As with almost anything on this Earth, trees have been the subject of many urban legends. One of the most persistent legends involves someone killing off their stubborn neighbor’s overbearing tree without the said neighbor realizing that something was up. Legend has it that a single copper nail driven into the base of the tree killed it. The nail supposedly poisoned the tree as the metal oxidized and due to its size, remained largely undetected.
Thus, a lot of people who need to get rid of an obtrusive tree in an unobtrusive way often ask if it is really possible to kill it using a copper nail. Some gardening veterans swear by it, while the more skeptical ones point out the fungicide properties that are inherent in the copper metal, which would make it actually helpful to the tree.
The truth is that it all depends on how the copper nail method is applied. It’s true that copper does have fungicidal properties that can actually speed up the healing of tree tissue around a copper piece or nail, thus rendering the tree generally unharmed. However, while a single copper nail is hardly enough to poison a thick, fully-grown and flourishing tree, hammering in an entire box of copper nails into the base of one is a different story altogether.
Copper nails have a two-pronged approach to killing off a tree. Firstly, they can destroy the growth cells underneath the tree trunks, but this would only be true if you were to use big, long copper nails rather than short, tiny ones. The latter would not penetrate deep enough into the tree and its relatively puny copper content would not make much of an impact on the health of the tree.
The former, on the other hand, would not only accomplish the things that short, tiny copper nails could not, but they could also puncture and thus eradicate the tree’s growth cells much more. Without its growth cells, the tree’s regeneration capabilities are hindered, making it more vulnerable to disease.
The second phase of the copper nail attack would explain why you can’t just use nails that are made of any other metal. In its solid metallic phase, copper is not really harmful for trees. However, it tends to oxidize when a high concentration of it is embedded into a wooden trunk. This oxidized form is highly poisonous to the tree. Thus, if you hammer a massive amount of big, long copper nails around the base of a big tree, then it won’t be too long before it starts to weaken from the poison.
Conclusively, a tree that has been subjected to the copper nail method dies as a result of having a diminished healing capacity and being exposed to a highly poisonous substance from the inside over a prolonged period of time.
It should be noted, however, that the health of a tree always factors into the effectiveness of the copper nail method. Robust, healthy trees that are rooted in fertile ground, for instance, are less vulnerable to the copper nail method than trees that are not such.