There were the fairy rings to be wary of, for if a human were to fall inside one, he could be taken captive by the fairies. Foxglove was considered sacred, and anyone who messed with it could call down upon himself the wrath of the little people. But around the time of the Victorians, a new interest arose, giving fairies a somewhat less ominous reputation. They were seen primarily as tiny little Tinkerbell types, with wings and magical powers. When I think of fairies, this is how I prefer to think of them, rather than as baby snatching imps.
Fairies have been know to be mischievous.
They like to play tricks, and can lay a curse if messed with. Well, it's happened to some, and a good Irishman would immediately know why and what to do. There are those who say it's a spot where a corpse has lain on the way to its final resting place. But in reality, it is a fairy curse. Those who live near patches of such grass have been known to keep extra food on hand in the case of afflicted travelers knocking on their door.