Leptocereus grantianus (sebucan) is a sprawling or suberect, nearly spineless cactus, reaching up to 2 meters in height and 3 to 5 centimeters in diameter. Its elongated stems have from three to five prominent ribs with broadly scalloped edges. Ribs of young joints are thin, and the small areoles or spine-bearing areas may bear from one to three minute, nearly black spines which disappear as the joints grow older. The flowers are solitary at terminal areoles, from 3 to 6 centimeters long, and nocturnal. The outer perianth segments are linear, green, and tipped by an areole like those of the tube and ovary. The inner perianth segments are numerous, cream-colored, oblong-obvate, obtuse, and about 8 millimeters long. The fruit is subglobose to ellipsoid and about 4 centimeters in diameter.