Description from Flora of China
Pycnanthemum elongatum Blanco.
Herbs erect, annual. Stems 1-1.5 m, angles scabrid. Petiole 0.3-2.2 cm, scabrid; leaf blade lanceolate to ovate-lanceolate, 2.5-7.5 × 1-2.5 cm, adaxially olive green, tuberculate hairy, abaxially glandular, minutely hispid on veins, base cuneate, margin serrulate, apex acute to acuminate. Spikes continuous, cylindric, terminal or axillary, 1.6-6.5 × 1-1.3 cm; verticillasters many flowered; bracts subulate, as long as calyx; fruiting calyx tubular dilated, ca. 7 × 3 mm, minutely hispid, transparently glandular; veins 10, prominent, arcuate transverse; teeth subulate, ca. 2 mm. Nutlets brown, oblong, ca. 1 × 0.6 mm, adaxially ribbed.
Taiwan [Indonesia, Philippines; South America].