Dendrobium speciosum

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Dendrobium speciosum
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Liliopsida Order: Asparagales Family: Orchidaceae Subfamily: Epidendroideae Tribe: Dendrobieae Subtribe: Dendrobiinae Genus: Dendrobium Species: D. speciosum
Binomial name
Dendrobium speciosum Sm., 1804

Dendrobium speciosum is not only a widespread Australian orchid but also a very variable orchid, forming a species complex. Its varieties can be found in wildly varying habitats as an epiphyte (on branches of rainforest trees) or a lithophyte (on sandstone in open forest) in a continuous distribution along the east coast of Australia and in distinct populations along the Tropic of Capricorn. As a lithophyte, it forms gigantic clumps on rocks and cliff faces with its roots forming dense, matted beds across the rock. It can be found from sea level to mountain tops.

This orchid is popular in cultivation. It is known under several common names : Captain King's Dendrobium, King Orchid, Pink Rock Orchid, Rock Lily. It was originally named by Sir James Edward Smith (1759-1828) from a specimen found at Port Jackson and sent to him by Surgeon General J White.

There are two to five thick, leathery leaves originating from the top of each pseudobulb. These leaves can remain on the plant for up to 12 years. The erect or curved pseudobulbs are rather large, up to 45 cm long. They are thickest at their base (5 to 7 cm), and often taper towards the apex (3cm). The showy flowers grow in long racemes on straight or slowly arching, long, starchy stems with over 100 flowers per stem from August to October. Their colour varies from white to creamy yellow. The white labellum is covered with purple dots and veined with red and purple. The roasted stems are edible

Synonyms, based on the same type, include :

• Callista speciosa (Sm.) Kuntze,(1891).
• Dendrobium speciosum var. typicum Domin (1915) , nom. inval.
• Dendrocoryne speciosum (Sm.) Brieger(1981)
• Tropilis speciosa (Sm.) Butzin (1982)
• Thelychiton speciosus (Sm.) M.A.Clem. & D.L.Jones (2002)

Dendrobium speciosum is a single variable species, forming a species complex overlapping in a continuum of variations. The following varieties, based on morphological data, have been proposed by Adams et al. (2006) ^[1]

• Dendrobium speciosum var. speciosum Sm, 1804
• Dendrobium speciosum var. hillii Mast., 1877
• Dendrobium speciosum var. grandiflorum F.M.Bailey, 1896 (also lithophytic)
• Dendrobium speciosum var. curvicaule F.M.Bailey, 1896
• Dendrobium speciosum var; pedunculatum Clemesha, 1981
• Dendrobium speciosum var. capricornicum Clemesha, 1982 (also lithophytic)
• Dendrobium speciosum var. boreale P.B.Adams, J.M.Burke & S.D.Lawson, 2006

with two new varieties :

• Dendrobium speciosum Sm. var. blackdownense P. B.Adams var. nov.
• Dendrobium speciosum Sm. var. carnarvonense P. B.Adams var. nov.

Some plants at the distribution limits especially of var. hillii do not fit a strict varietal description and are best designated by geographical location. Furthermore, all varieties are susceptible to cross pollination, giving rise to intervarietal seeds.

This species complex has been previously described by Dockrill in 1969 ^[2] and reviewed by several authors (Clemesha 1981a ^[3], 1981b ^[4], 1986 ^[5] , Clements 1989 ^[6], Banks & Clemesha 1990 ^[7] and Adams 1991 ^[8])

Dendrobium speciosum forms a natural hybrid with Dendrobium gracilicaule : Dendrobium × gracillimum. This hybrid has also been described as Dendrobium speciosum var. nitidum F.M.Bailey, , Dendrobium × nitidum (F.M.Bailey) M.A.Clem. & D.L.Jones , Dendrobium speciosum var. bancroftianum Rchb.f. and Dendrobium jonesii Rendle subsp. bancroftianum (Rchb.f.) M.A.Clem. & D.L.Jones .

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