Once thought to be too difficult to remove from our river systems, the South East Regional Centre for Urban Landcare (SERCUL) has been eradicating hydroctyle in the Canning River as part of the Swan Canning River Recovery Stage 3.
Hydrocotyle ranunculoides, sometimes called ‘floating pennywort’, was introduced into Perth’s river systems after being introduced to the region as an aquarium plant.
This invasive species has ‘declared pest’ status in Western Australia, due to its ability to double in mass every 3-7 days, reproducing both vegetatively (rapidly growing) and through seed dispersal.
Hydrocotyle can form dense mats from bank to bank, disrupting the natural ecology, displacing native vegetation, contributing to deoxygenation and fish kills, and even impacting recreational use of the river.
The team at SERCUL developed an eradication and monitoring program that proved eternal vigilance is the most effective management strategy, as even a small amount of hydrocotyle hiding among other plant life during a weeding activity can start the whole cycle anew.
After showing significant success with their management strategy at a Water Corporation project (Mills Street Drain), SERCUL have been managing this weed across 24 hectares of the Canning River since 2015 as part of the Swan Canning River Recovery (SCRR).
This funding has provided a consistent approach to tackling hydrocotyle across an area involving a number of land managers,and has been effective at landscape scale.
However, while the program’s success so far means that hand-removal is now the most effective means of direct control, including the removal of other weeds it can hide in, it is the system for mapping and monitoring that remains crucial as the goal of eradicating the pest draws closer.
The Swan Canning River Recovery Stage 3 is managed by Perth NRM through funding from the Australian Government.
Image supplied by SERCUL.