Erect sparingly branched annual herb to 2 m tall; stems yellowish to slightly reddish, terete, scarcely striate, glabrous. Leaves opposite; blades deltoid to broadly ovate, to 10 cm long and 11 cm wide, the base broadly rounded to truncate, prominently acuminate and trinervate, the margins closely serrate-dentate, the apex shortly and abruptly apiculate, the upper surface with sparse short coarse pubescence, the lower surface densely covered with numerous oblong or reniform glands; petioles slender, to 6 cm long. Inflorescence a lax profusely branching elongate panicle with paniculate branches, the ultimate branches 4-20 mm long, glabrous. Heads ca. 7 mm high, slender, with mostly 8-14 florets; involucral bracts ca. 20, subimbricate, in 3-4 series, lanceolate to linear-lanceolate, 1-7 mm long, the apex sharply acute, the margins scarious, the outer surface bicostate, glabrous; corolla whitish, 4-5 mm long, slender, narrower above, glabrous except for a few glands on the lobes, the lobes minute; style branches filiform, tapering to the tip. Achenes 1.5-2.0 mm long, densely covered with small bristles; carpopodium prominent; pappus of 30-40 bristles with minutely scabrellous margins. Pollen mostly 20-25 microns in diameter, micropapillose.
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