Funny things these, never really heard about or seen these before. Now nearly every time we go to a bit of wood where there is a fallen tree, we find one.
One form of votive offering is the token offering of a coin. The remains of one such tree can be found near Ardmaddy House in Argyll, Scotland, a hawthorn, which is a species traditionally linked with fertility. The trunk and branches are covered with hundreds of coins which have been driven through the bark and into the wood. The local tradition is that a wish will be granted for each of the coins so treated. https://en.wikipedia.org/wiki/Wish_tree#Coin_trees