Phlox pilosa L.

Prairie Phlox, Downy Phlox

Phlox pilosa plant

Family - Polemoniaceae

Stems - To +40cm tall, herbaceous, erect, typically simple below but branching at inflorescence, single or multiple from base, from taproot, simple to glandular pubescent.

Phlox pilosa stem

Leaves - Opposite(maybe a few alternate bracts in inflorescence), sessile, linear to linear-lanceolate or ovate, entire, acute to attenuate, rounded at base, to +/-5cm long, +/-1cm broad, pilose to glandular pubescent, with single prominent midrib.

Phlox pilosa leaves

Inflorescence - Terminal and axillary cymes, many flowered (+/-50). Peduncles and pedicels densely glandular pubescent. Pedicels to +/-9mm long. Flowers often subtended by linear-lanceolate bracts.

Phlox pilosa inflorescenceInflorescence.

Flowers - Corolla various shades of purple or rarely white, 5-lobed. Corolla tube to 1.5cm long, 2mm in diameter, with multicellular hairs externally. Corolla lobes spreading, to 1.5cm long, 5-8mm broad obovate, glabrous. Stamens 5, adnate at different levels in corolla tube, mostly included. Anthers yellow, 1.5mm long. Style 1-3mm long. Stigma 3-lobed. Lobes -1mm long. Ovary glabrous, green, 1.1mm long, superior, 2-3-locular. Calyx densely glandular pubescent, accrescent. Calyx tube to 2mm long, 5-lobed. Lobes linear-attenuate, 8mm long, 1mm broad, connected by scarious tissue for 2-3mm above calyx tube, often with some purplish coloring.

Phlox pilosa calyxCalyx.

Phlox pilosa flowers

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

Habitat - Rocky or dry open woods, valleys, thickets, meadows, prairies, glades.

Origin - Native to U.S.

Other info. - This is a popular little plant because of its striking floral displays and the easy manner in which it can be grown. The plant takes readily from seed and produces much seed every year. The plant itself is perennial.
This is an extremely variable plant in nature with no fewer than 6 varieties and forms in Missouri alone and more elsewhere. The varieties are based on the type and amount of pubescence on the calyx and subtending bracts, the shape and size of the leaves, and of course the flower color. I am not going to go into all the varieties and forms here because many of them integrate, further complicating the issue.
This plant is sometimes mistaken for Phlox divaricata L. but this latter species blooms slightly earlier in the year, grows in moist places, spreads by horizontal runners, and has more bluish flowers.

Photographs taken on Taum Sauk Mountain, MO., 5-23-03 and 5-31-03.