Shrubs, epiphytic, hemi-epiphytic, or epipetric, straggling, climbing, scandent, or pendent, irregularly many branched. Roots diffuse, often adventitious along stem internodes. Stems segmented, green, blue-green, gray-green, or somewhat whitish with wax; segments elongate, 3-winged or -angled, length highly variable, 10-500+ × [1-]4-7.5[-10] cm, distinctly narrowed proximally, glabrous; ribs (2-)3(-5), winglike to narrowly triangular in cross section, rib crests straight to undulate, crenate [toothed, notched, or lobed], often with a line of hard, brown to gray bark between areoles; areoles (10-)35-50 mm apart along ribs, oval, short woolly, sometimes subtended by minute, vestigial leaves at growing stem tip; areolar glands inconspicuous; cortex and pith mucilaginous. Spines 0-4[-8] per areole, whitish or yellowish to brownish [blackish or red, aging gray], acicular [awl-shaped or hairlike], straight, terete, generally short, 0-4[-10] mm, hard, bases sometimes conic or swollen, smooth, glabrous; radial and central spines not distinguishable. Flowers nocturnal, lateral to subterminal on 1+-year-old stems, at adaxial edges of areoles, long tubed, funnelform, [3-]25-29[-38] × [8-]15-25[-30] cm; outermost tepals often greenish, yellow, pink, or occasionally purplish red or white, 10-15 × 1-1.5 cm, margins entire; inner tepals white to cream [rarely pinkish or red], 10-15 × 1.5-2.5 cm, margins entire; ovary tuberculate [to smooth], scaly, spineless, usually without hairs or wool; scales triangular, broad, thick conspicuous, to 25 mm; stigma lobes to 24, white. Fruits irregularly dehiscent along 1 side, red [to purple or magenta], oblong to ovoid or spheric, [20-]50-125 × 40-120 mm, fleshy, spineless; pulp white; scales persistent, green, triangular, conspicuous, thick and fleshy, to 4+ cm; floral remnant often persistent. Seeds black, [elongate or] pyriform [to reniform], 2-3 mm, glossy; testa smooth or minutely textured. x = 11.