Pluchea odorata (L.) Cass., sweetscent, salt marsh fleabane, shrubby camphorweed. Annual or perennial herb, rhizomatous, fibrous–rooted, several–stemmed at base, ascending to erect, 25—120 cm tall; shoots short–villous and glandular–hairy, the glandular hairs minute, colorless, spheric and short–stalked to sessile, strongly spicy; rhizomes yellowish brown.
Stems cylindric, to 4 mm diameter.
Leaves helically alternate, simple, short–petiolate, without stipules; petiole < 6 mm long, ± winged; blade ovate to broadly elliptic, 40—135 × 25—70 mm, broadly tapered at base, shallowly serrate with short–pointed teeth on margins, acute to obtuse at tip, pinnately veined with principal veins raised on lower surface, upper surface sparsely short–villous and glandular with sessile to subsessile glandular hairs in shallow pits, lower surface more densely hairy.
Inflorescence heads, in terminal, paniclelike arrays of many heads, ± flat–topped, head discoid, ca. 4 mm across, with many, slender, pistillate peripheral flowers and < 16 staminate central flowers, bracteate, tomentose and oily glandular–hairy; bract subtending peduncle or branchlet leaflike, 3—12 mm long, decreasing upward, the bract subtending peduncle typically absent; peduncle 2.5—7 mm long, tomentose and oily–glandular; involucre ± U–shaped at anthesis with top narrower than base but expanding in fruit, 4.5—6.5 × 3.5—4.5 mm, phyllaries ± 25 in several series, outer phyllaries acute–ovate, green sometimes with lavender margins near tip, sometimes keeled, tomentose and glandular–hairy, inner phyllaries lanceolate or oblong to linear, green with lavender approaching tip, sometimes with green midvein, villous to glabrous and ciliate at acute tip; receptacle slightly domed or flat, without bractlets (paleae).
Peripheral flower pistillate, radial, slightly exserted beyond involucre, ca. 0.4 mm across; calyx (pappus) of 12–15 capillary bristles in 1 whorl, bristles ± 4.5 mm long, whitish; corolla 3—4–lobed, narrowly cylindric, 4.5 × 0.1 mm, white with rose–pink to purple lobes, glabrous, lacking glands; lobes minute; stamens absent; pistil 1; ovary inferior, narrowly inversely conic–fusiform, 1 × 0.3 mm, pubescent and minutely glandular with spheroidal glands, 1–chambered with 1 ovule; style slender, 4—4.7 mm long, 2–branched, the branches ± 0.9 mm; stigmas linear, lavender, minutely papillate.
Central flower functionally staminate, appearing bisexual but style branches undivided and sterile, radial, slightly exserted beyond involucre, ca. 1 mm across; calyx (pappus) of 15—20 capillary bristles in 1 whorl, bristles ± 4.5 mm long, whitish; corolla 5–lobed, cylindric, 4.5—5 mm long, greenish white or with upper portion rose to purple, with conspicuous colorless spheric glands on upper throat and lobes; tube cylindric, ca. 2.5 × 0.5 mm; throat ± 0.7 mm long, expanding to 0.7 mm wide, glabrous; lobes erect; stamens 5, fused to midpoint on corolla tube, partially exserted; filaments fused midway to tube, ± 1.6 mm long; anthers fused into cylindric surrounding style, basifixed, dithecal, ± 1.9 mm long + short, slender tails at base, pinkish or purple, longitudinally dehiscent; pollen whitish; pistil 1; ovary inferior, inversely conic, 1 mm long, sterile; style exserted, stout, undivided at tip, exposed upper style pink–rose and papillate.
Fruits cypselae, narrow, 4—5–ribbed, 1—1.2 mm long, brown with tannish ribs and base, strongly short–strigose and with short, viscid glandular hairs; pappus bristles ± 13, 3.5—4(—7) mm long, tannish at base, white approaching tip.
A. C. Gibson & B. A. Prigge