PterostylisListing Statement for falcataPterostylis falcata (sickle greenhood) sickle greenhood T A S M A N I A N T H R E A T E N E D S P E C I E S L I S T I N G S T A T E M E N T Image by Marie Macdermott, Tasmanian Herbarium Scientific name: Pterostylis falcata R.S.Rogers, Proc. Roy. Soc. Vict. ser.2, 28(1): 106, t.9 (1915) Common name: sickle greenhood (Wapstra et al. 2005) Group: vascular plant, monocotyledon, family Orchidaceae Status: Threatened Species Protection Act 1995: endangered Environment Protection and Biodiversity Conservation Act 1999: Not listed Distribution: Endemic status: not endemic to Tasmania Tasmanian NRM Regions: North Figure 1. Distribution of Pterostylis falcata in Tasmania, Plate 1. Pterostylis falcata (ex NSW) (image by Marie showing Natural Resource Management regions Macdermott, Tasmanian Herbarium) 1 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis falcata (sickle greenhood) SUMMARY: Pterostylis falcata (sickle greenhood) Pterostylis falcata is a summer-flowering is a terrestrial orchid that in Tasmania has been greenhood (Jones et al. 1999). On the mainland, recorded from only 3 or 4 localities in the north flowering is between September and January of the State, presumably from moist to wet (Jones 2006) but herbarium records from forests on fertile substrates. The species has not Tasmania suggest a peak in Tasmania in late been recorded since 1972 and the precise December into January (Wapstra et al. 2012). location of sites is unknown. Given the limited collections and time since the last recording, the The response of Pterostylis falcata to disturbance total population in Tasmania is presumed to be is largely undocumented but its preferred small, with fewer than 250 mature plants, and habitats have relatively low fire frequencies. A likely to occupy less than 5 ha. Loss of habitat too frequent and/or high intensity fire regime is through historical clearing may explain the likely to be detrimental. Occurrences appear to fragmented distribution of the species in be highly localised meaning that some forms of Tasmania. While a better understanding of the disturbance such as intensive grazing and soil distribution and needs of the species is required compaction are likely to be unfavourable. to guide management, the most important known need of the species is to prevent Survey techniques destruction and degradation of potential habitat Surveys should be conducted during the in the general vicinity of recorded sites. species’ peak flowering period, which is identified as late December into January IDENTIFICATION AND ECOLOGY (Wapstra et al. 2012). Detecting the rosette of leaves prior to flowering amongst dense shrubs Pterostylis falcata is a single-flowered tall herb in a is likely to be very difficult. Detection will be group of plants known as greenhoods. The most successful when flowers are fully open name greenhood arises because the dorsal sepal but older flowers may still be identifiable, and petals are united to form a predominantly extending the survey window for 1 to 2 weeks, green hood-like structure that dominates the depending on seasonal and local conditions. flower. When triggered by touch, the labellum Fresh plants and/or high quality digital images flips inwards towards the column, trapping any (showing scale) are recommended to allow insect inside the flower, thereby aiding expert identification of plants suspected to be pollination as the insect struggles to escape. Pterostylis falcata. Greenhoods are deciduous terrestrial herbs that have fleshy tubers, which are replaced annually. Description At some stage in their life cycle all greenhoods produce a rosette of leaves. Plants that develop or do not develop flowers have similar rosettes of basal leaves. They have Pterostylis falcata reproduces from seed but the 4 to 7 bright green leaves that form a rosette, species also forms clonal colonies. The plants which in flowering plants encircle the base of flower for a short period each year (in the order the scape or are scattered up the scape. The of weeks) before being fertilised though old leaves are subsessile with an ovate-lanceolate flowers often persist on the stalk for many lamina and entire margins. They are 30 to weeks. Seed production and release is likely to 80 mm long and 14 to 25 mm wide. The fleshy follow shortly after fertilisation. Natural and smooth flowering scape is 15 to 30 cm tall. mortality in all phases of its above-ground The inflorescence is a solitary green and white existence is expected to be low and caused by flower that is held erect and is sometimes semi- grazing (by native marsupials, or stock, if nodding. It is 60 to 80 mm long and 20 to present), drought-stress (in periods of extreme 24 mm wide in plants from mainland Australia, drought only) and fire. However, the species is though Tasmanian plants tend to be in the 45 likely to survive into subsequent years, re- to 65 mm range. The galea (hood) has an apex establishing from the underground tuber (Jones that is curved forward like a sickle and is usually et al. 1999). held horizontally, the dorsal sepal being much longer than the petals. The dorsal sepal is 60 to 2 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis falcata (sickle greenhood) 75 mm long and 18 to 24 mm wide, ending in a back (recurved). The species is most similar to long tapered point. The petals are shallowly Pterostylis furcata which has smaller flowers (up curved and pointed and are 45 to 55 mm long to 40 mm long), the flower is held obliquely and 7 to 9 mm wide. The tips of the dorsal erect, and the free points of the lateral sepals sepal and petals are loosely joined. The lateral are much shorter (22 to 30 mm long). sepals very loosely embrace the galea leaving a wide lateral gap. The sinus between the lateral DISTRIBUTION AND HABITAT sepals is deeply notched and slightly bulging. The free points of the lateral sepals are 30 to Pterostylis falcata occurs in Victoria, South 40 mm long and are held erect above the galea Australia, New South Wales, Queensland and or are recurved. The labellum protrudes from the Australian Capital Territory (Jones 1998, the sinus, even when reflexed. It is curved, dark Jones et al. 1999). In Tasmania, the species has green to brown, and narrowly ovate to been recorded around Exeter, Mount Barrow, lanceolate, 25 to 34 mm long and 3 to 4 mm and Ben Lomond (Table 1, Figure 1). Habitat wide. The column is 20 to 23 mm long. on the mainland is moist to wet areas in open forests and shrubland, especially near streams [description based on Jones 1998, Jones et al. and swamps, in clay and peaty loams, from 1999, Jones 2006] lowland to 1,000 m elevation (Jones et al. 1999). The habitat in Tasmania can only be guessed at Confusing species based on locality information, but is suspected In Tasmania, there has long been confusion to be moist to wet forests on fertile substrates. surrounding the identification of specimens resembling Pterostylis falcata and Pterostylis furcata, POPULATION PARAMETERS exacerbated by the recent description of In Tasmania, Pterostylis falcata has been recorded Pterostylis lustra (Jones 2006), a species confused from 3 or 4 subpopulations (Table 1), though with Pterostylis falcata, and the recognition that location details are imprecise, and the species Pterostylis Xingens (a hybrid entity between has not been formally recorded for many Pterostylis falcata and Pterostylis nutans) does occur decades. The extent of occurrence of the in northern Tasmania (Jones 2006). The image species is estimated to be in the order of ascribed to Pterostylis falcata in the Orchids of 2 340 km , and the linear range about 60 to Tasmania (Jones et al. 1999) is almost certainly 70 km. The area of occupancy is unknown, but an image of Pterostylis lustra. Clements (1989) given the time since the species has been seen treated Pterostylis falcata and Pterostylis furcata as and the paucity of records, is presumed to be synonymous but Jones (1998) resurrected the less than 1 ha. two entities for Tasmania, recognising Pterostylis furcata as endemic and Pterostylis falcata as Jones (2006) notes that the species is often widespread on the mainland but uncommon in common on mainland Australia. However, as Tasmania. Jones et al. (1999) noted that many the species has not been recorded often and records of Pterostylis falcata are not backed up by not for many decades, it is presumed that herbarium specimens and have probably arisen Tasmanian subpopulations are small, making it from confusion with the smaller and more reasonable to assume that the total population widespread Pterostylis furcata. does not exceed 250 mature individuals. The likelihood of further subpopulations being Pterostylis falcata is recognised as a summer- detected is relatively high, based simply on the flowering species with large green and white extent of potential habitat meaning that range flowers that are 60 to 80 mm long (by far the extensions and infillings are likely. The success largest of all Tasmanian greenhood species), of extension surveys is often associated with with a prominent sickle-shaped galea that is surveys that radiate out from known sites. usually held horizontally, a long protruding However, the precise location of Pterostylis labellum, and long (30 to 40 mm) free points falcata in Tasmania is unknown so that on the lateral sepals that are sometimes swept discovery is likely to be serendipitous. 3 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis falcata (sickle greenhood) Table 1.