Cereus hexagonus or lady of the night cactus is a species of columnar cactus found in Ecuador and Venezuela.
Cereus hexagonus grows like a tree with erect shoots that branch out from near the base and can reach heights of growth of up to 15 metres. The cylindrical, segmented, glaucous light green shoots have a diameter of up to 12 centimeters and more. There are four to seven thin, wavy ribs that are 3 to 5 centimeters high. The areoles on it are small. The thorns are missing on young shoots or there are only a few. Older shoots have 8 to 10 or more unequal spines per areole. The initially brown thorns become lighter later. They are 5 to 6 centimeters long.
The white flowers are 20 to 25 centimeters long. The 5.5 to 13 centimeters long, egg-shaped fruits are light red. They contain white or pink flesh.
