Stinging Trees

When I was 12, I fell into a clump of young shrubs that looked totally innocuous. The very large heart shaped leaves looked soft and tender. The sting they inflicted was so severe I was in bed for three days. It took me months before the tingly sensation left. I had been stung by juvenile - the worst kind - giant stinging trees.

The pain can be so bad that it induces vomiting, and some of the literature suggests the sting can be fatal.

Arguably the most painful plant in the world, the giant stinging tree grows in the rainforests of coastal Queensland and New South Wales, eastern Australia. They like to grow in areas near river courses, especially in clear or disturbed areas. They are supposed to gow to about 40 metres high, but the largest ones at Barrington Tops National Park grow to about 20 metres high, with a trunk about 0.5 metres in diameter. The bark is light in colour, and older trees, you can touch the trunk without being stung.

The leaves, however, are covered in silica - glass - spikes, and when touched causes immediate pain which can last for days. The young trees grow rapidly. They are a rainforest pioneer  species. The wood is very soft and if a tree is felled it will rot away within months.

The leaves of the tree are heart shaped and usually have large gaping holes in them caused by beetles. The leaves are covered in dense hairs which the tree uses to sting it predators. Each tiny silicon hair contains neurotoxin and on touch they break off and inject the venom. Even dead leaves can sting. My wife once stepped on an almost completely rotted leaf at the bottom of a river bed, and was severely stung by the dead leaf. There are reports that the stinging hairs can be potent for decades after the leaf has died. 

There are only male flowers or female flowers on a giant stinging tree. Giant stinging trees are easily recognised from the six other species of Australian stinging tree. For starters, they are big. The tree is easily identified by its large, heart shaped leaves, covered with dense hairs. The leaves are often full of holes; this is caused by a beetle which eats the leaves. Flowers are yellow-green, and the fruit is a small nut on an expanded fleshy stalk resembling a mulberry in colour and texture. These stalks are an important winter fruit for the Green Catbird and the Regent Bowerbird.

Stinging trees play an important part in the ecology of a rainforest. Many native Australian animals, birds and insects are not bothered by the sting, and happily devour the leaves and fruit. Red legged pademelons - small fat wallabies about the size of a small dog, reportedly love eating the leaves. They are certainly endemic in locations where stinging tress grow.

You need thick gloves to stop a stinging tree. Cotton or denim is not sufficient to ward off a sting. The silicon hairs penetrate your skin, and then break off. They're so tiny, that often the skin will close over the hairs. So sometimes, once you've been stung, you can't remove the stinging hairs.  What's worse is that you can get stung even after the leaf is dead.

The neurotoxin is very stable. Experiments have been done with hairs that were collected nearly a century ago, and they can still cause pain. The reaction depends on what species of animal gets stung, and how many hairs get stuck in the skin. But humans feel something between mild irritation and intense pain and death. The pain comes immediately after touching the plant, and it gradually increases to a peak after about 20-30 minutes. The Dutch Botanist H. J. Winkler made the only official recording of Death By Stinging Tree, for a human. It was in New Guinea, back in the early 1920s.

But you can suffer even if you don't touch the plant. The plants continuously shed their stinging hairs. Stay close to the stinging trees for more than an hour, and you can get an allergic reaction - intensely painful and with continuous bouts of sneezing. You can even get nose bleeds from these silicon hairs floating in the air.

There are two strange things about these stinging trees. First, these stinging trees are harmless to many native Australian species, but very nasty to introduced species such as humans, horses and dogs.

The second thing is according to some articles, the pain is real and intense, but your body does not suffer any damage. Fire and snake bites cause pain, and they damage you as well. But it seems that the pain from this tree could be the only pain that is not related to any damage.