At a glance
RECORDED PROFILE DATA- Scientific name
- Angraecum sororium Schltr.
- Name status
- Accepted
- Native region
- Madagascar
- Growth habit
- Lithophytic, clump‑forming
- Cultivation temperature group
- Cool‑growing (tolerates near‑freezing nights)
Names and Taxonomy
The accepted scientific name is Angraecum sororium Schltr. The name is listed as accepted in Kew’s Plants of the World Online database and was originally published in Repert. Spec. Nov. Regni Veg. Beih. 33: 360 (1925) [10]. No synonyms or spelling variants are recorded in the cited sources. Common names are not documented in the available references.
How to Identify This Species
Angraecum sororium is a lithophytic, clump‑forming orchid. Mature plants reach 0.5–1 m in height, with a short stem bearing two rows of stiff, ligulate, shiny green leaves that are unequally bilobed at the tip [2][4]. The leaves are confined to the upper quarter of the stem, leaving the lower portion bare or covered with dry brown sheaths [4].
The inflorescence is an axillary, slender raceme that typically carries 1–4 flowers. Flowers are white, waxy, and about 12.5 cm (5 in) across [4]. Each flower possesses a long, green spur‑like nectary extending from the lip; the spur length is not quantified in the sources but is described as “extraordinary” in pollination studies [5]. The fragrance is strong and released at night, described as “spicily” scented [2].
In the field the species grows among boulders and granite outcrops, often in almost full sun but moderated by frequent fog and mist [2][8]. These habitat cues help distinguish it from other Angraecum species that are primarily epiphytic.
Native Range and Habitat
The species is endemic to Madagascar, occurring in the central highlands at elevations of roughly 1 600–2 200 m [4][8]. It is lithophytic, growing on rocks, boulders and among decaying leaf litter in open, sun‑exposed sites where mist provides moisture [2][8]. Seasonal frost and brief early‑morning freezes are reported in its native habitat [8].
Species‑Specific Care
| Factor | Documented guidance | Source |
|---|---|---|
| Light | Bright, almost full sun; in cultivation filter with shade cloth or place near a sunny window; avoid scorching. | RHS [2]; Marniturkel [8] |
| Temperature | Cool‑growing; tolerates night temperatures down to near 0 °C (freezing) in winter; daytime 15–25 °C. | RHS hardiness ratings H5–H7 [2]; field observations of frost [8] |
| Humidity & Airflow | Good air movement; benefit from frequent fog or mist; moderate humidity (50–70 %). | RHS [2]; Hillerman notes importance of airflow for lithophytes [9] |
| Medium | Well‑draining, moisture‑retentive mix such as fine sand, perlite, lava rock or pumice combined with fine fir bark and leaf mould; avoid coarse fir bark. | Marniturkel [8]; Hillerman [9] |
| Watering | Keep medium moist but not waterlogged; allow the mix to dry slightly between waterings; increase moisture during the active growth period. | RHS [2]; Hillerman [9] |
| Feeding | Balanced orchid fertilizer at half strength applied monthly during growth. | General orchid practice (Hillerman [9]); specific dosage not documented. |
| Repotting | Repot every 2–3 years using the recommended lithophytic mix; prune dead sheaths. | Hillerman [9] (general for cool‑growing Angraecum). |
| Seasonal change | Provide cooler night temperatures in winter to mimic native highland climate; no specific rest period documented. | RHS [2]; field frost reports [8] |
Overall, successful cultivation replicates the species’ natural high‑altitude, rock‑dwelling environment: bright light, excellent drainage, cool nights, and regular airflow.
Flowering and Pollination
In its native range the plant flowers from January to March, producing up to four white, night‑scented flowers per inflorescence [2]. The flowers are long‑lasting and emit fragrance after dusk, attracting nocturnal hawkmoths. A field study documented that Coelonia solani pollinates A. sororium on Mt. Angavokely in central Madagascar [5]. The long spur and landing platform of the lip facilitate deep proboscis insertion by these moths.
Evidence and Limitations
Most morphological and ecological data come from horticultural descriptions (RHS, Marniturkel) and a limited pollination study. Quantitative measurements such as exact spur length, precise humidity requirements, or detailed temperature minima are not provided in the cited sources. Conservation status and legal trade information were not found in the available references.
Frequently asked questions
When does Angraecum sororium flower in cultivation?
In cultivation the plant typically blooms from January to March, mirroring its natural flowering period in the central highlands of Madagascar.
What type of substrate is best for Angraecum sororium?
A well‑draining, moisture‑retentive mix such as fine sand, perlite, lava rock or pumice combined with fine fir bark and leaf mould is recommended; coarse fir bark should be avoided.
Can Angraecum sororium tolerate freezing temperatures?
Yes, field observations report brief early‑morning freezes in its native habitat, and RHS hardiness ratings indicate the species can survive temperatures down to 0 °C or slightly below.
FOLLOW THE EVIDENCE
Sources & references
- Angraecum Bory | Plants of the World Online | Kew Science – https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:325979-2
- Angraecum sororium – RHS – https://www.rhs.org.uk/plants/1293/angraecum-sororium/details
- Angraecum sororium – orchidroots – https://orchidroots.com/display/summary/orchidaceae/9694/
- IOSPE PHOTOS – Angraecum sororium – https://www.orchidspecies.com/angsororium.htm
- The Pollinators of the Malagasy Star Orchids – https://doi.org/10.1111/j.1438-8677.1997.tb00650.x
- Angraecum sororium – Marniturkel – https://marniturkel.com/mostlyspecies/f.ang.sor.2895.html
- Cultural Requirements of Angraecum by Fred E. Hillerman – https://docslib.org/doc/9024324/cultural-requirements-of-angraecum-by-fred-e-hillerman
- Angraecum sororium Schltr. — The Plant List – http://www.theplantlist.org/tpl1.1/record/kew-9694
