Angraecum Explained

Angraecum, also known as comet orchid,[1] [2] [3] is a genus of the family Orchidaceae native to tropical and South Africa, as well as Sri Lanka. It contains 223 species.

Etymology

Despite the genus's distribution being largely confined to Africa and its offshore islands, the genus name is a latinization of the Indonesian and Malay word anggrek ("orchid"), itself ultimately from Javanese ꦲꦔ꧀ꦒꦿꦺꦏ꧀ (anggrék, "orchid").[4] [5] [6] [7]

Description

Angraecums are quite varied vegetatively and florally, and are adapted to dry tropical woodland habitat and have quite fleshy leaves as a consequence. Most are epiphytes, but a few are lithophytes.

The long-lasting flowers are racemose and grow from the leaf axils. They are mostly white, but a few are yellow, green or ochre. They all have a long spur at the back of the labellum (lip).

In the case of Angraecum sesquipedale, a species from Madagascar, on observing the spur in the lip, Charles Darwin made the hypothesis that, since the nectar was at the bottom of the spur, a pollinator must exist with a tongue at least that long. Otherwise the orchid could never be pollinated. At the time, he was not believed. However, in 1903, the predicted pollinator was discovered, a hawk moth then named Xanthopan morganii praedicta ("praedicta" meaning "the predicted one"). It has an appropriately long proboscis. The specific name sesquipedale means "one foot and a half", referring to the length of the spur. This is an example of mutual dependence of an orchid and a specific pollinator.

Distribution

Tropical Africa and Madagascar contain the majority of the genus with one outlier found on Sri Lanka, and three species once thought to belong to the genus in Japan and the Philippines. But these orchids can also be found on the Comoros, the Seychelles, and the Mascarenes. They occur between sea level and in humid regions.

Ecology

Pollination

The most commonly known example of Angraecum pollination is the relationship of Angraecum sesquipedale, which is pollinated by the moth species Xanthopan morganii praedicta[8] However, different modes of pollination are known to occur in Angraecum. Bird pollination has been reported to occur in Angraecum striatum, which is pollinated by the bird species Zosterops borbonicus Boddaert.[9] [10] Angraecum cadetii is pollinated by the cricket species Glomeremus orchidophilus.[11] [12] There have also been speculations regarding pollination of Angraecum cadetii Bosser and Angraecum bracteosum Balf. & S. Moore through the lizard species Phelsuma borbonica [13]

Conservation

Many species of Angraecum orchid are considered to be at risk of extinction in the wild and are protected from international trade under CITES.[14] The genus Angraecum is listed as one of the top conservation priorities by the International Union for Conservation of Nature and Natural Resources (IUCN) Orchid Specialist Group. Many of the species, such as Angraecum sororium, are endemic to Madagascar and are threatened from over collecting, loss of hawkmoth pollinators, habitat fragmentation, and fire.[15]

Horticulture

In horticulture the generic name is abbreviated as Angcm.[16] Like all other orchids it is best to water in the mornings to avoid fungal rot due to overnight dampness. Feeding as per other orchids and similar light conditions: in humid and hot regions (sub tropical) feed fortnightly during growing season (Summer) with a certified orchid fertiliser following directions on packet, weaker solutions are also okay if you're worried. In summer water weekly or more depending on situation. Angraecums flower best when in a lighter position. Keep out of direct sunlight as this can damage (and eventually kill) the plant. Most Angraecums will have their leaves for a number of years so any sun burn spots are ugly for a significant period and also may expose your plant to disease. In indirect sunlight the Angraecums will reward you with blooms and attractive growth.

Angraecum Veitchii

a very rewarding orchid. In indirect light and watered/fed regularly this plant will produce blooms annually (usually in late Winter to Spring - for Australia this occurs in August). The flowers last a while if kept in a sheltered position and their strong heady fragrance is delightful. They only release their perfume at night. Flowers are large (4– across), waxy, white to greenish cream in colour and borne on stems of seven to ten depending on the faithfulness of your fertilising, watering, and indirect light provision. The leaves are large, thick straps that alternately fan out from a central (monopodal) stem. Pups (keikis) form at the base of the stem and can either be divided from the parent plant once they have at least three roots of their own or alternatively, left on the plant these will make a stunning specimen as when mature will produce blooms with the parent plant - many award-winning angraecum veitchiis are grown as such. In the right conditions these orchids are healthy and require little attention. As they are epiphytes the potting mixture should be loose and free draining. Prolific roots are formed from the base and also amongst the lower half of the foliage. These can be troublesome when moving the plant. Once your angraecum is big it is best to pot it in a heavy terracotta pot or place a brick in the bottom of the pot in order to ensure the plant does not get top heavy and risk snapping when blown over in the wind, especially since they flower during the windier times of the year. When watering a good soaking with a hose or watering-can is best (not just a misting from a spray gun) as this helps to flush away any salts from fertilisers that may be present in the potting mixture and also thoroughly wets the plant. Make sure the roots halfway up the stem get a soaking too, not just the potted roots.

Hybrids

Notes and References

  1. Darwin Orchid (Comet Orchid, Star of Bethlehem). (2019, August 14). Gothenburg Botanical Garden. Retrieved January 16, 2023, from https://www.botaniska.se/en/research--collections/collections/tropical-orchids/darwin-orchid-comet-orchid-star-of-bethlehem/
  2. Comet Orchid at the Orchid Room. (n.d.). Friends of the Port St Lucie Botanical Gardens. Retrieved January 16, 2023, from https://www.pslbg.org/comet-orchid.html
  3. Comet Orchid Angraecum spp. (n.d.). Candide. Retrieved January 16, 2023, from https://candide.com/ZA/plants/c3598b40-e27d-4a16-b3f8-315c62f8db0c
  4. Web site: Angraecum . American Orchid Society . 10 December 2022.
  5. Web site: ANGRAECUM, THE WHITE ORCHID OF MADAGASCAR . Orchid Republic . 10 December 2022.
  6. Merriam-Webster. (n.d.). Angrecum. In Merriam-Webster.com dictionary. Retrieved January 16, 2023, from https://www.merriam-webster.com/dictionary/Angrecum
  7. Quattrocchi, U. (1999). "CRC World Dictionary of Plant Names: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology." p 143. Taylor & Francis.
  8. Arditti, J., Elliott, J., Kitching, I. J., & Wasserthal, L. T. (2012). "‘Good Heavens what insect can suck it’–Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta." Botanical Journal of the Linnean Society, 169(3), 403-432.
  9. Micheneau, C., Fournel, J., Humeau, L., & Pailler, T. (2008). "Orchid–bird interactions: a case study from Angraecum (Vandeae, Angraecinae) and Zosterops (white-eyes, Zosteropidae) on Reunion Island." Botany, 86(10), 1143-1151.
  10. Micheneau, C., Fournel, J., & Pailler, T. (2006). "Bird pollination in an angraecoid orchid on Reunion Island (Mascarene Archipelago, Indian Ocean)." Annals of Botany, 97(6), 965-974.
  11. Micheneau, C., Fournel, J., Warren, B. H., Hugel, S., Gauvin-Bialecki, A., Pailler, T., ... & Chase, M. W. (2010). "Orthoptera, a new order of pollinator." Annals of botany, 105(3), 355-364.
  12. Fournel, J., Micheneau, C., & Baider, C. (2015). "A new critically endangered species of Angraecum (Orchidaceae), endemic to the island of Mauritius, Indian Ocean." Phytotaxa, 222(3), 211-220.
  13. Bègue, J. F., Sanchez, M., Micheneau, C., & Fournel, J. (2014). "New record of day geckos feeding on orchid nectar in Reunion Island: can lizards pollinate orchid species?." Herpetology Notes, 7, 689-692.
  14. Angraecum. (n.d.). Convention on International Trade in Endangered Species of Wild Fauna and Flora. Retrieved January 16, 2023, from https://cites.org/eng/taxonomy/term/13325
  15. Conservation of Madagascar's granite outcrop orchids: influence of fire and moisture. April 2011 . Whitman . Melissa . Medler. Michael . Randriamanindry . Jean Jacques. Rabakonadrianina . Elisabeth . Lankesteriana. 11. 1 . 55–67. 10.15517/lank.v11i1.18315 . 1409-3871.
  16. Orchid Species: Angraecum sesquipedale. (n.d.). International Orchid Foundation (IOF). Retrieved January 16, 2023, from https://www.orchids.org/grexes/angraecum-sesquipedale

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