One of the key questions of our current research project is how, when, and why the ‘mimosa bush’ or ‘cassie’ tree got to Australia. Acacia farnesiana, also known as Vachellia farnesiana (if you agree with the splitting of the acacia genus) is presumed by many botanists to be native to a broad swath of the Americas, from Bolivia north to Texas. Yet it exists all around the tropical and subtropical world. The first British explorers of interior Australia found it growing all over the interior northern part of the continent. How did it get there, then? How long has it been there? The answer matters, because environmental managers these days want to know if a plant is ‘native’ or ‘alien’, as this has repercussions (for better or worse) on how they approach it.
One hypothesis is that the seeds, which according to the venerable book on seed dispersal by Henry Ridley could float in sea water for several weeks, got there on their own a long time ago. Or that Spanish and Portuguese colonisers of the New World (who certainly brought the plant to Europe quite early in their explorations for its value as a novelty, the delicate perfume of its flowers, or its utility as livestock fodder) brought the plant to places near Australia – Timor? Philippines? – and it floated from there. From its beachhead establishment, it would could been transported towards the interior, the outback, by those who consumed its seeds – perhaps emus, perhaps camels (once these had been introduced). Priya Rangan and I have written on the latter idea in a book chapter; with Dan Murphy and Karen Bell at the Royal Botanic Gardens (Melbourne) we are now using molecular techniques to further explore the different hypotheses. We’re also investigating Portuguese and Spanish archives.
Acacia farnesiana is also found in Fiji, for certain in northern Viti Levu and perhaps also around Labasa (on Vanua Levu) and on tiny Wakaya island, places less humid than Suva where I live. German botanist Berthold Seeman mentions the ‘scented’ acacia’s presence during his visit in 1860 as an ornamental restricted to foreign traders’ and missionaries’ gardens. Following the King’s Highway a few weeks ago, I found the scrubby, multi-branched plant from Rakiraki west to Lautoka. It grows individually, or in clusters, along the road, at the edges of sugar cane fields, and particularly in places livestock congregate.
Its local English name is said to be ‘Ellington’s curse’, a particularly evocative moniker for this thorny plant declared a noxious weed. Ellington is the name of a locality (and wharf) near Rakiraki, the northern tip of the island. The people I spoke to along the road called the plant ‘katta’ or ‘kataya’ (in Fiji-Hindi) or ‘walaulau’ (Fijian), names not mentioned in other databases. Smith’s Nova Flora Vitiensis mentions the Fijian names ‘vaivai vakavotona’ (‘vaivai’ is a name for many introduced Mimosaceae) and ‘oka’ and the Hindi name ‘ban baburi’ (probably meaning a jungle, i.e., wild, ‘babul’ which is a thorn tree known in India). Note, by the way, that Smith used ‘Ellington curse’ without the possessive, which may be the original version coined by some cattle station owner or government agricultural officer.
What’s in a name? Why does ‘Ellington’s curse’ appear over and over in botanical and weed websites, even though its use (I’m guessing) is limited to a few government land managers? In botanical databases, it generally suffices that one herbarium specimen somewhere has a particular local name noted on it, and that name is then repeated in each database that builds on the information in a previous collection. Authors like me writing about plants notice the evocative term (of course, in English) ‘Ellington curse’, unconsciously improve it by adding a possessive apostrophe-s, and highlight this term (a term most likely foreign to most of the sugar farmers, villagers, and livestock herders who encounter it most) in publications and websites. So as a result, there are over 3 million google hits for this name for a weedy plant on a corner of a small island in the Pacific. Go figure.
In any case, we still don’t know how Acacia farnesiana got to Australia, nor Fiji. While we shouldn’t ignore the likely role of European missionaries and traders (given that Seemann didn’t see the plant outside their gardens), here’s another hypothesis linked to the broader observation that a majority of roadside weeds in the islands are of tropical American origin: if Polynesians brought the sweet potato in ancient times from South America, why not also some farnesiana seeds?
I leave you with view of our well-travelled plant