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Frog Greenhood
Pterostylis sargentii C.R.P.Andrews 1905

Synonyms

Notes

The Frog Greenhood is one of the most distinct species among the Banded Greenhood Orchids and readily identified by the long, pointy ends to its lateral sepals and the unique, dark, anvil-shaped labellum. As with all Banded Greenhoods, the labellum is irritable and will flick up when touched, thereby bringing the pollinator in contact with the stigma and pollen. The colour of the flowers is generally quite variable and can range from green to brown.

The Frog Greenhood is common and widespread across WA’s Wheatbelt region south-west of a line from Kalbarri to Israelite Bay where it grows in large numbers in dry forests and woodland. It is particularly common in open wandoo woodland where it thrives in rather harsh conditions in dry bark and leaf litter in places where few other plants manage to survive. Accompanying species include the Little Pink Fairy Orchid and the Sugar Orchid, both of which are equally abundant throughout the Wheatbelt.

What makes the Frog Greenhood peculiar is the fact that it appears to have a rather extended flowering period. The main flowering period is July and August when the orchids are abundant across most of the Wheatbelt. In some parts of the Wheatbelt a second generation of plants then begins to flower several weeks later during September and October. As shown in Fig. 11, there appear to be subtle differences in the structure and shape of the labellum between the early-flowering and late-flowering varieties. Early-flowering plants have a rather broad, smooth, anvil-shaped labellum, while the labellum of the late-flowering variety is slender, banana-shaped and densely covered in white hairs. These differences could indicate that the late-flowering variety might be attracting a different pollinator and may need to be considered as a separate species.

Photos

Early-flowering variety

Pterostylis sargentii
Tbd. (West Pingelly, WA, 03 / 08 / 2014)
Pterostylis sargentii
Tbd. (West Pingelly, WA, 03 / 08 / 2014)
Pterostylis sargentii
Tbd. (West Pingelly, WA, 17 / 08 / 2014)
Pterostylis sargentii
The colour of the flowers is generally quite variable and can range from green to dark brown. (Brookton, WA, 19 / 08 / 2016)
Pterostylis sargentii
Tbd. (West Pingelly, WA, 03 / 08 / 2014)
Pterostylis sargentii
Tbd. (Brookton, WA, 19 / 08 / 2016)
Pterostylis sargentii
Frog Greenhoods often grow in the company of other orchids such as the Little Pink Fairy Orchid (depicted here) and the Sugar Orchid. (Brookton, WA, 19 / 08 / 2016)

Late-flowering variety

Pterostylis sargentii
The flowers of the late-flowering variety look similar to those of early-flowering plants. (Jelcobine, WA, 18 / 09 / 2018)
Pterostylis sargentii
Close-up view of an individual flower of the late-flowering variety. (Jelcobine, WA, 18 / 09 / 2018)
Pterostylis sargentii
Close-up view of the hairy labellum of the late-flowering variety. (Jelcobine, WA, 18 / 09 / 2018)
Pterostylis sargentii
A comparison between the early (left) and late (right) flowering varieties reveals small differences in the structure of the labellum. (Jelcobine, WA, 03 / 08 / 2014 and 18 / 09 / 2018)

References