Updated: May 17, 2021
Many people would not think of looking for orchids in autumn, but in the Greater Adelaide region we have three orchid species flowering at this time of the year, with many winter orchids not far behind. By late April, one of South Australia’s most attractive autumn orchid, the Fringed Hare Orchid, Leporella fimbriata will be in the middle of its flowering time.
This enchanting orchid is easily identified by its reddish-purple-green flower with its two upright petals and broad fringed labellum giving it a ballerina like appearance (or is it looking like a hold up?). It grows up to 25 cm tall on a slender stem with 2 (or sometimes 3 flowers). A feature of autumn orchids is the appearance of the leaf toward the end of flowering and after flowering. The leaf is an attractive grey green with a distinctive red stripe. Ovate in shape it hugs the ground.
This orchid is primarily found in woodland, heath or scrub and most often found growing in sandy or sandy loam soil. However, at higher elevations, it can be found on gravelly soil ridges.
Leporella fimbriata is a fascinating species as it has a strange reproductive strategy – the pollinator is an ant! This is unique as ants are rarely pollinators. There have been various theories proposed as to why they are not pollinators but none have been confirmed. So how does it come about? The pollination strategy used by L. fimbriata is that of pseudo-copulation. The orchid produces pheromones (scent) with which to attract its pollinator. In this instance the pollinator is the hapless winged male of Myrmecia urens (Bull Ant) thinking it has found a virgin queen ant to mate with.
Leporella fimbriata with pollinator Myrmecia urens. Orchid pollen is contained in sacs called pollinia, as seen on this ant. (c) Lyn Edwards
Because the timing has to be right – the emergence of the ant and the opening of the flower – it is an event that has not always been observed even though both species are relatively common. This unusual strategy was only discovered in 1979 due to the work of Bob Bates, orchidologist and citizen scientist. In 1984 researchers confirmed this discovery.
Leporella fimbriata leaves, after flowering, growing close to an ants nest
Who knows what other information citizen scientists can discover about the relationship between these two species, or for that matter the relationship between other flowers and their pollinators. There is so much still to be discovered. The City Nature Challenge is a fantastic opportunity to collect valuable data by taking photographs of both the orchid and ant and then upload it to iNaturalist. At the same time, keep your eyes peeled for any other orchids that may be starting to emerge.
Thank you Lyn Edwards for supplying the image of the orchid and pollinator.
Video of the ants pollinating the orchid (c) Mark Brundett