Selenicereus undatus
| Light | Bright light to full sun once established; some afternoon shade in the hottest climates |
|---|---|
| Water | Regular through the warm growing season, letting the mix dry a little between; much drier and cooler in winter |
| Soil | Rich but free-draining mix with plenty of organic matter (see Soil and potting mix) |
| Temperature | Frost-tender; happiest above about 10 °C, USDA zones 10–11 |
| Propagation | Cuttings (easy and standard); also seed |
| Toxicity | Non-toxic; the fruit is a widely eaten food crop |
Selenicereus undatus is the common white-fleshed dragon fruit or pitaya, a vigorous, triangular-stemmed climbing cactus grown commercially across the tropics for its large, colourful fruit. A member of the genus Selenicereus, it is an epiphytic and lithophytic vine that clambers over trees, rocks and trellises using aerial roots, producing spectacular night-blooming flowers followed by the familiar pink-skinned, black-speckled fruit sold in markets worldwide.
Description
Selenicereus undatus is a sprawling, climbing or scrambling cactus with fleshy, three-sided (triangular) green stems that can reach many metres in length. The stem margins are wavy — the source of the old species name undatus, meaning "wavy" — and bear small areoles with only very short, inconspicuous spines. Along the stems the plant throws out abundant aerial roots that anchor it to supports and let it climb high into trees or over walls.
The flowers are among the largest and most dramatic in the cactus family: creamy white, funnel-shaped and often 25–30 cm long, opening for a single night and heavily fragrant. They give the plant one of its shared common names, "queen of the night," used across several night-blooming climbing cacti. Successful pollination is followed by the well-known fruit — an oval berry with bright pink to red skin bearing leafy green scales, and sweet, mild white flesh dotted with tiny edible black seeds.
Distribution and habitat
The exact wild origin of S. undatus is uncertain, as it has been cultivated and spread by people for so long, but it is generally attributed to Mexico and Central America. It grows as an epiphyte and lithophyte in seasonally dry tropical forest, scrambling over host trees and rocky outcrops.
Through cultivation it has become pantropical, and in many frost-free regions — parts of Southeast Asia, Australia, the Caribbean and elsewhere — it has naturalised readily from discarded cuttings, since even a fallen stem segment will root and grow.
Cultivation
Dragon fruit is one of the more forgiving cacti to grow, provided it has warmth and support. Unlike most desert cacti it appreciates a richer, more moisture-retentive mix than a pure mineral one, and more frequent water through the warm months — though it still resents standing wet, so drainage remains essential. Give it bright light to full sun for good flowering and fruiting, with a little shade from scorching afternoon sun in the hottest climates to prevent stem burn.
Because it is a climber, it needs a sturdy trellis, post or frame to scramble up; commercial growers train it over posts topped with a supporting frame so the stems cascade down. It is decidedly frost-tender and should be protected from cold and kept drier and cooler over winter. See Watering and Repotting for general technique.
Many named fruiting varieties are self-sterile or set fruit poorly on their own, so hand-pollination, or growing more than one clone together, can greatly improve yields. Because the flowers open only at night, hand-pollinating after dusk is a common practice among home growers.
Propagation
Propagation from stem cuttings is easy and by far the most common method, and is how named fruiting cultivars are maintained true to type. A length of stem is cut, allowed to callus for several days, then set in a free-draining mix, where it roots quickly in warm conditions. Cutting-grown plants also reach flowering and fruiting size far sooner than seedlings.
The plant can also be raised from seed scooped from ripe fruit, which germinates readily and is fun to try, but seedlings are slow to reach fruiting size and will vary from the parent.
Cultivars
A great many fruiting selections exist, chosen for fruit size, skin colour, sweetness and self-fertility. The species itself is the classic pink-skinned, white-fleshed type; note that the deep red- and magenta-fleshed dragon fruits usually belong to related species and hybrids within Selenicereus rather than to S. undatus itself.
Common problems
- Rot — soft, browning stems from overwatering, poor drainage or cold, damp winters; the most frequent cause of loss.
- Poor fruit set — often down to self-sterility or a lack of pollinators; hand-pollination or a second clone usually fixes it.
- Sunburn — sudden exposure to intense sun can scorch and scar the stems; acclimatise plants gradually.
- Pests — mealybugs, scale and, in the open, ants and fruit-piercing insects; see Pests and diseases.
See also
- Selenicereus — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases