European Sea Rocket (Cakile maritima), a specialist of the coastal strand and a ballast weed delivered to Western Australia in the 1890s and to Victoria c. 1922 when it apparently landed in the vicinity of Beaumaris.
European Sea Rocket is botanically famous (meaning not at all famous) for having progressively replaced American Sea Rocket (Cakile edentula) across much of the Australian coastline over the course of the last century. American Sea Rocket arrived first, recorded in SA from the 1860s, and from Phillip Island in 1863 by von Mueller, who wrote that it had been known there twenty years (ie. from the 1840s). Eventually extending from Esperance Bay in WA to the mid-Queensland coast at Mackay, the American rocket was then replaced by this European species across that range save for limited remaining footholds in Northern NSW, Queensland and Tasmania.
It has been speculated that both species were introduced and spread around the country in ships’ ballast, possibly by grain carriers calling at various smaller ports. However the mechanism by which C. maritima succeeded and the colonies of C. edentula faded away so rapidly is not known. Although ALA has various later observation reports, likely misidentified, Cousins et al (2013) peg the last record of American Sea Rocket in Victoria to 1986 (in far eastern Gippsland). It is also notable that there is some suggestion of several Australian populations of C. maritima with different European origins, based on their morphological distinctions.
European Sea Rocket is a relatively benign intruder, invading a coastal niche largely unoccupied by indigenous Australian species both on Melbourne’s urban beaches and across the wider swathe of Australia’s temperate and sub-tropical coastline. As with many salt-tolerant coastal species, the plant can also occasionally be found colonising saline inland soils and wetlands. To end on a rare culinary note, Sea Rocket’s somewhat tough and green-tasting leaves have a strong peppery mustard flavour befitting its common name and relationship to other Brassicas.