pink, often with a contrasting center.  All phlox are good nectar sources for butterflies and this species is no exception.  Flowering occurs over a period of about a month, the plants soon wither and die by fall. 
Florida's native phlox are perennials and these make superior landscape plants.  Roadside phlox, however, is a superior choice for roadsides as it rapidly colonizes open areas and thrives in the sunny, often-dry conditions found on most roadways.  Because of this, it is widely seeded by state highway staff involved with Florida's roadside beautification projects. It can't be missed if you travel anywhere in north Florida during April-June.
If you wish to try it in a landscape, use it in large planting beds where it can move about over the years, give it open, sunny conditions, and do not mulch it.  I have had very limited success with it as a mixed wildlower garden specimen as it truly looks best when it can be massed and its annual nature and its method of reseeding make it impossible to mass over time unless it is used in a setting much like those found along roadsides.