South American Goldenrod (Solidago chilensis), a member of that prolific and striking lineage of predominantly Western Hemisphere asters, now established on suburban Melbourne streams.
Goldenrods were introduced to Australia through occasional use as a cultivated ornamental and cut flower; for instance, a specimen in the National Herbarium of Australia was donated from the garden at Government House in Canberra. Long-prized for their autumnal contribution to prairie-style gardens, some American species have also established in Europe and Asia alongside the Eurasian natives.
While Goldenrods began naturalising in NSW and South Australia in the 1930s and 1940s, species identifications have been confused by the complexity of this genus and a lack of familiarity and access to modern type material here. Recent reassessments of herbarium accessions by researchers from Monash University, and the University of Waterloo in Canada, have sorted out much of the confusion, although the national databases and state floras have not all updated to reflect their findings. One result of that work is that previous collections from WA, SA and Victoria were ID’d as S. chilensis.
In Victoria, Goldenrod specimens had been collected since the 1960s. Two species are now recognised to be present in this state: S. altissima, a hairy-stemmed North American plant that is in the S. canadensis complex, and S. chilensis, which has predominantly smooth stems and is seen here. To date, naturalised collections of S. altissima have occurred in far-flung regional towns (Boolarra, Korumburra, Wangaratta), presumably reflecting separate introductions from cultivated plants. By contrast, S. chilensis appears to be well-established and perpetuating itself within suburban reaches of the Yarra River and several tributaries.
The photographed plants were found along a 0.5 km stretch of degraded flood bank on the Darebin Creek in Thornbury; there are recent records of the species near the mouth of that creek, on the main channel of the Yarra north of Kew, and on Koonung Creek.