L., Mant. Pl. Altera 294. 1771
Mastranzo de monte
Functionally monoecious shrub, 1-2.5 (6) m tall, densely hispidulous to scabrous, the trichomes coarse and erect; stems often mottled with purple. Leaves opposite, asperous; petioles 5-20 mm long; blades ovate-oblong, acute at apex, obtuse to rounded at base, 5-17 cm long, 2.5-8 (10) cm. wide, scabrous above, ± pilose below, crenate-serrulate; reticulate veins prominently raised. Inflorescences terminal corymbs; heads often secund, sessile, 4-7 mm long; phyllaries 8 or 9, obovate, 3-5 mm. long, 2-4.8 mm wide, acute or acuminate, closely imbricate, ciliate; flowers white; ray flowers 3-5, functionally pistillate, lacking stamens, the corolla 3- or 4-lobed, 2-2.7 mm long, the style divided nearly to base, exserted at anthesis while the head appears immature and the disk flowers are still closed; disk flowers 11-14, functionally staminate, the corolla 2.5-3.3 mm long, broadened above, densely pubescent especially on lobes, the anthers syngenesious, the ovary sterile, the style simple, protruding from corolla with anthers. Achenes thick, rounded-obovoid , 2-edged, glabrous except for densely villous apex, black, to 3 mm long; pappus lacking. Croat 6238, 12584.
Occasional, on the shore, particularly on the northern edge of the island. Flowers and fruits principally in the rainy season (May to December), but occasionally throughout the rest of the year.
Easily distinguished by the seemingly rayless white heads and by the black phyllaries at maturity. Stuessy (1975) reported Croat 12718 as a collection that intergrades with C. asperum and suggested that the two taxa may hybridize.
Though the style of the pistillate flower may still be present when staminate flowers open, the pistillate flowers usually have been pollinated and the achene has begun to enlarge. The plants are visited by a variety of insects, including butterflies, small bees, and wasps.
Achenes lack a pappus for dispersal, but the phyllaries become black at maturity. Birds may remove the entire, few-seeded head.
Costa Rica south to Peru, Bolivia, and Brazil; West Indies. In Panama, ecologically variable; known from tropical moist forest in the Canal Zone, Colon, Chiriqui, Veraguas, Herrera, Coclé, Panama, and Darién, from tropical dry forest in Coclé and Herrera, from premontane moist forest in the Canal Zone and Panama, and from premontane wet forest in Chiriqui, Veraguas, Coclé and Panama.