Disocactus crenatus

Disocactus crenatus, the crenate orchid cactus, is a species of cactus and one of the most important parents in creating the epiphyllum hybrids commonly cultivated throughout the world. It is cultivated for its large white flowers.

Disocactus crenatus
Flower
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Cactoideae
Tribe: Hylocereeae
Genus: Disocactus
Species:
D. crenatus
Binomial name
Disocactus crenatus
(Lindl.) M.Á.Cruz & S.Arias
Synonyms[1]
Of Disocactus crenatus
  • Cereus crenatus Lindl.
  • Epiphyllum cooperi Clover
  • Epiphyllum crenatum (Lindl.) G.Don
  • Phyllocactus caulorhizus Lem.
  • Phyllocactus crenatus (Lindl.) Lem.
Of Disocactus crenatus subsp. kimnachii
  • ×Epinicereus cooperi (Regel) P.V.Heath
  • Epiphyllum crenatum subsp. kimnachii (Bavo) U.Guzmán
  • Phyllocactus belgica Laet-Contich
  • Phyllocactus cooperi Regel
  • Phyllocactus hildmannii Hildm.
  • Phyllocactus pfersdorffii Rümpler
  • ×Rowleyara hildmannii (Hildm.) P.V.Heath
  • ×Seleniphyllum cooperi (Regel) G.D.Rowley

Description

D. crenatus subsp. crenatus

The stem is erect to ascending, profusely branched, primary stems terete (tapering at both ends) or 3-angled for a short portion at base, becoming ligneous (woody), flat at most of their length, secondary stems flat, flattened portions to 60 cm long, to 6–10 cm wide, stiff and rather succulent. The leaves are lanceolate to long linear, acute or obtuse, median nerve rather thick, margins deeply or coarsely crenate, lobes oblique; areoles at the bases of stems sometimes bearing hairs or small bristles, internodes (plant stem part between nodes) narrow or broad. The Epidermis is green or almost grayish green, smooth.

The flowers are up to 18–29 cm long and (10-)15–20 cm wide, nocturnal, but remaining open for several days, fragrant. The outer tepals are inserted within 2 cm of receptacle apex, (7-)10–12 cm long, broadly oblanceolate-linear, greenish yellow to tawny yellow or reddish amber, the outermost sometimes margined red or streaked; inner tepals as long as outer, spathulate to oblanceolate, acuminate to mucronate, white, creamy white or greenish yellow. The Pericarpel (hypanthium) is 5-angled, 3 cm long, 1,5-1,7 cm thick, with acute, long-decurrent podaria, bracteoles (small bracts) subtening 0-2 (-8) spines to 7 mm long, green. The receptacle is 10–12 cm long, about 1,5 cm thick at middle, green often reddish at apex or reddish throughout, bearing numerous linear to oblong, obtuse, ± keeled bracleoles 2–3 cm long, ± spreading. The nectaries are about 3–4 cm long, stamens numerous, declinate,[2] shorter than the tepals, inserted in two zones the lower one ca 4 cm long, from a point ca 4 cm from the ovary chamber, the upper zone forming a throat circle ca 2 cm above, filaments 5–7 cm long, pale yellow or pale greenish yellow; style 15–20 cm long, as long or longer than stamens, 2–3 mm thick, widest at base. The stigma lobes are white, 8-9, papillose (nipple-like). The fruit is oblong to globose (globe-shaped), the podaria long decurrent, acute.

D. crenatus subsp. kimnachii

This subspecies differs from the typical variety by: stems 4–6 cm wide, lobes usually semicircular; pericarpel and receptacle subterete (tapering at the bottom) in cross-section; pericarpel with subconical (somewhat cone shaped at the bottom) or obtuse, shortly decurrent podaria and with bracteoles subtending ca 6 (0-20) spines to 12 mm long; outer tepals usually inserted within 4–8 cm of tube apex; fruit globose, the podaria shortly decurrent, obtuse.

Taxonomy

The epithet crenatus means with crenations (wavy-toothed) and refers to the crenated stem margins. The subspecies epithet kimnachii honours Myron Kimnach (1922-2018), a botanist mainly working with epiphytic cacti and Crassulaceae, and for many years working at the University of California, Berkeley and Huntington Gardens. Kimnach was director of the Huntington Botanical Gardens for 25 years and editor of the Cactus and Succulent Society of America's Journal, and Managing Editor of its peer-reviewed, technical yearbook, Haseltonia for ten years.[3]

This species is very distinct. The flowers of Epiphyllum grandilobum are similar but the stem morphology is very different. Relationships and generic limits in the tribe Hylocereeae have long been unclear. A molecular phylogenetic study in 2016 showed that this species, which was then placed in the genus Epiphyllum was firmly nested within Disocactus.[4]

Distribution and habitat

From Mexico (Oaxaca & Chiapas) to Honduras. Epiphytic (grows upon another plant) or lithophytic (grows on rocks) in moist or wet forests, sometimes in oak forests. 1.750 m alt. or less.

Cultivation

This species was shown at an exhibition at the Royal Horticultural Society's Garden in 1844 and won highest medal for a new introduction. It had been collected in Honduras five years earlier by Georges Ule Skinner and sent to Sir Charles Lemon who flowered it for the first time in 1843. Lindley thought it to have originated in the island of Antigua. D. crenatus is the only species of Disocactus that has been used in hybridization to any extent. Most of the colored hybrids have mainly Disocactus genes and are perhaps better referred to as Disocactus hybrids rather than epiphyllum hybrids.

It is an easily cultivated, fast growing epiphyte. Needs compost containing plenty of humus and sufficient moisture in summer. Should not be kept under 12 °C (53,5 °F) in winter. Can be grown in semi-shade or full sun. Extra light in the early spring will stimulate budding. Flowers in late spring or early summer.

The cultivar 'Cooperi' resembles D. crenatus subsp. kimnachii, differing only in having the outer petals at the apex of the tube. It was originally reported that 'Cooperi' was a hybrid involving Selenicereus, and Clive Innes stated that he "re-made" the cross between D. crenatus and Selenicereus grandiflorus, obtaining several plants identical with 'Cooperi'. However, it was shown in 1997 that this was not correct, DNA analysis showing no evidence of Selenicereus.[5]

References
  1. "Disocactus crenatus (Lindl.) M.Á.Cruz & S.Arias". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2020-05-16.
  2. Declinate: descending in a curve or drooping, Collins English Dictionary – Complete and Unabridged. S.v. "declinate." Retrieved 2011-05-09 from The Free Dictionary
  3. Cactus and Succulent Society of America, 2007 Convention Speakers, Cactus Lectures, Myron Kimnach.
  4. Cruz, Miguel Ángel; Arias, Salvador & Terrazas, Teresa (2016), "Molecular phylogeny and taxonomy of the genus Disocactus (Cactaceae), based on the DNA sequences of six chloroplast markers", Willdenowia, 46 (1): 145–164, doi:10.3372/wi.46.46112
  5. Metz, Fröhlich, Kimnach & Meyerowitz (1997), article in Haseltonia.
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