Perennial herb 25 - 60 cm tall Leaves: opposite, stalkless, longer than wide, and abruptly or gradually narrowed to a sharp, stiff point. The lower leaves are linear and almost hairless, while the larger leaves, above the middle of the stem, are lance-shaped, 4 - 9 cm long, 0.3 - 1 cm wide, and more evenly hairy. Inflorescence: terminal, loose and open branched, covered with obvious glandular hairs, and having twenty to fifty or more flowers with bracts scattered throughout. The two lowest branches of the inflorescence are at least 1 cm long. Flowers: short-stalked (stalks 4 - 8 mm long), pink or purple, sometimes white or occasionally lavender, 1.5 - 2 cm wide, radially symmetric, with a slender tube, and abruptly flared lobes. Sepals: five, 0.8 - 1.2 cm long overall, but fused for up to half their length, then separating into awl-shaped lobes with 1 - 2 mm long, stiff, bristle tips. Petals: five, but fused into a 0.8 - 1.5 cm long, hairy tube (sometimes with a few glandular hairs), then separating into 1.1 cm long, 0.7 cm wide, inversely egg-shaped lobes with rounded or abruptly short-pointed tips. Stamens: five, with filaments attached at different heights along the inside of the petal tube, but never extending beyond the petal tube. Pistil: with a single, three-chambered, superior ovary; and three, short (1.5 - 4 mm long, usually shorter than stigmas or ovary), fused styles, which separate above the middle into three, linear stigmas. Fruit: a three-valved, three-chambered, egg-shaped capsule with one (rarely two), relatively large (up to 6 mm long), ellipsoid seed per chamber. Stems: slender, with horizontal, non-rooting, non-leafy shoots, and normally a single, erect, fertile shoot (with leaves and flowers), which is unbranched below the inflorescence, and covered with long, soft, non-glandular hairs.
Similar species: Phlox pilosa ssp. pilosa is one of five subspecies of P. pilosa in eastern North America. These five subspecies can be distinguished by the hairs of the inflorescence. There are only two subspecies in the Chicago Region, this one, which always has glandular hairs in the inflorescence, and P. pilosa ssp. fulgida, which never has glandular hairs, but rather multicelled, long, silky hairs in the inflorescence.
Flowering: May to August
Habitat and ecology: Very characteristic of sandy black oak savannas and prairies.
Occurence in the Chicago region: native
Notes: This subspecies is known to attract many insects, including long-tongued bees, and especially butterflies.
Etymology: Phlox is the Greek word for flame. Pilosa means covered in soft, long hairs.