Angraecum eburneum subsp. xerophilum

Names and Taxonomy

The accepted scientific name for this taxon is Angraecum eburneum subsp. xerophilum H.Perrier.^[1] It was first published in Notul. Syst. (Paris) 7: 133 (1938). Kew’s Plants of the World Online lists the subspecies as accepted and records its native range as south‑west Madagascar.^[1] No synonymy for the subspecies is documented in the consulted sources.

How to Identify This Species

Angraecum eburneum subsp. xerophilum is a lithophytic subshrub that grows on rock outcrops. Like other members of the genus, it bears linear leaves arranged in two ranks along a monopodial stem, though specific leaf measurements are not documented.

The flowers are notably smaller than those of the type subspecies. Sepals and petals reach a maximum length of about 3 cm.^[2] The labellum is transverse, unusually wide (≈35 mm) compared with its length (≈20 mm without the apex). The nectar spur is relatively long, measuring 7–8 cm.^[2] Flowers are white, emit a pleasant nocturnal fragrance, and are borne on short racemes. These traits together help separate the taxon from the more robust subsp. superbum and from the typical subsp. eburneum.

Native Range and Habitat

The subspecies is endemic to the south‑west region of Madagascar. Herbarium records place the type locality at “Sud‑Ouest d’Ambovombe, Kotoala” (MNHN specimen, 1932).^[3] In the wild it grows lithophytically on rocky substrates within a seasonally dry tropical biome. Elevational limits are not documented.

Species‑Specific Care

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Because the species is naturally adapted to very well‑drained rocky habitats, the key cultural requirement is to prevent the root zone from staying wet for extended periods. A gritty substrate (e.g., a blend of bark, charcoal, perlite, and coarse sand) mimics its lithophytic niche and helps avoid rot. The plant’s modest size makes it suitable for modest‑sized pots, which also aids in maintaining the dry conditions it prefers.

Flowering and Pollination

In cultivation under northern‑hemisphere conditions the subspecies has been reported to flower in mid‑summer (July–August).^[2] Flowers are long‑lasting and emit a noticeable fragrance at night, a trait typical of Angraecum species that are pollinated by nocturnal hawk moths. However, a specific pollinator for subsp. xerophilum has not been documented in the available literature.

Evidence and Limitations

The profile draws on three primary sources: Kew’s taxonomic database for name status and distribution, a horticultural description from African Orchids, and a herbarium specimen record confirming the south‑west Madagascar type locality. Important gaps remain, notably precise temperature requirements, detailed leaf morphology, elevation range, and confirmed pollinator identity. Future field observations and controlled cultivation trials would be needed to fill these gaps.