Disocactus
Disocactus is a genus of epiphytic cacti native to Mexico and Central America, distinguished by flattened, leaf-like or slender cylindrical stems and showy, day-blooming flowers in shades of red, pink, orange and magenta. The genus includes the well-loved rat-tail cactus and a number of species that have been crossed extensively to produce the big-flowered "orchid cactus" hybrids of the houseplant trade.
Unlike the desert cacti most people picture, Disocactus species grow perched on tree branches and mossy rocks in humid forest, trailing or arching rather than standing upright. Because their flowers open by day and are often brightly coloured, they are among the most rewarding epiphytic cacti for a bright windowsill or a sheltered hanging basket.
Description
Members of Disocactus are shrubby or pendent epiphytes with jointed stems that arise from a woody base. The stems take two broad forms: some species have flat, strap-shaped stems with a prominent midrib and scalloped or toothed margins, looking much like thick green leaves; others (notably the rat-tail cactus) have slender, rope-like cylindrical stems clothed in fine bristly spines. New growth typically hangs or sprawls, which is why so many are grown in baskets.
The flowers are the main event. They emerge from areoles along the stem margins and open during the day, usually funnel- to bell-shaped and lasting several days. Colours run from scarlet and orange through rose-pink to magenta, and the blooms are far less strongly scented than those of the night-flowering epiphytes. Small, berry-like fruit follow successful pollination.
Distribution
The genus is centred on Mexico and extends through Central America, growing as an epiphyte (and sometimes a lithophyte) in seasonally moist tropical and subtropical forest. Plants root in pockets of leaf litter and moss on tree limbs, where they receive dappled light, good air movement and regular humidity — conditions worth keeping in mind when growing them at home.
Notable species
- Disocactus flagelliformis — the rat-tail cactus, with long trailing bristly stems and vivid pinkish-red flowers; the most widely grown species and a classic hanging-basket plant. Formerly placed in Aporocactus.
- Disocactus ackermannii — flat-stemmed with large, brilliant red flowers; an important parent of many epiphytic-cactus hybrids.
- Disocactus phyllanthoides — flat, leaf-like stems and soft pink day-flowers; long cultivated and once known under Nopalxochia.
- Disocactus macranthus — slender-stemmed with fragrant, pale flowers.
- Disocactus speciosus — showy, richly coloured red blooms; formerly placed in Heliocereus.
Cultivation
Disocactus species are grown much like other forest cacti rather than like desert species. Give them bright, filtered light — enough to encourage flowering, but with protection from harsh midday sun that can scorch the stems. A humus-rich but open, free-draining medium suits them; many growers use an epiphyte-oriented mix with added bark and grit rather than a purely mineral one.
Water regularly through the warm growing season, letting the top of the mix dry slightly between waterings, and reduce watering in winter to encourage a cool, drier rest — this rest period helps trigger the spring flush of flowers. They appreciate more humidity and more frequent feeding than desert cacti, but still resent waterlogging, so drainage remains essential. See Watering and Repotting for general technique. Most are happy in a hanging basket where the stems can cascade freely.
Hybrids and hobby notes
Disocactus has been central to the breeding of large-flowered epiphytic cacti. Crosses within the genus and with related epiphytes (such as Epiphyllum and Selenicereus) have produced the huge, colourful day-blooming hybrids sold generically as "orchid cacti." When buying, be aware that older references may still file these plants under the former genera Nopalxochia or Aporocactus, both now folded into Disocactus.
For the home grower these are forgiving, fast-growing plants that reward a little humidity and a winter rest with generous flowering. They are easily increased from cuttings, making them popular pass-along plants among collectors.
Propagation
Stem cuttings are the usual method: a length of stem is cut, allowed to callus for a few days, then rooted in a barely-moist, open mix — see Propagation — cuttings. Species and named forms are almost always propagated this way to stay true to type. Seed is also possible for species and for breeding new hybrids, though seedlings take longer to reach flowering size; see Propagation — seed.
See also
- Epiphyllum — the closely allied orchid cacti
- Selenicereus · Soil and potting mix · Watering · Repotting
- Propagation — cuttings · Propagation — seed · Pests and diseases