Dendrophylax lindenii

Ghost orchid
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
Order: Asparagales
Family: Orchidaceae
Genus: Dendrophylax
Species: D. lindenii
Binomial name
Dendrophylax lindenii
(Lindl.) Benth. ex Rolfe
Synonyms[1][2]
  • Aeranthes lindenii (Lindl.) Rchb.f. in W.G.Walpers
  • Angraecum lindenii Lindl.
  • Polyrrhiza lindenii (Lindl.) Cogn.
  • Polyradicion lindenii (Lindl.) Garay
Dendrophylax lindenii

Dendrophylax lindenii, the ghost orchid (a common name also used for Epipogium aphyllum) is a perennial epiphyte from the orchid family (Orchidaceae). It is native to Florida, Cuba and the Bahamas.[1][3] Other common names include palm polly and white frog orchid.

Name

Its specific epithet "lindenii" is derived from its discoverer, the Belgian plant collector Jean Jules Linden who saw this orchid for the first time in Cuba in 1844. Much later it was also discovered in the Everglades in Florida.

Biology

Dendrophylax lindenii

Dendrophylax lindenii is a leafless epiphyte in the tribe Vandeae, in the subfamily Epidendroideae. The plant consists mainly of a network of photosynthetic roots on a tree trunk. Its habitat is moist, swampy forest in south-western Florida and Caribbean islands such as Cuba.

This orchid is exceptional among the monocots, in that it consists of a greatly reduced stem and its leaves have been reduced to scales. The flat, cord-like green roots constitute the bulk of the mature plant. They bear distinctive white "track marks", for which the technical term is pneumatodes and are believed to function partly like stomata, enabling the photosynthetic roots to perform the gas exchange necessary for respiration and photosynthesis. Chloroplasts in these flattened roots perform practically all the plant's photosynthesis. Their outer layer is an example of the velamen typical of most epiphytic orchids. Its functions include the absorption of nutrients and water, and admission of light for photosynthesis.

The species is endangered in the wild, and cultivation has proven exceptionally difficult, but while most attempts to raise seedlings into adult plants in sterile culture end in failure, some orchidists have in fact succeeded.[4] This orchid is listed on the Appendix II of CITES and is fully protected by Florida state laws, which forbid its removal from the wild. Plants collected from the wild typically do not survive removal from their habitat, and die within a year. In the wild, Dendrophylax lindenii typically grows on the central trunk or large main branches of living trees. It seems to prefer Annona glabra (pond-apple) trees, or occasionally Fraxinus caroliniana (pop ash) trees. It tends to attach to a tree at about eye-level or a few feet higher.

Dendrophylax lindenii blossoms between June and August, producing one to ten fragrant flowers that open one at a time. The flowers are white, 3–4 cm wide and 7–9 cm long. They are borne on spikes arising from the root network. Their most intense fragrance is in the early morning, the scent fruity, resembling an apple.[5] The lower petal, the labellum, has two long, lateral tendrils that twist slightly downward, resembling the hind legs of a jumping frog. Its bracts are scarious — thin and papery. The roots of this orchid are so well camouflaged on the tree that the flower may seems to float in mid-air, hence its name of "ghost orchid".


Origin and affinities

The genus Dendrophylax is a distant relative of the African and Indian Ocean genus Angraecum; at the time of the origin of the family Orchidaceae, the Atlantic ocean was still in parts a strait, permitting their common ancestors to establish in now widely separated Gondwanan regions.[6]

The giant sphinx moth, Cocytius antaeus is the only insect to have co-evolved with Dendrophylax to perform the necessary pollination. No other pollinator in its region has a proboscis long enough to access the nectar in the extremely long nectar spur of Dendrophylax. In this respect the plant-pollinator coevolution of the new-world moth and orchid present an example of convergence with the old-world Madagascan orchid Angraecum sesquipedale, which led Charles Darwin to predict that a long-tongued species of moth would be found to fertilize it. Years later the moth responsible was discovered: Morgan's hawk moth Xanthopan morgani. The larvae of the giant sphinx moth feed on Annona glabra (pond apple), the same trees D. lindenii is most intimately associated with.[7]

Cultivation

Plants can be successfully grown in a terrarium-like environment mounted bare root on a decay resistant, untreated wood stock in which the wood is laid horizontally on top of a bed of living sphagnum moss, as the plants require high humidity and stagnant air, or in a wardian case or greenhouse which approximates these conditions. Plants should not be allowed to cross pollinate and set seed unless the plant is very large, at least 10 inches across, as plants without sufficient biomass will transfer all of their stored reserves into making a very large seed pod and the plants behave much like an annual and die after seed set. These plants should be given 1/4 strength fertilizer in distilled or other low salt water sources weekly.

The plants are intolerant of water with high levels of dissolved salts and will result in the roots dying off from the tips. Continued exposure to chlorinated tap water will usually kill these plants, with the tips of the roots yellowing and rapidly dying back to the reduced stem. It is normal for the plants to periodically consume and dehise older roots, but this process does not yellow the roots, they simply shrivel and turn gray then dehise completely. Healthy plants will exhibit vigorous lime green root tips which are in an active state of growth. The plants root tips will grow continuously provided they receive bright light and regular fertilization and watering, with only a short resting period in late fall/early winter. Water should never be allowed to remain standing in the roots nor should any portion of the plants roots to be immersed in standing water for any significant period of time. The key to getting these plants to grow quickly is to keep the roots moist all the time when they are small without water standing in the roots, and regular fertilization. When the plants are small and their roots become dry these plants cease to grow appreciably. They like to be kept moist but not wet to stimulate increase in biomass and active root growth when small. The roots of these plants will also tend to produce new plantlets in a starfish like manner from broken or damaged roots or from roots which have grown longer than 12 inches, a growth habit shared with other members of the genus Dendrophylax.

Although plants in habitat occasionally experience light frost with some root tip damage, as a rule, the plants should not be subjected to freezing temperatures. Freezing temperatures except for very short periods will kill these plants in cultivation. Blooming is triggered by subjecting the plants to a cool, dry resting period with only very light misting every few weeks and lowering the humidity in the growing environment for a period of several months in late fall and early winter when the plants are large enough to support flowering, typically with a root mass of 7-8 inches across.

Newly forming flowers will appear from the highly reduced stem from the center of the root mass and are difficult to distinguish from aerial roots until the flower starts to develop. When new growth is apparent after giving the plants a resting period, resume normal watering. Plants which are large and have set seed pods should be given more frequent fertilizing and should limit only a single seed pod per plant by removing all but one seed pod from a plant. When attempting to produce seed pods from one of these plants, if the plant has multiple flowers all of them should be hand pollinated with pollenaria from a different plant if available, and only one seed pod allowed to remain on each plant, since not all of the flowers may successfully take. When mature, the pod contains thousands of microscopic dust-like seeds.

In habitat, successful pollination of this species appears to be an infrequent, but not rare, event. The plants also flower irregularly in habitat, and some years do not flower at all.[8]

The plant plays a pivotal role in the non-fiction book The Orchid Thief, by Susan Orlean and the movie based on the book, Adaptation. The ghost orchid of Blair Audubon Corkscrew Swamp Sanctuary also inspired the fiction novel, Ghost Orchid by D. K. Christi.

References

  1. 1 2 Kew World Checklist of Selected Plant Families
  2. ↑ B. S. Carlsward, W. M. Whitten & N. H. Williams (2003). "Molecular phylogenetics of neotropical leafless Angraecinae (Orchidaceae): reevaluation of generic concepts" (PDF). International Journal of Plant Sciences. 164 (1): 43–51. doi:10.1086/344757.
  3. ↑ Florida of North America, v 26 p 621, Dendrophylax lindenii
  4. ↑ Link to blooming cultivated ghost orchid on the Orchid Source Forum - Link to 2nd blooming ghost orchid on the Orchid Source Forum
  5. ↑ Sadler, James; Jaclyn Smith; Lawrence Zettler; Hans Alborn; Larry Richardson (2011). "Fragrance composition of Dendrophylax lindenii (Orchidaceae) using a novel technique applied in situ". European Journal of Environmental Sciences. 1 (2): 137–141.
  6. ↑ Yohan Pillon & Mark W. Chase (2007). "Taxonomic exaggeration and its effects on orchid conservation". Conservation Biology. 21 (1): 263–265. doi:10.1111/j.1523-1739.2006.00573.x. PMID 17298532.
  7. ↑ "Silkmoths". Silkmoths.bizland.com. 2011-01-31. Archived from the original on 2016-03-04. Retrieved 2011-11-01.
  8. ↑ Illustrated Encyclopedia of Orchids ISBN 0-88192-267-6
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