Mexican Marigold (Tagetes erecta syn T. patula), known as African or French Marigolds depending on the cultivar / chromosome count. An alien orange aster lovingly cultivated across continents and now a very occasional convulsive colonist of Port Phillip creeks and infrastructure.
[I won’t pretend to truly understand the state of the phylogenetics of Tagetes, so if you need to call this plant T. erecta or T. patula feel free to hold onto what you’ve got. The international authorities now seem to treat them as synonymous under T. erecta, so I will talk about Victorian records lodged as either species.]
A garden classic, Mexican Marigold has occasionally been found naturalised in New Zealand since the 1950s, and in scattered and possibly flaringly brief occurrences across southern, temperate Australia. It has shown up a handful of times in Victoria in naturalised circumstances: at Lara in the 1960s, and more recently on Moonee Ponds Creek and on the Yarra at Studley Park (of course). The most spectacular-sounding occurrence is or was a five km stretch of the Western Port Hwy south of Cranbourne, where the species was collected in 2011 having established hundreds of individuals along various median spaces—in pavement cracks, accumulated ‘soil’ detritus and so forth—in the years immediately following a major reconstruction of this roadway.
Somehow, I can find no photographs online of what must have been (or perhaps still is) a fantastically exotic inflorescence on normally forsaken medians.
The photographed plant(s) were found on Central Creek in Thomastown, a tributary of the Merri, in infrastructural space between highway ramps. Will this prove to be the fleeting refuge of a doomed plant regenerated temporarily from rafted garden waste, or the next superbloom on an invisible Melbourne road margin? The answer appears dependent upon environmental circumstance and the vigour of whichever cultivar is represented here. We’ll surely be back to track progress, and looking down Western Port way for the afterimage of that last roadside superbloom.