P. limnetes, the marsh leek-orchid, is known only from Rubicon with a conservation status of "critically endangered" nationally and "endangered" in Tasmania. Its location at Rubicon was known imprecisely until re-discovered following disturbance in its habitat in 2009. In general appearance, plants are similar to P. rostratum, which is widespread at Rubicon, but the flowering periods do not overlap. Collier (2011) reports a detailed morphological analysis that shows how the two species differ significantly on several characters, most obviously in the density of the flower spike and number of flowers.
Most P. limnetes plants were discovered in the years following an ecological burn in 2009: 14 in 2009, 33 more in 2010, and eight more in 2011. In 2009 and 2010 many flowers flowered and fruited successfully but in 2011 all the flower stems shrivelled before the flowers opened.
Because it was not feasible to burn again in 2012, we slashed a small area covering part of the known population of P. limnetes. The aim was to determine whether slashing is a suitable substitute method of disturbance and whether this disturbance would provide suitable conditions for plants to flower successfully.
The small area slashed led to significant interest from animals, with repeated damage to bracken markers of tagged plants, and little flowering in the year of the slash. We learnt the lesson that precious plants must be well protected from herbivores with cages in small areas of disturbance.
Despite the damage from herbivores in the area slashed in 2012, we found that the slashed area had a significantly higher rate of flowering and fruiting plants in 2013-14 compared with the nearby undisturbed area. Pleasingly, most plants were not badly affected by the shrivelling of flower stems that was evident in 2011 and 2012.
We burnt the P.limnetes area in late March 2015. 2015 turned out to be a very dry year and, perhaps due to this, only one P. limnetes plant produced a flower stem in December 2015. This was however a magnificent stem with 24 flowers.