June 16, 2025, 9:45 am | Read time: 2 minutes
A copper nail is said to be enough to kill an entire tree—a myth that has persisted stubbornly for decades. But is there any truth to it, or is it just an old rumor? myHOMEBOOK investigates the matter.
A tree right on the property line can quickly become a nuisance–it blocks light, sheds leaves, and causes disputes with neighbors. When cutting it down isn’t an option, some resort to questionable ideas. According to a widespread legend, a simple copper nail is enough to discreetly poison a tree. But is that really true?
What’s the Truth Behind the Myth?
Using a copper nail to kill an entire tree is a persistent myth, even though it was debunked decades ago. It’s a stubborn misconception.
The myth likely originated from the knowledge that copper can be toxic to plants, humans, and animals in high concentrations. For example, copper bands are used to keep slugs out of gardens, and copper coins are used to combat bacteria in flower water. However, healthy trees have a special ability: they can isolate local injuries, preventing the poison from spreading throughout the plant.
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Scientists Addressed This in 1976
The myth of the copper nail has persisted for decades, which is why it was debunked in an experiment at the University of Hohenheim in 1976. At that time, five to eight copper nails were driven into spruces, birches, elms, ashes, and ornamental cherries. Control experiments were also conducted with nails made of lead, iron, and brass.
In all cases, the trees remained unharmed and survived the experiments. The trees isolated the wounds in the wood, and later examinations only found slight discolorations at the point of entry.
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Iron Nails Are the Greater Evil
While the myth of the copper nail in the tree persists, the iron nail often goes unnoticed. However, it should not be driven into the tree–for example, to attach a birdhouse or hang a garland.
Iron nails are extremely prone to rust. Even if they are in a spot that rarely gets rain, iron nails will eventually start to rust. The rust then embeds itself in the tree and can spread to the wood, increasing the risk of infection with bacteria, viruses, and fungi.