We investigate the utility of using historical data sources to track changes in flowering time of coastal species in south-eastern Australia in response to recent climate warming. Studies of this nature in the southern hemisphere are rare, mainly because of a paucity of long-term data sources. Despite this, we found there is considerable potential to utilise existing data sourced from herbaria collections and field naturalists’ notes and diaries to identify native plant species suitable as biological indicators of climate change. Of 101 candidate species investigated in the present study, eight were identified as showing a general trend towards earlier flowering over time, indicating a correlation with increasing temperatures. There was some evidence to suggest that species which flower in spring and summer may be more sensitive to changes in temperature. There was a high level of uncertainty regarding the detection of trends, which was a function of the accessibility, abundance and accuracy of the various data sources. However, this uncertainty could be resolved in future studies by combining the datasets from the present study with field monitoring of phenological cycles in climatically different locations. Data held by community groups could be made more accessible if there was a concerted effort to fund collation and digitisation of these records. This might best be achieved by working with community groups, and facilitated through the recent establishment of a community phenological observation database in Australia.