Summer is never the time to get overly enthused about terrestrial orchids in the Anglesea district, although it is the time when the beautiful Rosy Hyacinth Orchid, Dipodium roseum, flowers throughout the area.
Rosy Hyacinth Orchid
After great displays of this orchid in summer 2016/2017 there have been very few this year, with many of the flower stems wilting in the dry conditions, or else being eaten by hungry kangaroos. I have not managed to find any of the White Hyacinth Orchids, Dipodium pardalinum, which has a much more localised habitat.
White Hyacinth Orchid
Horned Orchids, Orthoceras strictum, have also disappointed with very few flowering stems being observed. Again, often the ones we did locate had been eaten by kangaroos or wallabies.
The Large Tongue Orchid, Cryptostylis subulata, was coming into flower in mid-December but the dry conditions would not have been in its favour and I imagine many of the flowers would just not have developed.
Large Tongue Orchid
However there was one species that did us proud in early December, and that was the Elbow Orchid, Thynninorchis huntianus. Considered rare but often just overlooked because of its small size, slim flowers and its habit of growing under shrubs, we were thrilled to find flowers in good numbers in two sites we visited.
Elbow Orchid (Photo Colin Rowan)
It is such an interesting little orchid–leafless and relying entirely on fungi in the soil for its nutrients. The tubers often grow in deep leaf litter rather than in the soil itself, and this makes the populations very vulnerable to fire. It can take many years for the orchids to recolonise areas when the leaf litter has been removed by fire. This is true of the gravel pits in Mt Ingoldsby Rd where a lightning strike caused an intense fire in 2004. Prior to this time we had a very good population, but we have not managed to locate any since then.
This orchid has a most remarkable pollination strategy. It is pollinated by the male Thynnid wasp through sexual deception. Believing that the labellum is a female wasp, the male is attracted by the scent and then grasps the bottom of the hinged mobile labellum and attempts to fly away with ‘her’.
Close-up of Elbow Orchid (Photo Colin Rowan)
However the hinge is activated and the male wasp is grasped by the labellum and is swung back against the column where he becomes trapped. In endeavouring to free himself he either collects the pollen on his back or transfers what he has previously collected to the next flower. He eventually frees himself and keeps on exploring, repeating the process.
It is no wonder that we become fascinated with our terrestrial orchids!
All of these orchids are photographed and described in Orchids of the Anglesea District available from ANGAIR.