Etymology -"Hyle" is the Greek for forest implying "forest cereus".Hylocereus is best known for producing exotic, large fruits, known as Dragon Fruit. While all species of the genus have varying edible fruits, that of H. undatus is the primary species found in grocery stores and street markets - particularly in Asia. These fruits are slightly larger than an orange, with red skin accented by green scales.
Nearly 20 species of Hylocereus are recognized by most and they can be found naturally occurring from Southern Mexico down throughout Central America and into Northern South America. As the name implies, these plants grow primarily in the forested areas of this distribution. Those species grown for their fruits are grown on farms in other parts of the world, especially tropical Asia.
The species in this genus grow like vines, sprawling and clambering their way up into the trees. Most species are not epiphytic, but root in the ground and climb from there. The plants may branch frequently and grow quite high up exceeding 30 feet (10 meters) thus becoming quite massive. The stems are typically three-angled with wavy or punctuated margins and few short spines if any. Flowers of Hylocereus are the largest in the cactus family with the largest easily exceeding 12 inches (30cm) in length and diameter. The floral tubes are thick with leafy scales and no spines or bristles or hairs. The flowers are primarily white and fragrant opening at night. Surprisingly, these massive flowers will only remain open for only a few hours on just one night. This combination of large size and short lifespan make viewing a Hylocereus flower a real treat! Although, well-established plants in warmer climates may produce many flowers over the course of several nights.
While these plants are not often grown in pots and greenhouses due to their cumbersome size, the fast growth makes these popular for use in grafting. The extremely popular bright red Gymnocalycium cultivars sold as "Lollipop" cactus are almost always grafted onto a short section of Hylocereus. These do not last long as they prefer tropical growing conditions and are very sensitive to cold which most people don't realize.