Body cylindrical, becoming large to over 5 m tall, branches erect. Ribs 6-8, rounded. Spines few or absent, yellowish brown. Flowers white. [Trichocereus pachanoi Britton & Rose]
Other cylindrical nocturnal species with flowers about 18 cm long opening at night and remaining open for the following day, keyed out above, include 3 species from Argentina: E. spachiana (Lem.) Friedrich & Rowley, E. schickendantzii (F.A.C. Weber) and E. terscheckii (Pfeiff.) Friedrich & Rowley while E. chiloensis (Colla) Friedrich & Rowley from Chile has smaller flowers about 10 cm long that remain open for several days.
Source: (1997). Cactaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.