''Pterostylis excelsa'', commonly known as the tall rustyhood, or dry land green-hood is a flowering plant in the orchid family Orchidaceae and is endemic to South Australia. It has a rosette of leaves and when flowering, up to twenty green or brown flowers which lean forward and have a thick, fleshy, partly hairy, insect-like labellum.

Description

''Pterostylis 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. It has a rosette of between five and twenty leaves long and wide. Flowering plants have a rosette at the base of the flowering spike but the leaves are usually withered by flowering time. Between two and twenty green, brown or green and brown flowers with translucent panels and long, wide are borne on a flowering spike tall. The flowers lean forward and there are between three and eight stem leaves wrapped around the flowering spike. The dorsal sepal 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 form a hood or "galea" over the column with the dorsal sepal having a narrow tip long. The lateral sepals turn downwards, are about the same width as the galea and suddenly taper to narrow tips long. The labellum is thick, fleshy, insect-like, long and about wide with short hairs on the "head" end and longer ones on the sides of the "body". Flowering occurs from August to December.

Taxonomy and naming

''Pterostylis excelsa'' was first formally described in 1986 by Mark Clements from a specimen grown in the

Australian National Botanic Gardens The Australian National Botanic Gardens (ANBG) is a heritage-listed botanical garden located in , Canberra, in the Australian Capital Territory, Australia. Established in 1949, the Gardens is administered by the Australian Government's Departme ...

from a tuber collected from the Eyre Peninsula. The description was published in the fourth edition of the ''Flora of South Australia''. 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 ...

(''excelsa'') is a Latin word meaning "high", "lofty" or "distinguished". In 1941, William Nicholls described ''Pterostylis squamata'' var. ''valida'' and in 1994, David Jones raised it to species status as ''Pterostylis valida''. However, this name is regarded as a synonym of ''Pterostylis excelsa''.

Distribution and habitat

The tall rustyhood is widespread and locally common in the south-east of South Australia, sometimes growing in large colonies. It grows in scrubland and mallee, sometimes on rock outcrops in areas receiving an average annual rainfall of .

References

{{Taxonbar, from=Q15491537 excelsa Endemic orchids of Australia Orchids of South Australia Plants described in 1986