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Conserving the terrestrial orchids of NSW

Diuris callitrophila
Diuris callitrophila
Photo: Karen Sommerville
 
    Pterostylis sp. 'Botany Bay'
Pterostylis sp. ‘Botany Bay’
Photo: Karen Sommerville
 
Diuris venosa - pollinated & bagged
Diuris venosa – pollinated and bagged
Photo: Karen Sommerville
 
    Diuris ochroma
Diuris ochroma
Photo: Karen Sommerville

The future of NSW’s beautiful terrestrial orchids is being secured through an on-going program at The Australian Botanic Garden Mount Annan.

Staff at The Australian Botanic Garden are collecting seed for as many threatened orchid species as possible. This sometimes involves hand-pollination and bagging flowers in the field, which ensures that seed is set and is not hybrid in origin ­– that is, not pollinated by a different species. Bagging also keeps seeds safe from hungry insects or other animals.

Three endangered species recently collected in this way are Diuris callitrophila and Diuris flavescens from NSW, and Pterostylis sp. Botany Bay from Kamay Botany Bay National Park. A good seed collection of all three species is now safely stored in the NSW Seedbank, along with other threatened species such as Caladenia arenaria from Buckingbong State Forest, Diuris venosa from Barrington Tops National Park and Diuris ochroma from Kosciusko National Park.

To germinate in the wild, orchid seeds need a fungal symbiont – a fungus that lives on the plant, while providing nutrients in return. Collectors therefore take soil samples from the base of the orchid while taking seed pods, and later germinate a few seeds in that soil.

The fungi in the soil invade the seeds, providing them with nutrients needed for germination. When a shoot emerges, the seedling is placed on a jelly-like substance called agar, which encourages fungal growth while preventing the growth of contaminating bacteria. After further growth, the fungus is tested to find out whether it is the correct strain for the orchid’s germination. If so, it is stored, ensuring that the conservation collection contains both the seed and the means to germinate it.

This work has been funded to date by the Hermon Slade Foundation, the Slade Orchid Fund, and the Millennium Seed Bank Project.