Twiggy Turnip (Brassica fruticulosa), an endemic mustard of the Western Mediterranean and recent introduction to Australia.
Unlike Mediterranean Turnip (Brassica tournefortii), whose interwar arrival posed a sudden menace to Australian wheat belts, Twiggy Turnip arrived almost entirely without notice or concern. The difference of course was in the geography of each incursion: while Med. Turnip was an immediate threat to grain yields, Twiggy Turnip has principally colonised urban wastes and road infrastructure.
Recorded once in 1930 on a railway siding in the Nullarbor, the species was collected on Sydney’s north shore in 1949 and at Keilor in 1950.
In NSW, at least one collector attributed its introduction to new cultivators; in Sicily this is the wild green Cavolicello, foraged from the shoulders of Mt. Etna, and the possibility that seeds were brought to Australia and cultivated cannot be discounted. However the attribution feels no less apocryphal than the familiar 19th c. stories that blamed so many weed invasions on individual gardeners, and does not explain how the plant arrived first on the Nullarbor and then simultaneously in Melbourne and Sydney at the end of the 1940s. It feels more likely that this was a contaminant of seed or materials, but the migrant garden was easy to blame.
Well-adapted to colonise disturbed and chemically suppressed ground, the plant’s presence in Victoria quickly expanded along the margins of roads, railways, fences and creeklines. These settings provide favourable geology in the form of crushed rock, construction sand and silty fill, suited to a plant that grows on exposed volcanic slopes in its home province.
In Melbourne, where the species is now ubiquitous, the yellow florets of Twiggy Turnip make such an untidiness of the city’s margins it is surprising to find little evidence of public complaint at its arrival. A post-WW2 urban weed, it made an end run around the historical sources and journalist interest in problem plants on which this history has so far relied, slipping past us through the cacophony of modern times!