29 May 2019

Strangler figs: killers or bodyguards?

Strangler figs engulf trees and create mythical-like forests. Not just a 'tree-killer', they provide food and protection within their habitats. Grace Brewer, Research Assistant at Kew, tells us more.

Strangler fig, Palm House, Ellen McHale/RBG Kew

Not just the stuff of fiction 

Deep, dark forests can take on sinister shapes. Plants all fight for light, and only the fittest can survive.

From Hogwarts’ Forbidden Forest to Tolkien’s Ent creatures, plants that have striking adaptations to survive in harsh environments have inspired generations of writers.

None more so than the strangler fig - the common name for a number of tropical and subtropical plant species which share the characteristic of ‘strangling’ their host tree.

Birth of a 'tree-killer'

Strangler figs begin life as a sticky seed on a tree branch high up in the canopy and are usually left there by an animal.

As the young strangler fig grows, long roots grow down along the trunk of the host tree, eventually completely engulfing the host tree trunk. Once these roots reach the ground, they enter the soil. At the same time, the strangler fig grows leaves.

The weeping fig (Ficus benjamina) develops roots from their branches and these grow directly down towards the ground.

In this species of strangler fig, once these roots reach the ground, they grow outwards in the soil and thicken to produce trunk-like structures. This can result in large patches of strangler fig forest all originating from one plant.

The growth process of strangler figs can be murderous, leading to the death of its host, and earning it the Spanish nickname, ‘matapalo’ (tree-killer). The roots constrict the trunk of the host tree and surround the host tree roots, cutting off the nutrient and water supply. Its thick fig foliage high up in the canopy can also steal sunlight.

Strangler fig, Palm House
Strangler fig, Palm House, Ellen McHale/RBG Kew

A misunderstood bodyguard?

Strangler figs are not just destructive parasites; they are very ecologically important in tropical areas.

The hollow centre of strangler figs provides habitats for a number of animals including bats and birds. They are also known as ‘keystone species’, as their fruits provide an important source of food to a variety of animals.

Researchers found that strangler figs may support their hosts during severe storms. In Lamington National Park, Queensland, Australia, following a cyclone, there were more standing trees with attached strangler figs than uprooted trees with attached strangler figs.

The aerial roots of strangler figs may attach to surrounding vegetation on the ground, stabilising the host plant and making it less likely to become uprooted. The leaves of the fig may also help shield from wind by closing up the forest canopy. Finally, the root networks surrounding the host tree trunks may provide a scaffold and support the trunk.

Strangler figs at Kew 

Any plant-lover cannot help but be inspired by the wonderfully winding shapes and sturdy structures exhibited by the strangler fig. 

It is no surprise to know that they are regarded by some religions as sacred - it is said that Buddha once meditated beneath one.

Come see them for yourself at the Palm House at Kew - and take a pen and paper with you, for who knows when inspiration may strike.

Strangler fig, Palm house
Strangler fig, Palm house, Ellen McHale/RBG Kew

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