2. Phlox bifida L.C. Beck (cleft phlox, sand phlox)

P. bifida ssp. stellaria (A. Gray) Wherry

P. bifida var. stellaria (A. Gray) Wherry

Pl. 494 a, b; Map 2253

Plants perennial herbs with woody, often branched rootstocks, forming open mats or low, loose mounds, with short primary rhizomes. Vegetative stems spreading to slightly ascending, sometimes initially forming tufts of long leaves at congested nodes (but the nodes becoming uncongested at maturity), these leaves otherwise morphologically similar to those of the flowering stems. Flowering stem branches numerous, produced from the vegetative stems, 4–30 cm tall, with 4–6 nodes, erect or ascending, usually densely pubescent with curved or crinkled, multicellular hairs, these often all or mostly gland-tipped, at least toward the stem tip (and inflorescence). Leaves all opposite, the blade typically variable on a given plant, those of the largest leaves 2.5–5.5 cm long and 1–4 mm wide, linear to narrowly lanceolate, the surfaces and margins of the uppermost leaves moderately to densely pubescent with curved or crinkled, multicellular, often gland-tipped hairs, progressively less hairy toward the stem base, those of the lowermost leaves often glabrous or nearly so. Inflorescences relatively few-flowered, short and appearing as clusters, with 3–25 flowers or occasionally reduced to solitary flowers. Flower stalks 3–30 mm long. Calyces 5.0–9.5 mm long, the lobes each tapered evenly to a short sharp extension of the midnerve, usually glandular-hairy. Corollas pale bluish purple or light lavender to white, the tube 8–14 mm long, glabrous externally, lacking a basal constriction, the lobes 5.0–12.5 mm long and 3–8 mm wide, obovate, with a conspicuous apical notch 1.5–5.0 mm deep. Stamens with the filaments 5–11 mm long, the anthers positioned from below to at or above the stigma at the mouth of the tube (sometimes 1 or 2 slightly exerted). Style 5–10 mm, the stigmas 0.5–1.0 mm long. 2n=14. March–May.

Scattered in the Ozark Natural Division, northward locally to Linn and Marion Counties; also known from a single collection from Dunklin County (Iowa to Oklahoma and Arkansas east to Michigan and Tennessee). Glades, rocky slopes in mesic to dry upland forests, bases, ledges, and tops of bluffs, and banks of streams and rivers; also roadsides.

This species is sometimes cultivated as an ornamental and occasional occurrences in Missouri may represent naturalized rather than truly native plants. Two infraspecific taxa have been widely recognized within P. bifida: ssp. bifida and ssp. stellaria. The latter name has been applied to material with nonglandular inflorescence pubescence and somewhat less deeply notched petals. The vast majority of Missouri populations are assignable to ssp. bifida, but a minority may be considered ssp. stellaria. In our area, nonglandular plants tend to occur adjacent to populations with glandular pubescence (often in relatively thin-soiled areas) or in mixed populations. The author does not view infraspecific taxon recognition to be warranted, although P. bifida does exhibit interesting morphological and ecological variation across its range that requires more detailed study at the population level.