Annual herb with a slender taproot, erect, 40–90 cm. tall, with few to numerous opposite branches diverging at c. 45 degrees, the uppermost pair of branches with a sessile to shortly (to c. 3 cm.) pedunculate inflorescence between. Stem and branches quadrangular, thinly to more or less densely upwardly-appressed pilose. Leaves narrowly lanceolate to broadly elliptic or ovate, subacute to acuminate, those of the main stem and large branches 2.5–10 × 0.8–4.5 cm., moderately white pilose on both surfaces or more densely so below, cuneate or attenuate at the base into a distinct, 3–15 mm. long petiole; superior leaves of branches smaller, generally sessile. Inflorescence considerably lengthening in fruit, (1.5) 2.5–16 × 1.5 × 2.5 (3) cm., axis more or less densely furnished with flexuose whitish hairs, formed of numerous densely set partial inflorescences comprising three or four fertile flowers, two central and solitary and the others subtended by a modified sterile flower on each side; partial inflorescences soon falling in fruit, the persistent bracts strongly deflexed. Bracts broadly ovate, 4.5–5.5 mm. long, furnished with appressed white hairs, rather abruptly acuminate, finely aristate with the long-excurrent midrib. Bracteoles of the partial inflorescences broadly cordate-ovate, 5–7 mm. long, ciliate or pilose, hyaline with the darker midrib excurrent in a fine arista up to 1.5 mm. long; bracteoles of secondary triads deltoid-ovate, c. 7–9 mm. long, pilose along the midrib with a rigid arista; bracteoles of the sterile flowers narrower, densely pilose along the midrib with multicellular hairs, the arista very long (almost as long as the lamina), more solid in fruit and finally up to c. 12 mm. long. Sterile flowers of 2 rapidly developing linear, bracteoliform processes densely clothed with long white hairs. Outer 2 tepals of fertile flowers linear-oblong, c. 6–7 mm. long, green centrally with 3 distinct ribs (the midrib distinctly excurrent in a fine, yellowish arista) broadly hyaline-margined, furnished with long, whitish multicellular hairs; inner 3 tepals similar but c. 1 mm. shorter, more narrowly hyaline-margined and somewhat widened at the base. Ovary c. 2 mm. long, obpyriform, delicate below with a flat, firm apex; style slender, c. 1.5 7–2 mm. long. Stamens c. 3.5–4.5 mm. long; filaments slender, fused for c. one quarter of their length to the pseudostaminodes; pseudostaminodes c. 1.5 mm. long, flabellate, dentate with a fimbriate dorsal scale; anthers narrowly oblong, c. 1 mm. long. Branches of partial inflorescence and bases of bracteoles incrassate and lignescent in fruit, the whole forming a soft, silky-hairy, burr-like unit. Fruit compressed-ovoid, c. 3 mm. long, apex concave with a distinct raised rim; seed brown, smooth and shining, c. 2 mm. long, finely reticulate.
