Rhizanthella slateri (Rupp) M.A. Clem. & Cribb in the Great Lakes local government area - profile

Indicative distribution

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Key:

known

predicted

The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas. ( click here to see geographic restrictions). The information presented in this map is only indicative and may contain errors and omissions.

Scientific name: Rhizanthella slateri - endangered population

Conservation status in NSW: Endangered Population

Commonwealth status: Not listed

Gazetted date: 08 Dec 2006

Profile last updated: 07 Jun 2022

Description

Rhizanthella slateri is an endemic Australian orchid that is a terrestrial saprophyte (i.e. it derives its nourishment from dead or decaying organic matter). It has a fleshy underground stem to at least 15 cm long and 1.5cm in diameter. The bracts are prominent, often branching, fleshy, whitish and overlapping. The flower heads mature below the soil surface but sometimes may extend 2 cm above the ground, and are about 2 cm in diameter. The receptacle has up to 18 whitish triangular bracts about 8 mm long and has up to 30 flowers which are tubular and purplish.

Biologically, Rhizanthella slateri is of significant conservation value because of its unusual life cycle. It is one of only three Australian species, and a small number of species worldwide, that are capable of completing their entire lifecycle underground. Subterranean flowering plants such as these are extremely unusual and are of great scientific interest to biologists all over the world.

Distribution

Rhizanthella slateri is restricted to New South Wales where it is currently known from 14 populations including Bulahdelah, the Watagan Mountains, the Blue Mountains, Wiseman's Ferry area, Agnes Banks and near Nowra. The Rhizanthella slateri population in the Great Lakes Local Government Area (LGA) occurs at the known northern limit of the species' range and is disjunct from other known populations of the species.

Surveys conducted between 2002 and 2005 near Bulahdelah (within the Great Lakes LGA) identified approximately 75 flowerheads, more than ten times the number observed at any other site. The Rhizanthella slateri population in the Great Lakes LGA is thus likely to be the largest and most extensive known population of the species. Other known populations of Rhizanthella slateri are fragmented and highly disjunct, comprising isolated individuals or small clusters of plants.

Habitat and ecology

Rhizanthella slateri flowers from September to November.
Apparently prefers sclerophyll forest with a reasonably deep layer of organic litter although little else is know about the habitat of this species.
The ecology of Rhizanthella slateri is poorly known given that it grows almost completely below the soil surface, with flower heads being the only part of the plant that can occur above ground. Therefore plants are usually located only when the soil is disturbed.

Regional distribution and habitat

Click on a region below to view detailed distribution, habitat and vegetation information.

NSW North Coast

Threats

The Rhizanthella slateri population in the Great Lakes LGA is threatened by a proposal to construct a road through the population. The proposal will result in the direct removal of 4% of the known population and other individuals as yet undetected may become exposed after clearing or excavation works.
A further 34% of the known population is indirectly threatened by altered drainage and changes in soil moisture, and by weed invasion associated with the road.
The proposed road will remove 9% of known habitat and 29% of potential habitat for the species, fragmenting the population and potentially disrupting pollination and seed dispersal.
Orchid collectors represent a further threat to the species due to its very unusual growth form and extreme rarity, and the publicity associated with the Bulahdelah site.
The Rhizanthella slateri population in the Great Lakes LGA may also be threatened by environmental and demographic stochasticity due to its restricted area and small size.

Recovery strategies

A Saving Our Species conservation project is currently being developed for this species and will be available soon. For information on how you can contribute to this species' recovery, see the Activities to assist this species section below.

Activities to assist this species

Avoid further clearing and degradation of habitat.
Control invasive weeds which threaten to degrade the habitat.
Support ongoing ecological, biological and genetic research on the species.
Investigate the potenial construction of fencing to restrict access.
Raise awareness about the damage caused by illegal orchid collection.
Support existing translocation programs.

Information sources

Bernhardt, P. (1993) Rhizanthella. Pp 219 in Harden, G. (ed.) Flora of New South Wales. Volume 4. New South Wales University Press, Kensington.
Jones D.L. (2006) A complete guide to native orchids of Australia including the Island Territories. (Reed New Holland, Sydney)
Roads and Traffic Authority (2004) Bulahdelah Upgrading the Pacific Highway, Environmental Impact Statement. Technical Paper 7, Ecological Assessment and Species Impact Statement. (Roads and Traffic Authority of NSW)