Azolla (A pinnata), a floating aquatic fern, has been followed in Sydney Olympic Park (Australia) over the past two decades. Although a native fern, it can reach weed or problem proportion especially in urban situations. It’s coverage, growth and control have been closely studied but no set environmental cues or water quality parameters could be used as a guide for predicting its coverage and growth patterns. Whilst a sudden drop in ambient temperature by about 10oC almost overnight smothered this fern from open water areas but at the same time the pockets that were sheltered by aquatic macrophytes or other objects, such pockets remained significantly unaffected (p<0.001; F= 19.95). If in one wetland it showed an annual cycle of growth and decay whereas in another wetland it did not decay unless a severely cold front was present. Various control measures have also been trialled and no single method has yielded satisfactory results except a combination. By far, aerial application of 8% saline water on the plants have resulted in statistically significant dieback but without repeat applications, full control was not possible. The timing of appearance of Azolla in a wetland cannot be envisaged but any success in control measures will rely on early interventions such as harvesting or corralling.