Selenicereus undatus

Natural range and habitat of Selenicereus undatus

Selenicereus undatus occurs naturally from Mexico to Honduras, where it grows on trees as an epiphytic cactus in seasonally dry tropical habitat. The older name Hylocereus undatus is still widely used for the species.

It is now widely cultivated in warm regions for dragon fruit.

How to care for Selenicereus undatus

• Light: Give very bright light and direct sun, increasing sun exposure gradually.
• Temperature and humidity: Keep it around 18–30 °C. Protect it from prolonged temperatures below 15 °C. Average household humidity, around 40–50%, is suitable.
• Water: While the stems are growing, water thoroughly, then let most of the potting mix dry before watering again. Water less often when growth slows.
• Potting mix and feeding: Use a loose, free-draining cactus mix with organic material and coarse grit. Feed while new stems are developing.
• Support: Use a strong post or trellis that can carry a heavy mature crown. Guide young stems upward and give the top growth room to branch and hang.
• Flowering and propagation: Stem cuttings produce new plants with the same characteristics. For indoor fruiting, transfer pollen by hand while the flowers are open at night. Some clones can set fruit with their own pollen, but compatibility varies. Pollen from another compatible dragon-fruit plant can improve the chance of fruit developing and may produce larger fruit.
• Repotting: Increase pot size modestly when the root system becomes crowded. If the potting mix compacts and no longer drains freely while the roots still fit, replace the mix in a container that still fits the root ball.

Problems to watch for with Selenicereus undatus

• The stem base turns yellow, translucent or soft: Excess moisture has led to root or stem rot. Cut affected tissue back to healthy tissue with a clean tool, discard the rot and reroot healthy sections in fresh potting mix that drains well.
• Dry tan lesions enlarge or turn black: A stem disease called canker may be developing. Isolate the plant, cut affected stem sections back to healthy tissue with a clean tool and disinfect the tool between cuts. Use a treatment only when its label covers the disease and the plant's intended use: edible dragon fruit if the fruit may be eaten, or ornamental cacti if the plant is grown only as an ornamental.
• Cottony insects, scale, thrips or feeding damage appear: Identify the pest first. Choose a treatment labelled for that pest and the plant's intended use, then follow the label for repeat applications.
• Stems become thin and weak: The plant needs stronger light or firmer support. Increase light slowly and secure new growth to a sturdy trellis.
• Flowers open and no fruit follows: Pollination may have been incomplete. Hand-pollinate fresh night-opening flowers and use pollen from another compatible dragon-fruit plant when available.

Selenicereus undatus has sharp parts

• This plant is non-toxic to cats and dogs. Its effects on people are unclear.
• Sharp spines can puncture the mouth, eyes, skin or paws.
• Handle it carefully. Contact a veterinarian or medical professional after a serious injury, especially to the eye.

Why is it called Selenicereus undatus?

Selenicereus combines Selene, the Greek moon goddess, with Cereus, a cactus name associated with a wax taper or candle. The epithet undatus is Latin for wavy or undulating and describes the rippled stem margins.

Nathaniel Lord Britton and Joseph Nelson Rose established the genus Selenicereus in 1909 in Contributions from the United States National Herbarium, volume 12, page 429.

Adrian Hardy Haworth first described it as Cereus undatus in 1830 in Philosophical Magazine and Annals of Philosophy, new series, volume 7, page 110. David Richard Hunt later placed it in Selenicereus as Selenicereus undatus in 2017 in Cactaceae Systematics Initiatives, volume 36, page 35.