Everyone knows the holiday tradition of hanging mistletoe in the doorway with hopes of stealing a kiss from anyone who should happen to linger beneath it. Botanists know white mistletoe (Viscum album) as a parasitic plant that derives most of its nutrients from the host tree, and it is listed as a noxious weed in California. How did a weedy parasite come to symbolize Christmas cheer?

Mistletoe is native to Europe, where pre-Christian inhabitants revered the oak. Anything found in an oak was believed to be a gift from heaven, and since mistletoe strongly prefers soft-barked trees in the apple family, it was a rare sight on an oak. The golden yellow leaves of mistletoe remain after the oak leaves fall, and it stands out strongly against the pale winter sky. People believed that it absorbed the oak’s power for the winter, which would remain as long as it was kept suspended off the earth. Mistletoe was hung at the doorway to keep the household safe from magic, fire, and evil spirits. As Christian thought replaced older beliefs, medieval Europeans maintained their reverence for mistletoe by creating a new mythical history. One story was that mistletoe, formerly a majestic tree, became a shrubby parasite after its wood was used to make the Cross. Mistletoe came to symbolize peace, and exchanging a kiss beneath the mistletoe was a popular custom in England by the 1500’s.

Mistletoe berries are poisonous to people, but relished by birds. Mistletoe is spread from tree to tree through seeds in bird droppings. The mistle thrush of Europe, a cousin of our American robin, may have been named for its love of mistletoe berries.