Caladenia viridescens

Caladenia viridescens, commonly known as the Dunsborough spider orchid, is a species of orchid endemic to the south-west of Western Australia. It has a single erect, hairy leaf and up to three pale greenish-yellow flowers with faint red or pink markings.

Dunsborough spider orchid
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Genus: Caladenia
Species:
C. viridescens
Binomial name
Caladenia viridescens
Synonyms[1]

Calonemorchis viridescens (Hopper & A.P.Br.) Szlach. & Rutk.

Description

Caladenia viridescens is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect leaf, 150–200 mm long and 5–8 mm wide. Up to three greenish-yellow flowers with faint red or pink markings and 50–70 mm across are borne on a stalk 250–400 mm high. The sepals have thick, brownish, club-like, densely glandular tips 5–8 mm long. The dorsal sepal is erect, 40–50 mm long and about 3 mm wide. The lateral sepals are 40–50 mm wide, 3–7 mm long and spread apart from each other with their tips curving downwards. The petals are 35–40 mm long, about 3 mm wide and held horizontally or slightly curved downwards. The labellum is 17–22 mm long, 10–14 mm wide and greenish-yellow with red lines and a dark red tip. The side of the labellum have narrow, red teeth up to 4 mm long, the tip curls under and there are four rows of dark red calli up to 1.5 mm long, along its mid-line. Flowering occurs from September to November.[2][3][4][5]

Taxonomy and naming

Caladenia viridescens was first described in 2001 by Stephen Hopper and Andrew Phillip Brown from a specimen collected at Cape Naturaliste and the description was published in Nuytsia.[1] The specific epithet (viridescens) is derived from the Latin words viridis meaning "green"[6]:837 and the suffix -escens meaning "becoming"[6]:44 referring to the pale green colour of the flowers of this orchid.[3]

Distribution and habitat

The Dunsborough spider orchid is only known from between Yallingup and Busselton in the Jarrah Forest biogeographic region where it grows in shrubby woodland.[2][3][4][7]

Conservation

Caladenia viridescens is classified as "Threatened Flora (Declared Rare Flora — Extant)" by the Western Australian Government Department of Parks and Wildlife[7] and as "Endangered" (EN) under the Australian Government Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The main threats to the species are weed invasion and grazing and digging by mammals including rabbits, kangaroos, bandicoots and livestock.[5]

References
  1. "Caladenia viridescens". APNI. Retrieved 28 March 2017.
  2. Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 84. ISBN 1877069124.
  3. Brown, Andrew; Dundas, Pat; Dixon, Kingsley; Hopper, Stephen (2008). Orchids of Western Australia. Crawley, Western Australia: University of Western Australia Press. p. 108. ISBN 9780980296457.
  4. Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia (3rd ed.). Gooseberry Hill: Noel Hoffman. p. 128. ISBN 9780646562322.
  5. Patten, Julie; Webb, Andrew; Batty, Andrew. "Dunsborough spider orchid (Caladenia viridescens) recovery plan" (PDF). Australian Government Department of the Environment. Retrieved 28 March 2017.
  6. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
  7. "Caladenia viridescens". FloraBase. Western Australian Government Department of Parks and Wildlife.
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