The bay's ordinary life is culinary and it involves a real botanical trap.
Laurus nobilis is the bay of the kitchen, of Mediterranean origin, a slow-growing evergreen that will make a substantial tree but is usually kept clipped. Its leaves are used dried in stocks, stews and marinades and are removed before serving, chiefly because they stay stiff and sharp-edged rather than because they are harmful.
Several unrelated plants are also called laurel, and some are dangerous. Cherry laurel, Prunus laurocerasus, is a common hedging shrub whose leaves smell of almonds when crushed because they release hydrogen cyanide on damage; it is not a culinary herb, and it has caused poisonings. Mountain laurel, Kalmia latifolia, is a North American ericaceous shrub containing grayanotoxins and is likewise toxic. California bay, Umbellularia californica, is edible but much stronger than true bay and can cause headache. The shared common name reflects leaf shape and evergreen habit and nothing else; the plants are in three different families.
The magical uses recorded for bay (a leaf under the pillow for true dreams, a wish written on a leaf and burned, a tree by the house against lightning), are English folk practice of uncertain age, transmitted through the herbal and almanac literature. The protection against lightning is the oldest strand and is classical: Pliny reports the belief, and it is attached to the story that the emperor Tiberius wore a laurel wreath in thunderstorms.