The gympie-gympie (Dendrocnide moroides) is part of the Urticaceae nettle family, which also includes the common stinging nettle (Urtica dioica). Also known as the stinging bush, gympie stinger or mulberry-leaved stringer, most experts regard it as the most painful plant in the world to come into contact with.
Thankfully, this species is mostly confined to the tropical rainforests of northeastern Australia, so you aren't likely to come across it in your backyard. However, knowing how to identify the plant could save you from getting a very nasty surprise if you are exploring the region.
Which Part of the Gympie-Gympie Is Toxic?
The trichomes are responsible for the gympie-gympie's potent sting. These stiff, hollow, fine epidermal hairs made from silica cover the entire plant. When they enter the skin, even with just the lightest touch, the structurally weak part of the hair near the tip breaks off, injecting venom.
The trichomes can stay in the skin for up to a year. Because the plant sheds them into the air, they can also be inhaled.
Most mammals suffer severe ill effects from the gympie-gympie sting. Although there has only been one recorded human death, horses and dogs have succumbed to the ferocity of this plant's toxins and died. However, some animals native to the rainforests can touch and even eat the plant without having any problems. These include various beetles, moths, and pademelons (a rainforest kangaroo). Scientists believe that over time they have adapted to tolerate the toxins.
How to Identify Gympie-Gympie
The gympie-gympie is a soft-wooded, straggly perennial shrub with large, broad, heart-shaped, toothed foliage. Because of the density of the stinging hairs that cover the leaves, they have a furry appearance. All parts of the plant have a covering of stinging hairs, not just the leaves.
The shrub can grow to reach over 15 feet in height but commonly only grows to be around 3 feet tall—the perfect height for catching the ankles of unsuspecting forestry workers or those exploring the plant's natural rainforest habitats. This is why they are also sometimes referred to as "ankle-biters."
Clusters of small, insignificant flowers grow at the end of the flower stalks throughout the year, but mostly in summer. They then develop into purple-red, fleshy, shiny, seed-like fruit (referred to as achenes).
Plants That Look Similar to Gympie-Gympie
A few other stinging tree species in the Urticaceae family are similar to the gympie-gympie, but their stings are not quite as potent, and they tend to grow taller.
The one most commonly mistaken for Dendrocnide moroides is Dendrocnide cordifolia. It looks similar, and it grows in the same tropical regions of northeastern Australia. Although the sting of the D. cordifolia may not be as strong as that of the gympie-gympie, it can still inflict intense pain that can linger for weeks.
The fruit of the gympie-gympie is purple-red and grows on long stems, but the fruit of D. cordifolia is green and appears on short stems. Plus, the gympie-gympie leaf petiole (stalk) is attached to the underside of the foliage rather than connecting to the notch on the leaf edge like D. cordifolia.
Where Does Gympie-Gympie Grow?
Primarily found in tropical areas of northeastern Australia, gympie-gympie grows prolifically in rainforest clearings and along creek lines. These plants prefer moist, sheltered areas where the canopy is clear enough for them to get ample sunlight. Birds visiting these parts then disperse the seeds.
How to Get Rid of Gympie-Gympie From Your Property
Thankfully, even in New South Wales in Australia, where the plants are more prolific, their growth tends to be restricted to upland rainforest clearings. Although gympie-gympie grows from seed and takes root easily with the right conditions, it would be rare to find this endangered species in a backyard.
If you live in this region and suspect a gympie-gympie has taken root in your garden, it would be wise to call in a horticulturist familiar with the plant. Researchers who have worked with this species wear protective gear—sometimes even Hazmat suits—to prevent being subjected to the sting's severe and long-lasting effects.
Gilding EK, Jami S, Deuis JR, et al. Neurotoxic peptides from the venom of the giant Australian stinging tree. Science Advances. 2020;6(38):eabb8828.