Vernonia baldwinii Torrey, western ironweed, baldwin ironweed. Perennial herb, robust, rhizomatous, rosetted, 1–stemmed at base, in range to 180 cm tall; shoots with only cauline leaves, foliage not aromatic when crushed.
Stems cylindric, to 9 mm diameter, internodes < 35 mm long, puberulent and short–hairy, not gland–dotted.
Leaves helically alternate, simple, short–petiolate, without stipules; petiole indistinct from blade, hemicylindric, to 5 mm long; blade ovate to lanceolate, 50—165 × 19—75 mm, tapered at base, serrate and minutely serrate on margins, acute to acuminate at tip, pinnately veined with principal veins raised on lower surface, upper surface dull green, puberulent and short–hirsute, lower surface minutely strigose and gland–dotted with sessile heads in shallow pits, midrib (principal veins) with stalked, 2–armed hairs.
Inflorescence heads, in terminal and axillary, ± flat–topped, cymelike array of several—many heads, head discoid, 12—19 mm across, with 25—30 showy, bisexual flowers, outer flowers spreading, bracteate, pubescent with short unbranched and 2–armed hairs; bract subtending array leaflike, narrowly elliptic, < 15 mm long, sometimes 3–toothed; bract subtending lateral branch and peduncle awl–shaped, ca. 2 mm long, decreasing upward; peduncle ridged, < 20 mm long, resin gland–dotted, short–hairy; involucre bell–shaped, 6—6.5 × 4—5 mm, phyllaries 45—65 in several series, unequal, the outermost phyllaries awl–shaped, 1 mm long increasing to middle phyllaries ovate, ± 4 mm long and inner phyllaries oblong, ca. 6 mm long, green with deep purple on exposed tip, raised midvein above midpoint, and edges, short–ciliate on margins, exposed tissue resin gland–dotted; receptacle flat and narrow, lacking bractlets (paleae), having crownlike teeth to 0.5 mm long surrounding each ovary, the ridges white and puberulent.
Disc flower radial, 6—7 mm across, 13—15 mm long; calyx (pappus) of 20+ free, colorless, narrow scales in whorl (outer series) and ca. 50 bristles in whorl (inner series), the scales, stiff, 0.2— < 1 × 0.1—0.2 mm, the bristle ring fused to scales, 4.6—7 mm long and exserted from involucre, purplish red; corolla 5–lobed, ± trumpet–shaped (salverform); tube + throat narrowly funnel–shaped, with scattered resin glands, tube 5–sided, ca. 4 × 0.6 mm, white to pale purple, throat 2.5—3 mm long, 1 mm wide at orifice, light violet changing to violet above midpoint; lobes strap–shaped, ca. 3 × 0.5 mm, violet, acute at tip; stamens 5, attached to top of corolla tube; filaments ± 2.2 mm long, lavender white; anthers fused into cylinder surrounding style, basifixed, dithecal, ± fully exserted, arrow–shaped (sagittate), ca. 4 mm long with appendages and tails, sacs and linear tails white, appendages erect, lanceolate, ± 0.8 mm long, densely covered with resin–producing glandular hairs, longitudinally dehiscent; pollen colorless; pistil 1; ovary inferior, narrowly wedge–shaped to columnar and ca. 7—8 ribs and angled, 1.2—1.4 mm long, white, having resin glands and cobwebby–hairy along ribs; nectary disc surrounding base of style, 0.3 mm long, white, producing copious thin nectar; style exserted to 5 mm, 12—13 mm long, 2–branched, white at base to below fork, light violet above and violet branches, the stigmatic branches fully exposed, ascending later strongly recurved, 3.5—4 mm long, conspicuously short–hairy.
Fruits cypselae (achenes) columnar, conspicuously 10–ribbed, 3—3.2 × 0.6—0.75 mm, brownish with purple dots in furrows, having white callous at base; pappus of 20+ narrow scales in whorl (outer series) and ca. 50 bristles in whorl (inner series), the scales, stiff, light brown, 0.2— < 1 × 0.1—0.2 mm, the bristle ring fused to scales, 4.6—7 mm long, light brown.
A. C. Gibson