''Dendrobium tetragonum'', commonly known as the tree spider orchid,
is a variable species of
epiphytic
An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...
or
lithophytic
Lithophytes are plants that grow in or on rocks. They can be classified as either epilithic (or epipetric) or endolithic; epilithic lithophytes grow on the surfaces of rocks, while endolithic lithophytes grow in the crevices of rocks (and are also ...
orchid
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to eastern
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. Tree spider orchids are unusual in having pendulous
pseudobulb
In botany, a pseudobulb is a storage organ found in many epiphytic and terrestrial sympodial orchids. It is derived from a thickening of the part of a stem between leaf nodes and may be composed of just one internode or several, termed ''heter ...
s that are thin and wiry near the base then expand into a fleshy, four-sided upper section before tapering at the tip. There are only a few thin but leathery leaves at the end of the pseudobulbs and up to five flowers on relatively short flowering stems. To allow for the variations in the species there are five subspecies and a variety, some with a unique common name.
Description
''Dendrobium tetragonium'' is an epiphytic or lithophytic
herb
Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...
with pendulous pseudobulbs long and wide. The pseudobulbs have a thin, wiry base but expand to a fleshy, four-sided upper section and a tapering tip with between two and five thin but leathery leaves. The leaves are long and wide. The flowering stems are long and bear up to eight flowers. The number, size and colour of the flowers depend on subspecies. Flower size ranges from long and wide. The flowers range in colour from green to pale yellow, sometimes with red blotches and a
labellum that ranges in colour from white, to yellowish with red, brown or purplish markings. The
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106
Etymology
The term ''sepalum'' ...
s range in size from long and wide and the
petal
Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...
s from long and wide. The labellum ranges from long and from wide. Flowering occurs between April and November.
Taxonomy and naming
''Dendrobium tetragonum'' was first formally described in 1839 by
Allan Cunningham from a specimen "hanging loosely from the stems of small trees in ''dry'' shaded woods,
Moreton Bay
Moreton Bay is a bay located on the eastern coast of Australia from central Brisbane, Queensland. It is one of Queensland's most important coastal resources. The waters of Moreton Bay are a popular destination for recreational anglers and are ...
". The description was published in ''
Edwards's Botanical Register
''The Botanical Register'', subsequently known as ''Edwards's Botanical Register'', was an illustrated horticultural magazine that ran from 1815 to 1847. It was started by the botanical illustrator Sydenham Edwards, who had previously illustrat ...
'' edited by
John Lindley
John Lindley Fellow of the Royal Society, FRS (5 February 1799 – 1 November 1865) was an English botanist, gardener and orchidology, orchidologist.
Early years
Born in Old Catton, Catton, near Norwich, England, John Lindley was one of four c ...
.
Subdivisions
* ''Dendrobium tetragonum'' var. ''cacatua''
( D.L.Jones & M.A.Clem.) H.Mohr – the yellow tree spider orchid has greenish to pale yellow flowers with a few fine reddish purple markings and a white labellum, usually with no markings, and flowers from July to September;
* ''Dendrobium tetragonum'' subsp. ''cataractarum''
Peter B.Adams, S.D.Lawson & G.A.Peterson has yellowish green flowers with red, purple or brown marks on the edge of the sepals and a pale, cream-coloured labellum with reddish purple markings, and flowers from August to September;
* ''Dendrobium tetragonum'' subsp. ''giganteum''
( Leaney) Peter B.Adams – the blotched tree spider orchid has greenish yellow flowers with prominent red blotches and a white labellum with red and purplish lines, and flowers from April to November;
* ''Dendrobium tetragonum'' subsp. ''melaleucaphilum''
( D.L.Jones & M.A.Clem.) Dockrill – the flared tree spider orchid has the largest flowers in the species, the flowers green to greenish yellow with reddish blotches and a white or pale yellow labellum with red or purplish marks, and flowers from May to October;
* ''Dendrobium tetragonum'' subsp. ''serpentis''
Peter B.Adams has flowers that are green at first, then turn yellow with few or no markings apart from on the labellum which is white to pale cream-coloured with reddish purple markings, and flowers from August to September;
* ''Dendrobium tetragonum'' subsp. ''tetragonum''
– the banded tree spider orchid has the smallest flowers of the species, the flowers green to greenish yellow with dark reddish brown bands on the edges and a cream-coloured or yellow labellum with brown, red or purplish marks, and flowers from May to October.
Distribution and habitat
Tree spider orchids are usually epiphytes which grow on trees in rainforest or shady places beside streams, but also sometimes on
paperbark
''Melaleuca'' () is a genus of nearly 300 species of plants in the myrtle family, Myrtaceae, commonly known as paperbarks, honey-myrtles, bottlebrushes or tea-trees (although the last name is also applied to species of '' Leptospermum''). They ...
trees, especially ''
Melaleuca styphelioides'' and occasionally on rocks. Different forms of the species occur in different areas of coastal or near-coastal
New South Wales
New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...
and
Queensland
Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
.
* ''Dendrobium tetragonum'' var. ''cacatua'' is found from the Mount Windsor Tableland near
Cape Tribulation
Cape Tribulation is a headland and coastal locality in the Shire of Douglas in northern Queensland, Australia. In the , Cape Tribulation had a population of 123 people.
Geography
The locality is north of Cairns. It is within the Daintree N ...
to the
Eungella National Park
Eungella National Park ( ; meaning "Land of the clouds") is a protected area in Queensland, Australia. It is on the Clarke Range at the end of the Pioneer Valley 80 km west of Mackay, and 858 km northwest of Brisbane. Eunge ...
in Queensland;
* Subspecies ''cataractarum'' is restricted to Connors Range west of the
Cape Palmerston National Park in central eastern Queensland;
* ''Dendrobium tetragonum'' subsp. ''giganteum'' occurs between the
Iron Range
The Iron Range is collectively or individually a number of elongated iron-ore mining districts around Lake Superior in the United States and Canada. Much of the ore-bearing region lies alongside the range of granite hills formed by the Giants ...
and
Mackay in Queensland;
* ''Dendrobium tetragonum'' subsp. ''melaleucaphilum'' is found from the
Blackdown Tableland National Park
Blackdown Tableland is a national park in the Central Highlands Region, Queensland, Australia.
Geography
The park is in Central Queensland, northwest of Brisbane. The mountainous terrain of the tablelands provides a unique landscape featuring ...
in Queensland to the
Blue Mountains in New South Wales;
* ''Dendrobium tetragonum'' subsp. ''serpentis'' is restricted to the northern parts of the Blackdown Tableland;
* ''Dendrobium tetragonum'' subsp. ''tetragonum'' ranges from
Fraser Island
K'gari ( , ), also known by its former name Fraser Island, is a World Heritage-listed sand island along the south-eastern coast in the Wide Bay–Burnett region of Queensland, Australia. The island lies approximately north of the state capi ...
in Queensland to
Tomerong in New South Wales.
References
External links
Atlas of Living Australia, ''Dendrobium tetragonum'' A.Cunn. Tree Spider OrchidAndy's Orchids (Encinitas California): ''Dendrobium tetragonum'' subsp. ''giganteum''
{{DEFAULTSORT:Dendrobium Tetragonum
tetragonum
Endemic orchids of Australia
Orchids of New South Wales
Orchids of Queensland
Plants described in 1839