hi Tapirlord Isobel considers the species closer to J. subsecundus from material that Barb collected; however she mentioned that tepals are shorter than normal but that this may be because of abrasion due to the collected material being old. She also mentions that the 2 taxa subsecundus and filicaulis hybridise. I know close to nothing about the Genus and thus can't comment.
Hard to tell without pics of the basal leaves (for their colour) and longitudinal view of the pith in the culm/stem (continuous or interrupted in longitudinal view), @onetapir. And a habitat shot can also help with ID. It's not J. filicaulis (the inflorescence is much too big). Species with big inflorescences like this that might be in the Canberra region include J. alexandri, J. australis, J. flavidus, J. sarophorus.
@waltraud having asked Karen Wilson, this was my response. Going from here I'm thinking Juncus sp, what we can rule out is J.alexandri and probably J.australis. From the options above I reckon J.flavidus is the most likely option as I personally (perhaps incorrectly) associate J.sarophorus with the montane zone. The distribution of Juncus in the Canberra region is poorly known, and all 4 possibilities would be interesting so I would encourage the collection of material in a couple of months.
This material keys to Juncus subsecundus: pith interupted; stem striae 26; outer tepals 2.3 mm long and less than or equal to capsule; inner tepals 1.6 mm; anther 0.6 mm. With Schoenus apogon and Juncus articulatus.
@abread111 and @waltraud , My final comments on this sighting are as follows. I discussed the ID of J.subsecundus and we have come to the conclusion that the ID does not match the plant that is pictured here. I have no doubt regarding Isobel's ID, and that the specimens that Barbara collected are J.subsecundus so I suspect the logical conclusion here is that we are talking about two different groups of plants (Perhaps my GPS was inaccurate).
Karen and I have come to the conclusion that this specimen is J.sarophorus based on the size of teh infloresence and the length and shape of the tepals which rule out J.flavidus. I think we should give Karen's view a significant amount of weight given her expertise with this genus. The CNM ID will now reflect this advice.
thanks Tapirlord. Perhaps there's a need to search the surroundings for various Juncus species. The location of the sighting is upstream of the dam and from memory, there were Juncus plants perhaps various species during drought. I ignored them because I do not have the training to id and a botanist told me they are hard. GPS accuracy is a tricky thing - if the accuracy is around 5m the specimen may be out by around 10m due to the accumulation of errors from 2 devices.