''Caladenia arenaria'', commonly known as the sand-hill spider orchid, is a plant in the orchid family

Orchidaceae 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. Along with the Asteraceae, they are one of the two largest families of flowering ...

and is

endemic Endemism is the state of a species being found 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 found elsew ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. It is a ground orchid with a single, densely hairy leaf and one or two white or pale yellow flowers with maroon tips. Formerly much more widespread, it is now only known from about two thousand individual plants in five locations in the Riverina area and is classed as "Endangered".

Description

''Caladenia arenaria'' is a terrestrial,

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

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 a single underground tuber which is replaced annually. In late autumn or early winter a linear to narrow lance-shaped leaf is produced which is long, wide and reddish at the base. One or (rarely) two pale yellow to creamy-white flowers are borne on a hairy spike up to high. The dorsal

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 The term ''sepalum'' was coined b ...

, lateral 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 are up to long, held horizontally or slightly drooping and tapering to dark reddish, thread-like ends. The labellum is egg-shaped to heart-shaped, about long and wide with teeth up to but decreasing in size towards the front of the labellum. There are four to six rows of calli, shaped like golf stick heads on the centre of the labellum. Flowering occurs from late August to November.

Taxonomy and naming

''Caladenia arenaria'' was first formally described by

Robert FitzGerald Robert Stuart Fitzgerald (; 12 October 1910 – 16 January 1985) was an American poet, literary critic and translator whose renderings of the Greek classics "became standard works for a generation of scholars and students".Mitgang, Herbert (Janua ...

in 1882 and the description was published in his book, ''Australian Orchids''. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

(''arenaria'') is a

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

word meaning "sandy".

Distribution and habitat

Sand-hill spider orchid grows in

sclerophyll Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaf, leaves, short Internode (botany), internodes (the distance between leaves along the stem) and leaf orientation which is paral ...

forest and on sandhills, usually under

cypress pine Cypress-pine is the common name used for three closely related genera of conifers in the cypress family Cupressaceae: *'' Callitris'' (Australia) *'' Actinostrobus'' (Australia) *''Widdringtonia ''Widdringtonia'' is a genus of coniferous tree ...

trees. Its range used to extend for from Deniliquin to

Yass Yass may refer to: People * Catherine Yass (born 1963), painter * Yazz, a British pop singer from the 1980s and 1990s * Jeff Yass (born 1956), options trader, managing director and one of the five founders of the Philadelphia-based Susquehanna I ...

and Mudgee but is now only known from five locations between

Urana Urana is a small town in the Riverina region of New South Wales, Australia. The town is in the Federation Council local government area. Urana is located between Lockhart and Jerilderie, about southwest of the state capital, Sydney. To the wes ...

and Narrandera.

Conservation

''Caladenia arenaria'' is listed as "Endangered" under the New South Wales ''Threatened Species Conservation Act'' and under the Commonwealth Government '' Environment Protection and Biodiversity Conservation Act 1999'' (EPBC) Act. Five populations with a total of about two thousand individual plants are known. Weeds, grazing and hybridisation with other orchid species are the main threats to the survival of this species.

References

{{Taxonbar, from=Q9673297 arenaria Plants described in 1882 Endemic orchids of Australia Orchids of New South Wales Taxa named by Robert D. FitzGerald