Phlox pilosa L.

Prairie Phlox


CC = 6
CW = 3
MOC = 75

© DETenaglia

Family - Polemoniaceae

Habit - Perennial forb with taproot and slender rhizomes.

Stems - Flowering stems ascending to erect, to 60 cm tall, typically 1-3, with 6-17 nodes, usually simple below but branching at inflorescence, moderately to densely pubescent with multicellular, spreading to curved or crinkled hairs, some or all of these sometimes gland-tipped. Vegetative stems not produced or, if present, then shorter than but otherwise similar to the flowering ones.

Phlox_pilosa_stem.jpg Stem and node.

© SRTurner

Phlox_pilosa_stem2.jpg Stem and subopposite node.

© SRTurner

Leaves - Opposite, the uppermost occasionally subopposite, sessile, simple, the the blades linear to lanceolate or ovate toward the tip, angled or tapered to a sharply pointed tip, angled or tapered at the base, the largest 3.5-8.0 cm long and 2-20 mm wide, with single prominent midrib, the margins usually short-hairy, the surfaces sparsely to densely hairy, the hairs nonglandular or gland-tipped, the secondary veins obscure, pinnate and not forming conspicuous loops.

Phlox_pilosa_leaf1.jpg Leaf adaxial.

© SRTurner

Phlox_pilosa_leaf2.jpg Leaf abaxial.

© SRTurner

Phlox_pilosa_leaves.jpg Pressed leaves.

© DETenaglia

Inflorescences - Terminal and axillary domed panicles, typically with 15-60 flowers. Peduncles and pedicels densely glandular-pubescent. Pedicels to 9 mm long. Flowers often subtended by linear-lanceolate bracts.

Phlox_pilosa_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Calyces 7-14 mm long, the lobes slender, long-tapered to sharply pointed tips, often with some purplish coloring, glandular- or nonglandular-hairy. Corollas pink to light purple, rarely white, the tube 10-16 mm long, usually moderately to densely hairy externally, with a slight constriction 1.5-3.0 mm above the base, the 5 lobes 6-14 mm long and 4-11 mm wide, obovate or less commonly oblanceolate, rounded at the tips, sometimes with an abrupt, short point at the very tip. Stamens with the filaments 4-15 mm long, the anthers positioned above the stigma within the tube, not exserted. Style 0.4-1.0 mm long, the stigmas 0.9-1.6 mm long. Ovary glabrous, green, 1.1 mm long, superior, 2-3-locular.

Phlox_pilosa_calyces.jpg Calyces.

© SRTurner

Phlox_pilosa_corolla.jpg Corolla. Anthers usually visible at throat.

© SRTurner

Phlox_pilosa_tube.jpg Corolla tube, with glandular hairs.

© SRTurner

Phlox_pilosa_white.jpg Pale variant.

© SRTurner

Flowering - April - June, sometimes again in the late fall.

Habitat - Glades, savannas, prairies, forests, bluffs, pond margins, streambanks, fens, pastures, fields, railroads, roadsides.

Origin - Native to the U.S.

Lookalikes - Other species of Phlox, especially P. divaricata.

Other info. - This attractive species is fairly common throughout most of Missouri. Its main U.S. distribution is within a wide band running north to south within the Midwest, though more scattered populations are also found out to the Atlantic Coast. It also ranges into Canada and Mexico. The shape of the flowers readily identifies the plant as a phlox, but it can sometimes be confused with other species in the genus. Characters to look for include hairy stems and leaf margins, and lower leaves which are typically narrow. The anthers are usually positioned close enough to the throat of the corolla tube to be visible without dissecting the flower. The long corolla tube is pubescent externally, which easily distinguishes this plant from its closest lookalike, P. divaricata.

The species is highly variable and has been subdivided into numerous infraspecific forms, three of which are recognized in Missouri. Plants with nonglandular hairs on the inflorescence and calyces are ssp. fulgida. Plants with glandular hairs on these structures can be either ssp. Ozarkana, which has shallowly cordate upper leaves and most stem hairs with glandular pubescence, or ssp. pilosa, which has rounded leaf bases and glandular stem hairs only toward the tip.

The species is showy and easily grown from seed. It is sometimes cultivated as an ornamental, and deservingly so.

Photographs taken on Taum Sauk Mountain, MO., 5-23-03 and 5-31-03 (DETenaglia); also at Danville Conservation Area, Montgomery County, MO, 4-28-2016 (SRTurner).