Disocactus phyllanthoides
| Light | Bright, filtered light; protect from harsh direct midday sun |
|---|---|
| Water | Regular through the growing season; ease off in winter but never bone-dry for long |
| Soil | Open, humus-rich epiphytic mix that drains freely (see Soil and potting mix) |
| Temperature | Frost-free; keep above about 5 °C, USDA zones 10–11 |
| Propagation | Stem cuttings (primary); also seed |
| Toxicity | Non-toxic to cats and dogs |
Disocactus phyllanthoides is a flat-stemmed, trailing epiphytic cactus from the cloud forests of eastern Mexico, prized for its soft rose-pink, funnel-shaped flowers. Grown in European conservatories and windowsills for centuries, it is one of the oldest cultivated ornamental cacti and is still widely known by its old garden name German Empress (also pond lily cactus). It belongs to the epiphytic genus Disocactus and is an important parent in the history of hybrid "orchid cacti".
Description
Disocactus phyllanthoides is a spineless epiphyte with long, arching to pendent stems. The stems are flattened and strap-like, with gently scalloped (crenate) margins from which the flowers arise; young growth and the stalk-like stem bases are terete (rounded in cross-section) before the stem flattens out. Lacking the fierce spines of desert cacti, the plant relies on its clambering, cascading habit to drape over branches in the wild and over the rim of a pot in cultivation.
The flowers are the main attraction: slender, funnel-shaped blooms in soft shades of pink, carried along the notches of the stem margins in spring. They are diurnal — open by day rather than the fleeting night-bloomers of many cacti — and scentless, appearing in generous flushes on well-grown plants, giving the older cultivated forms their reputation as reliable, floriferous houseplants.
Distribution and habitat
The species is native to eastern Mexico, where it grows as an epiphyte in humid montane and cloud forest, perched on tree branches and occasionally on mossy rock. In these habitats it enjoys warm temperatures, high humidity, bright but dappled light beneath the canopy, and roots that are never left standing in water but are rarely fully parched. Its wild populations have declined with the clearing of these forests — largely for coffee plantations, small-scale farming and grazing — and the species is assessed as Vulnerable on the IUCN Red List. Understanding this epiphytic origin is the key to growing it well.
Cultivation
Unlike the terrestrial desert cacti, Disocactus phyllanthoides wants more moisture, more humidity and richer footing. Grow it in an open, humus-rich epiphytic mix — the sort used for jungle cacti and epiphytic orchids, with plenty of bark or coarse organic matter — in a pot or, better still, a hanging basket that shows off the trailing stems.
Give it bright, filtered light: enough to ripen the growth and encourage flowering, but with protection from scorching direct sun, which can yellow or burn the flat stems. Water regularly while the plant is in active growth, letting the surface dry between drinks, and reduce watering over winter to give a cooler, drier rest that helps set buds — though it should never be kept as arid as a desert species. A period of cooler, drier winter rest is one of the surest ways to earn a good spring display. Feed lightly during the growing season and see Watering and Repotting for general technique.
Propagation
The easiest method is stem cuttings. Take a healthy segment of flattened stem, allow the cut end to callus for a few days, then set it in a light, free-draining mix and keep it warm and lightly moist until roots form. Cuttings root readily and come true to the parent, which is how the old garden forms have been passed along for generations. The species can also be grown from seed, though this is slower and mainly of interest to hybridisers. See Propagation — seed for that route.
Cultivars and hybrids
D. phyllanthoides has a long horticultural pedigree. The plant grown for centuries as German Empress represents one of the earliest and most enduring cultivated forms. More importantly, the species has been used extensively in breeding the large-flowered hybrid "orchid cacti", where its genes contribute to countless crosses with related epiphytic genera. Many plants sold under the Disocactus and related epiphyllum-type hybrid names trace part of their ancestry to this species.
Common problems
- Rot — usually from a heavy, waterlogged mix or cold, wet winter conditions; stems soften and discolour. Use an open epiphytic medium and ease off water in the cold months.
- Failure to flower — most often from too little light or the lack of a cooler, drier winter rest; both are needed to set buds well.
- Scorch — harsh direct sun can bleach or brown the flat stems; provide bright but filtered light.
- Pests — mealybugs (white fluff in the stem notches) and scale are the usual offenders; see Pests and diseases.
See also
- Disocactus — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases