Pterostylis robusta

Pterostylis robusta, commonly known as the sharp-leaf greenhood, is a species of orchid endemic to south-eastern Australia. As with similar orchids, the flowering plants differ from those which are not flowering. The non-flowering plants have a rosette of leaves but the flowering plants have a single flower with leaves on the flowering spike. This greenhood has a relatively large green, white and reddish-brown flower with reddish-brown stripes with the labellum just visible inside the flower.

Sharp-leaf greenhood
Pterostylis robusta growing near Charlton
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Cranichideae
Genus: Pterostylis
Species:
P. robusta
Binomial name
Pterostylis robusta
Synonyms[2]

Description

Pterostylis robusta is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of four to ten, dark green, egg-shaped leaves. Each leaf is 10–25 mm long and 10–16 mm wide. Flowering plants have a single flower 27–35 mm long and 10–12 mm wide borne on a spike 50–200 mm high with three to seven spreading stem leaves. The flowers are green, white and brownish with a reddish-brown tinge or stripes. The dorsal sepal and petals are fused, forming a hood or "galea" over the column. The dorsal sepal curves forward with a sharp point 2–4 mm long. The lateral sepals are erect, held closely against the galea, have an erect, thread-like tip 20–30 mm long and a flat sinus with a small notch between their bases. The labellum is 12–15 mm long, 3–4 mm wide, dark brown or green and just visible inside the flower. Flowering occurs from April to August.[3][4][5][6]

Taxonomy and naming

Pterostylis robusta was first formally described in 1927 by Richard Sanders Rogers and the description was published Transactions and Proceedings of the Royal Society of South Australia.[1][7] The specific epithet (robusta) is a Latin word meaning "strong like oak" or "robust".[8]

Distribution and habitat

The sharp-leaf greenhood is most common in the higher rainfall areas of South Australia where it sometimes forms extensive colonies. In Victoria it grows in open forest in the north-west of the state but it is rare in New South Wales where it grows on sheltered ridges south from Wagga Wagga.[3][4][5][6]

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References
  1. "Pterostylis robusta". APNI. Retrieved 25 May 2017.
  2. "Pterostylis robusta". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  3. Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. pp. 292–293. ISBN 978-1877069123.
  4. Jeanes, Jeff. "Pterostylis robusta". Royal Botanic Gardens Victoria: vicflora. Retrieved 25 May 2017.
  5. Jones, David L. "Pterostylis robusta". Royal Botanic Garden Sydney: plantnet. Retrieved 25 May 2017.
  6. "Pterostylis robusta". State Herbarium of South Australia: eflora SA. Retrieved 25 May 2017.
  7. Rogers, Richard Sanders (1927). "Contribution to the Orchidology of Australia". Transactions and Proceedings of the Transactions and Proceedings of the Royal Society of South Australia. 51: 296–297. Retrieved 25 May 2017.
  8. Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press. p. 556.
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