Angraecum Species: Names, Identification, and a Searchable Index

1. Overview of the genus Angraecum

Angraecum Bory was first described in 1804 and is now recognised as the largest genus of the subtribe Angraecinae (Orchidaceae) [1]. The genus ranges from tropical West & Central Africa across the Indian Ocean islands to Sri Lanka, with a strong centre of diversity in Madagascar where roughly 140 species are endemic [9]. Current estimates of accepted species differ slightly among authorities: Kew lists over 200 names, Wikipedia cites ~220 species, and the most recent doctoral revision records 179 species (179 species, 3 subspecies, 5 varieties) [11]. All counts reflect the fluid nature of orchid taxonomy, where new molecular studies frequently synonymise or resurrect names.

2. Nomenclature basics for Angraecum

Each scientific name consists of the genus name Angraecum followed by a specific epithet and the author citation (e.g., Angraecum sesquipedale Thouars). The author indicates who first validly published the name; the original publication is recorded in the International Plant Names Index (IPNI) and reproduced on Kew’s portal [1]. A *type species* anchors the genus name – the type for Angraecum is Angraecum eburneum Bory [1].

Synonyms arise when the same taxon is described under different names. Kew’s database lists both homotypic (nomenclatural) and heterotypic (taxonomic) synonyms; for example, Angraecum sesquipedale has four homotypic synonyms such as Aeranthes sesquipedalis (Lindl.) [3]. When consulting labels or trade lists, growers should verify the accepted name through a current checklist (e.g., Kew’s PO​W) to avoid confusion with horticultural synonyms.

3. Taxonomic structure – sections and infrasections

Historically, Garay (1973) divided Angraecum into 19 sections based on floral morphology and vegetative traits [4]. Recent molecular work has confirmed that some sections are polyphyletic (e.g., section Pectinaria) and prompted re‑circumscription of five continental‑African members [6]. The most widely accepted sectional scheme now recognises 11 sections, each containing a cohesive set of species and often a distinct geographic focus (e.g., the Malagasy‑centric section Angraecum, the African section Pectinaria). When using a searchable index, filtering by section can drastically narrow results and highlight likely diagnostic characters.

4. Core diagnostic characters for Angraecum

The American Orchid Society describes Angraecum as monopodial epiphytes, lithophytes or terrestrials with a basal or along‑stem rooting system [4]. The following traits are most reliable for separating Angraecum from related genera such as Aerangis, Aeranthes or Jumellea:

• Leaf arrangement: distichous (two‑ranked) leaves are typical, though some species have terete leaves.
• Inflorescence: usually axillary racemes, sometimes branched; rarely solitary flowers.
• Floral structure: free sepals and petals, a lip that is generally entire (occasionally faintly three‑lobed), and a prominent spur that may be extremely long (e.g., A. sesquipedale with a 30 cm spur) [3].
• Pollinia: two, attached to a short stalk (viscidium) – a feature shared with many Vandeae but useful when combined with other characters.

These characters together form an informal key that can be applied in the field or when evaluating photographs. Detailed morphological keys are available in Garay’s 1973 monograph and in the recent revision of section Pectinaria [6], but the summary above is sufficient for most hobbyist identification.

5. Distinguishing Angraecum from close allies

While Angraecum shares the general Vandeae habit of long, pendulous inflorescences, several allied genera differ in key ways:

Scroll to explore the table →

These distinctions are discussed in the 2013 molecular‑morphological reclassification of the Angraecum‑alliance [9]. When a specimen shows a non‑resupinate flower with a lip that does not surround the column, Jumellea is a more likely identification.

6. Using a searchable index for Angraecum

Kew’s Plants of the World Online (POWO) provides a freely searchable interface that includes:

• Accepted names and synonyms (e.g., Angraecum calceolus Thouars) [1].
• Geographic distribution maps (country‑level) for each species.
• Sectional placement when available.
• Links to original publications and herbarium specimen images.

To locate a species:

1. Enter the genus Angraecum in the search bar.
2. Use the filter dropdown to narrow by region (e.g., “Madagascar”) or by section (e.g., “Pectinaria”).
3. Review the resulting list; accepted names are highlighted, while synonyms appear in smaller type.
4. Click a name to see the full taxon page, which includes a distribution map, synonymy, and bibliography.

Angraecum.org plans to mirror this functionality in its own species hub, providing a quick‑search box and alphabetical index. Until that tool is live, the Kew database remains the most authoritative source.

7. Example species and their diagnostic snapshots

Below are five widely referenced Angraecum species that illustrate the range of leaf‑ and flower‑morphologies used in identification. Data are drawn from the Kew entries and the AOS description.

Scroll to explore the table →

8. Limitations and ongoing revisions

Orchid taxonomy evolves quickly. Molecular phylogenies have revealed that Angraecum as traditionally circumscribed is not monophyletic, leading to the transfer of several species to genera such as Cryptopus or Sobennikoffia [11]. Consequently, a name found in older horticultural literature may now be a synonym of a different accepted species. Users should always cross‑reference the latest Kew checklist or recent monographs before making purchasing or conservation decisions.

Geographic coverage in databases also varies. Some species are known from a single herbarium specimen and lack reliable distribution maps (e.g., many newly described Malagasy taxa). The “searchable index” therefore reflects the best‑available data, not exhaustive field knowledge.

9. Practical steps for growers and researchers

1. Confirm the accepted name. Look up the species on POWO; note any listed synonyms.
2. Check sectional placement. Knowing the section can hint at ecological preferences (e.g., high‑elevation vs. low‑land species).
3. Match key morphological traits. Use the leaf‑arrangement, inflorescence type and spur length checklist above.
4. Record provenance. When acquiring a plant, document the label’s author citation and source country; this aids future taxonomic verification.
5. Stay updated. Subscribe to Kew’s taxonomic updates or the Orchid Society’s newsletters for new reclassifications.

Following these steps ensures that collections are accurately labelled, research data are reliable, and conservation assessments are based on current taxonomy.