The two arborescent species of this section are found in the barranca vegetation of the pine-oak forests or the evergreen cloud forests of the Sierra Madre Occidental in Mexico, from Durango to Oaxaca and through the Trans-Mexican Volcanic Belt to Puebla and Veracruz, south in Central America to Panama, at elevations from 800 to 3,000 meters. Their leaves are opposite or whorled in sets of three or four. The numerous flowers are held in terminal panicles, with floral tubes less than eight millimeters long, and have smooth to lobed nectaries The spreading to reflexed sepals are colored a lustrous reddish purple and the petals are lavender. The stamens occur in two unequal series with yellow pollen. The fruit contains between 50 and 100 seeds.