Pope’s Glen Bushcare Group manages ranunculus by flooding.

By Alan Lane

When the Pope’s Glen Bushcare Group began removing the huge willows at the headwaters of Pope’s GlenCreek, Blackheath, they were shocked to see an immediate explosion of ranunculus in response to the improved light!  From the original scattered patches, the weed quickly established extensive monoculture carpets. (Fig. 1).  Controlling this by hand weeding was out of the question, so the group concentrated on weeding around their plantings. For the rest of the area, the group had to close their eyes and, as the Chinese saying goes, “wait for a solution.”

And the “solution” emerged quite unexpectedly when the group began building flow-control cells across the silt flat.  One purpose of these was to disperse storm water and so protect the silt flat from erosion.  A second purpose was to raise the water table, creating a permanent swamp.

However, it did not take long to observe another benefit of this “chain of ponds”. The higher water table suppressed ranunculus but simulated the native sedge, Carex gaudichaudiana. The increased water table shifted the environmental conditions in favour of the Carex so that it could now out-compete the ranunculus and largely replace it. (Fig. 2).

This project has been assisted by the New South Wales Government through its Environmental Trust.

 
Fig. 1: Dense carpet of ranunculus growing in response to increased light

Fig. 2: Carex out-competing ranunculus in response to higher water table.  Flow control cell indicated by row of stakes and logs.