Davy’s or Monterey centaury

Centaurium exaltatum (Grisebach) W. Wight var. davyi Jepson, Man. Fl. Pl. Calif., 762. 1925; C. davyi (Jepson) Abrams

Herbs annual, (2–)5–30(–50) cm. Stems 1–10, simple (small plants) or few-branched ± throughout. Leaves: basal absent or occasionally persisting at flowering, similar to cauline; cauline blades elliptic-oblong to ovate, 8–26 × 3–8(–13) mm, apex obtuse to acute. Inflorescences completely monochasial or occa­sionally proximally dichasial, ± racemoid cymes; pedi­cels (2–)4–25(–55) mm. Flowers 5-merous; calyx 8–10 mm; corolla 12–17 mm, lobes ovate-oblong, 3–7 mm, keeled (uniquely in this species in the flora area), apex obtuse; stigmas 2, widely fan-shaped. Seeds dark brown.

Flowering spring–summer. Moist coastal bluffs, inter­dunal depressions, open woods, sometimes in ultra­mafic soils; 0–1000 m; Calif.

The name Centaurium muehlenbergii has some­times been misapplied to Zeltnera davyi, with true Z. muehlenbergii then being called C. floribundum (J. S. Pringle 2010b).

The distinctly keeled calyx lobes cause the calyces of Zeltnera davyi to appear greater in diameter than those of related species and ovoid to ellipsoid rather than nearly cylindric. The combination of this calyx mor­phology and the proportionately wide, relatively deeply pigmented corolla lobes (usually evident in herbarium specimens) gives the flowers of Z. davyi a distinctive aspect.

Zeltnera davyi and Z. muehlenbergii are sometimes similar in habit. Medium-sized plants of Z. davyi are usually several-stemmed from the base, whereas that pattern is much less common in Z. muehlenbergii. Zeltnera davyi usually differs from Z. muehlenbergii in the presence of elliptic to ovate leaves over 5 mm wide (except on the smallest plants) well into the inflorescence; consistently present pedicels 4–30 mm long; calyx lobes with keels proximally 0.3–0.6 mm wide; and ovate-elliptic corolla lobes 3–7 × 2–3 mm. In Z. muehlenbergii, elliptic to narrowly ovate leaves, when present, are usually limited to the proximal one-third or less of the plant, with the distal leaves being narrower, and the corolla lobes are elliptic-oblong, 2–7 × 1–2 mm (J. S. Pringle 2010b).