The chance discovery of a carved symbol on a waterlogged tree of the six–ninth century AD may be the earliest mark on a living tree that has so far come to light. Given its rarity, an obvious interpretation remains elusive, but the authors review a wide range of possibilities from analogies ancient and modern. Symbols on trees have been used to mark trails, the ownership of land and resources, and all manner of votive moments from superstitious sign-making, worship of a god, thanks for a successful hunt or the memory of a loving tryst.