A few species, such as the majestic spider orchid (Caladenia winfieldii) and the pink spider orchid (Caladenia harringtoniae), came to the attention of orchid enthusiast and Albany Advertiser editor Nathan Watson on a recent field trip.
The exact location of the rare orchids is a closely guarded secret by conservation biologists like WA Herbarium orchidaceae curator Andrew Brown.
The majestic spider orchid (Caladenia winfieldii)
Credit: Andrew Brown
Mr Brown and UWA Albany-based Winthrop Professor Stephen Hopper named the majestic spider orchid in 2001 after retired forest worker Harry Winfield who discovered the plant near Walpole.
Mr Brown is also a WA Native Orchid Study and Conservation Group founding member and the Department of Parks and Wildlife threatened flora coordinator, and oversees a citizen science project to collect information on threatened and vulnerable orchids.
The Adopt an Orchid program involves volunteers monitoring 38 priority species, including the majestic spider orchid, to determine conservation status and recovery plans to protect their population—which is limited to a single site east of Manjimup.
Mr Brown has spent more than 40 years studying WA's native orchids and says the scarce distribution of the majestic spider orchid is mysterious.
He says there are less than 100 majestic spider orchids known in the wild and although the main threats to the species survival include grazing by feral pigs and kangaroos, fire and dieback, the precise cause of its rarity is unknown.
A pink spider orchid. Credit: Nathan Watson
"It may be something to do with a pollinator or a rare fungus associated with the Mycorrhizas fungal relationship that supplies nutrients to the plants—but we do not really know," he says.
Mr Brown says feral pigs inhabit the same area and are known to dig up the specific root that stimulates the orchids' growth during a brief flowering season from October to November.
"When we first looked at that population it was badly damaged by pigs," he says.
Mr Brown says the majestic spider orchid's pollination process could also be a contributing factor to its limited number.
"We do not really know what the pollinator is—there is a bit of mystery about it," he says.
"Introduced bees could be a threat to native orchid populations as they remove pollen but do not deposit it."