Jacarandas: icons or pests?

By Australian Geographic 13 November 2018
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Jacaranda season is well and truly underway, and while you may think you know all there is to know about the iconic purple-flowered trees, there’s actually more to them than meets the eye.

JACARANDA SEASON is well and truly underway. At this time of year, people flock to ‘hotspots’ – that is, vistas lined with the iconic trees – while others might enjoy the individual, blooming brilliant tree outside their homes.

However you enjoy or have enjoyed jacaranda season: whether you once sat beneath the recently fallen jacaranda tree in the University of Sydney courtyard stressing over exams, or like to drive through the jacaranda tunnel of Sydney’s lower north shore, we all have a jacaranda story.

Despite our love affair with these purple beauties,  many people likely don’t realise that the jacaranda isn’t actually native to Australia. About 30 different species of tree belong to the Jacaranda genus, which has a broad range across southern America.

Jacaranda mimosifolia the species of jacaranda that Australians know and love – has a small native range in the north-west of Argentina and neighbouring Bolivia. There, it persists in a stressful, arid environment, making it well prepared for the Aussie climate.

How did Jacarandas arrive in Australia?

So how did they get here? According to Systemic Botanist from the Royal Botanic Garden Sydney, Dr Russell Barrett, it’s likely the first few jacarandas were propagated in Brisbane.

“We don’t have huge numbers of details about how it got here, but as far as we can tell the first seeds were brought in from Argentina to Brisbane. Shipping captains brought seeds to trade that they thought would be of interest, likely to make some cash on the side.

“It’s understood that a former director of the Brisbane City Botanical Garden, Walter Hill, bought some seeds off a shipping captain and planted them in 1864. And if you look at the current records on the Australasian Virtual Herbarium as to where they were recorded naturalised, you do get these span of dots centring out from Brisbane and they probably came to Sydney rapidly after,” says Russell.

Friend or foe?

Russell specialises in native Australian species, but he also keeps an eye on pests and weeds. Russell says new weed species are brought in to the National Herbarium of New South Wales at the Royal Botanic Garden Sydney about once a month. But, he says,  just because the jacaranda tree isn’t native, doesn’t necessarily mean it’s a pest or weed.

“They have the potential to become weeds, but that doesn’t happen often. And it’s definitely not considered to be a weed of economic importance. Instead, it’s something to be mindful of. For example, not planting it near waterways where its seeds can wash away.

“There are a few populations that have escaped into natural populations, but it’s typically a situation that can be controlled. In southern Africa, it’s a little bit of an issue because there are now a couple of million acres after birds distributed seed. But its impact is still minimal.”

However, some Australians have a different opinion, and not everyone is quite as fond of the jacaranda as others. For example, the flowers of a jacaranda can sometimes create ‘dirty laundry’ for an innocent neighbour.

But, in Russell’s opinion, these issues are relatively minor and mostly avoidable with good planning. And they definitely don’t outweigh the beauty of jacaranda season.