For many years I have been photographing the Spotted Sun Orchid (Thelymitra ixioides) on our property. I was aware that there was a variation in colour and often in the location of the spots. Recently, with the help of ‘Bush Gems’ an excellent reference to Victoria’s orchids by Gary Backhouse, I realise there are two species of Sun Orchids located in our region which have spots – the second species being Rush-leaf Sun Orchid Thelymitra juncifolia). Backhouse mentions that Thelymitra jucifolia was first described in 1840 but due to the similarities this species has with Thelymitra ixioides, it is often overlooked.
Reading through the descriptions of both species, I can see why the Rush-Leaf Sun-Orchid is often confused with and identified as the Spotted Sun-Orchid. It seems the distinctions are quite fine. Backhouse says:
- Rush-leaf Sun-Orchids have fewer yellow glands on the column
- Spotted Sun-Orchids are larger
- Spotted Sun-Orchids have well-defined spots while Rush-leaf Sun-Orchids have more blurred edges (although both can have few spots or no spots)
- The tufts on the lateral lobes are generally sparser on the Rush-leaf Sun-orhid
- As the flowers of both species grow, the number of yellow glands increases, so this is not a reliable identifier on its own.
As today was blustery and I could not go out and try to photograph the opening sun-orchids, I decided to check back through photograps I had taken in previous years. I think we have both species, but getting to the point of saying “This is definitely a Rush-leaf Sun-Orchid and this is definitely a Spotted Sun-Orchid is tricky. More photographs are required.
Just to add to the confusion, in her text ‘Flora of the Otway Plain and Ranges 1” – one of my favourite references to identify plants – Enid Mayfield calls Thelymitra juncifolia the Large-spotted Sun-Orchid.
For now, I am just going to post a gallery of photographs I have taken on our property of Sun-orchids with spots. I will continue to try to distinguish between these species. If you have any suggestions for further reading on this topic I would be keen to hear about it.