3 May 2018

Jacaranda mimosifolia: a jewel in the Temperate House treasure trove

The ‘fern tree’ Jacaranda mimosifolia could hold the key to fighting drug resistant bacteria. Intern Jake Newitt tells us more.

By Jake Newitt

J. mimosifolia, Temperate House, RBG Kew

A journey of plant uses 

As an intern on the Plant and Fungal Trees of Life (PAFTOL) project, I have the chance to delve into some of the amazing plants that are cultivated here. I've found that there is no shortage of intriguing and useful qualities to learn about from these specimens. 
 
As part of a mini-series investigating my favourites, I’ve come across Jacaranda mimosifolia, a plant that you can see yourself in the recently renovated Temperate House. 

Vibrant flowers 

One of the common names for J. mimosifolia is the 'fern tree', so named after the shape of its leaves, which closely resemble that of the ancient group of plants called ferns. 
 
The leaves are arranged in a so-called 'pinnate' fashion and look a bit like feathers. 

This tree is from an entirely different group called 'angiosperms', more commonly known as flowering plants. 
 
Its vibrant flowers are one of the defining features of the fern tree. 
 
The spectacular purple bloom often occurs late spring to early summer and can last for up to two months. 
 
With a bit of luck, the specimen in the Temperate House should begin to flower by the end of May and can last for two months, so you should come down and see it when it does! 

A traditional healer 

Ultimately, it’s the exceptional properties of J.mimosifolia that impressed me. 
 
Firstly, the wood is prized by craftsmen for its quality. It is particularly malleable and easy to work with. 
 
Whitish/pale grey, it is relatively soft and knot free which makes it perfect for wood turning. This is the process by which bowls and other such products are formed by carving the wood whilst spinning it. 
 
The scientific community are rather excited by its remarkable history in treating microbial infections. 
 
Rooted in folklore, locals and traditional healers of South America have used the extract of the fern tree in this way for a long time. 
 
Scientists have since analysed the chemicals that can be found in it. Working with local healers and farmers when collecting the seed, they investigated its potential as a source of new medicine for fighting infection. 
 
The study conducted by Rojas et al. (2006) found that the water extract was capable of killing certain bacteria better than a well-known antibiotic – gentamycin sulphate. 
 
This could have a far-reaching impact today, whilst modern medicine faces a crisis in drug-resistant bacteria, and ‘superbugs’ like MRSA. 
 
Although it may take some years to identify and purify the medicine, many still bathe in leaf infusions of the fern tree to treat superficial wounds and acne. 

Rare and threatened 

The International Union for Conservation of Nature Red List of Threatened Species uses a set of criteria to evaluate the extinction risk of the world’s species - some of which we have in the Temperate House. 
 
J. mimosifolia is classified by the IUCN as 'vulnerable'. 
 
Although humans have cultivated it (largely as an ornamental tree), it is at a high risk of endangerment in the wild. 
 
At Kew, we feel strongly about conservation of plant and fungal diversity. 
 
Plants are not just valuable to us, they can play vital roles in their ecosystems. The large flowers of J. mimosifolia for example, attract key pollinators such as bees. 
 
This is vital in times of rapidly deteriorated bee populations.