Synonymy
Cactus phyllanthoides De Candolle (1813) Cat. Hort. Monsp. 84
Cactus speciosus Bonpland (1813) Descr. Pl. Rar. Malm. 8 non Cavanilles 1803
Epiphyllum speciosum (Bonpland) Cavanilles (1819) Suppl. Pl. Succ. 84
Cactus elegans Link (1822) Enom. 2:25
Epiphyllum phyllanthoides (de Candolle) Sweet (1826) Hort. Brit. 172
Cereus phyllanthoides (de Candolle) de Candolle (1828) Prodr. 3:469
Phyllocactus phyllanthoides (de Candolle) Link (1831) Handb. Gewächs. 2:11
Opuntia speciosa (Bonpland) Steudel (1841) Nom. ed. 2, 2:222
Disocactus phyllanthoides (de Candolle) W. Barthlott 81991) Bradleya 9:88

'Deutche Kaiserin'
'Empress'
'German Empress'
'Giant Empress'

Ethymology
Phyllanthoides (lat.) = similar to phyllanthus. This species was among the first flat stemed species to be described and the name recalls that it is similar to the first descripted flat stemed cacti; Cactus phyllanthus, today Epiphyllum phyllanthus. Some authors states that this plant first flowered in the garden of La Malmaison, belonging to the late Empress Jesephine. Which could expain some of the popular names as German Empress, Deutche Kaiserin, Giant Empress, Drottningkaktus (Swedish for Queen's Cactus) except for the wrong country. This story could be a myth.

This cacti was called Nopalxochitl by the Aztecs with explains the former generic name Nopalxochia.

History
As with so many of the early descripted cacti the history is somewhat unclear. Sims and Edwards states that it was discovered by the celebrated travellers Humbolt and Bonpland in April 1801, near the small village of Turbaco, near Carthagena. Reported by Bonpland to have first flowered at La Malmaison and at the Botanical Garden of Montpellier, France.
However, this species was illustrated much earlier. Both Hernández (1651) and Plukenet (1691) figured the species and it has probably been in cultivation since prehistoric times.

Origin and habitat
Said to have come from Colombia, but most likely it originated in S Mexico. Known for certainity only from cultivation.

Systematics
A distinct species related to D. ackermannii. It has previously been placed in Nopalxochia, but not much support a generic status for that taxon. This species, as well as other of the former Nopalxochia species show affinity to Webereocereus which certainly make the systematics of this group even more complex.

Cultivation
 D. phyllanthoides is very easily cultivated. The soil should contain plenty of leaf-mould and the plant be given regular water and dozes of fertilizer in summer. Best kept relatively cool and dry in winter, 10º-15C (50-59ºF). Plants held under proper conditions can produce flowers at least three timeas a year, but main flowering period is spring.

Description
Stems to 1 m long or more, branching, primary stems to 40 cm long, 6 mm thick, woody and terete at base, flattened at apex; secondary stems flat, lanceolate, acute, margins coarsely crenated or scalloped, obtusely toothed, with terete, stalk-like base, 15-30 cm long, 2,5-5 cm wide; areoles nude except for young growth; epidermis green or reddish, nearly smooth.
Flowers campanulate, funnel-shaped, diurnal and scentless*, 8-10 cm long, 7-9 cm wide, produced on year old branches; pericarpel ovate with a few spreading bracteoles; entire receptacle 2,5-5 cm long, 7-10 mm thick; tepals, bracteoles more numerous than on the pericarpel, reflexed, green to blackish purple, naked in their axills; outer tepals lanceolate, opening irregulary before flowering, then spreading widely, rose-pink; inner tepals lanceolate-obtuse, more or less erect, pink, paler inside; stamens declinate, as long as the tepals, white; style as long as tepals white, stigma lobes 5-7.
Fruit ellipsoid, 3-4 cm with low ribs, green at first, later red. Seeds dark brown.

* J. Borg (1951) report it as "sweet-scented".