AFRICAN

ORCHIDS

Erasanthe P.J.Cribb, Hermans & D.L.Roberts, Adansonia, III, 29: 28 (2007).
Description:
Erasanthe P.J. Cribb, Hermans & D.L. Roberts is a monospecific genus comprising the species Erasanthe henrici and its two subspecies, the typical subsp. henrici and the restricted subsp. isaloensis H.Perrier ex P.J.Cribb, Hermans & D.L.Roberts (Cribb et al., 2007). The species differs morphologically from typical members of Aeranthes in having stout rather than fibrous roots and large white flowers rather than small, fairly translucent flowers. The flowers also have distinctive lacerations along the edge of the lip, which can vary across populations and subspecies. The nectar spur is typically 5-6 inches (12-16 cm) long, more than three times the length of most nectar spurs in Aeranthes. A recent molecular study by Claire Micheneau and colleagues (2008) corroborated the morphological evidence for the new genus. The genus Aeranthes appears to be generally monophyletic, meaning that it forms a distinct group, with Aeranthes henrici as a major outlier.
Etymology:
The generic name Erasanthe is derived from an anagram of Aeranthes
Type species:
Aeranthes henrici Schltr.
Habitat:
The genus is endemic to Madagascar with the typical subspecies growing in the north and northeast region of the country in diminishing patches of humid forest between 2,600 and 3,280 feet (800 and 1,000 m) (Cribb et al., 2007). Plants generally grow on tree trunks less than 13 feet (4 m) from the ground, often following small waterways, and no host specificity has been demonstrated (K. Theiss, pers. obs.). Plants have been found growing on everything from tree ferns to Pandanus. The more restricted subspecies is found much farther south in canyons in Isalo National Park as well as in the transitional forest of Zombitse-Vohibaisia National Park.
In its native habitat, plants of Erasanthe henrici flower in March and April, releasing their seeds in late October/early November (K. Theiss and J.J.R. Randrianarimalala, pers. obs.). Plants typically produce one to eight flowers per inflorescence, with individual blossoms persisting for up to two weeks without pollination. The flowers produce scent in the late afternoon to early evening and are presumably pollinated by hawk moths.
Cultivation:
Erasanthe henrici is difficult to flower in cultivation, which may increase the demand for plants. High levels of light will cause the leaves to yellow and may overdry the plants.
Notes:
Schlecter placed the species in the genus Aeranthes Lindl. where it remained until 2007, when researchers from the Royal Botanic Gardens, Kew, erected a new genus Erasanthe based on morphological and molecular evidence.
Distribution:
Madagascar.
Species:

Erasanthe henrici (Schltr.) P.J.Cribb, Hermans & D.L.Roberts N. & NW. Madagascar.
Erasanthe henrici subsp. henrici. N. & NW. Madagascar.
Erasanthe henrici subsp. isaloensis P.J.Cribb, Hermans & D.L.Roberts Madagascar.

Bibliography and References:
Schlechter, R. 1925. Orchidaceae Perrieranae.Fedde, Repertorium Specierum Novarum Regni Vegetabilium 33:1-391; Carlsward B. S., Whitten W. M., Williams N. H. & Bytebier B. 2006. Molecular phylogenetics of Vandeae (Orchidaceae) and the evolution of leafl essness. American Journal of Botany 93: 770-786; Cribb PJ, Hermans J, Roberts DL. 2007 Erasanthe (Orchidaceae, Epidendroideae, Vandeae, Aerangidinae), a new endemic orchid genus from Madagascar. Adansonia 29. (1): 27-30; Perrier De La Bâthie H. 1939. Orchidaceae 1. Flore de Madagascar 49 (1). Imprimerie offic ielle, Tananarive, 477 p., 41 pls; Perrier De La Bâthie H. 1941. Orchidaceae 2. Flore de Madagascar 49 (2). Imprimerie officielle, Tananarive, 387 p., 36 pls; Stewart J. 1978. A new species of Aeranthes from Rhodesia – a genus new to Africa. American Orchid Society Bulletin 47 (8): 719-723; Williamson g. 1990. New orchids from the Flora Zambesiaca region. Kirkia 13 (2): 245-252; References: WCSP (2017). 'World Checklist of Selected Plant Families. 27.02-2017; http://apps.kew.org/wcsp/