''Caladenia excelsa'', commonly known as the giant spider orchid, is a species of orchid endemic to a small area in the south-west of Western Australia. It is a rare species with a single, hairy leaf and up to three cream-coloured to greenish-cream flowers with long, drooping sepals and

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

s. It is one of the tallest spider orchids in Western Australia and, with ''

Caladenia splendens ''Caladenia splendens'', commonly known as the splendid spider orchid, or splendid white 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 mostly white flow ...

'', has the largest flowers of any Western Australian orchid. Caladenia excelsa detail

Description

''Caladenia excelsa'' is a terrestrial, perennial, deciduous,

herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

with an underground tuber and a single erect, hairy leaf, long and wide. One or two cream-coloured to greenish-cream flowers long and wide are borne on a stalk tall. The sepals and petals have long, brownish, drooping thread-like tips. The dorsal sepal curves backwards behind the flower, long and wide at the base. The lateral sepals are long and wide at the base and taper to long, thin tips. The petals are long, wide at their bases and taper like the lateral sepals. The labellum is creamy-coloured with a red tip, long, wide and has many thin teeth up to long on its sides. There are four rows of maroon or white calli along the centre line of the labellum. Flowering occurs from late September to early November.

Taxonomy and naming

''Caladenia excelsa'' was first described by

Stephen Hopper Stephen Donald Hopper AC FLS FTSE (born 18 June 1951) is a Western Australian botanist. He graduated in Biology, specialising in conservation biology and vascular plants. Hopper has written eight books, and has over 200 publications to his n ...

and Andrew Brown in 2001 from a specimen collected by Hopper near Margaret River, Western Australia, Margaret River. The description was published in ''Nuytsia (journal), Nuytsia''. The Botanical nomenclature, specific epithet (''excelsa'') is a Latin word meaning "high" or "lofty" referring to the tallness of the flower spike.

Distribution and habitat

The giant spider orchid is found between Dunsborough, Western Australia, Dunsborough and Karridale, Western Australia, Karridale in the Jarrah Forest and Warren (biogeographic region), Warren IBRA, biogeographic regions where it grows in forests in deep sandy soils.

Conservation

''Caladenia excelsa'' is classified as "Declared Rare and Priority Flora List, Threatened Flora (Declared Rare Flora — Extant)" by the Western Australian Government Department of Parks and Wildlife (Western Australia), Department of Parks and Wildlife and it has also been listed 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, grazing (especially by the Western grey kangaroo), prescribed burning and infrastructure maintenance.

References

{{Taxonbar, from=Q15287581 Caladenia, excelsa Orchids of Western Australia Endemic orchids of Australia Plants described in 2001 Endemic flora of Southwest Australia Taxa named by Stephen Hopper Taxa named by Andrew Phillip Brown