How Mistletoe Works

Mistletoe is a parasitic plant that grows on trees, particularly hardwood trees like oak and apple. A parasite is a plant or animal that needs another plant or animal to survive. As mistletoe grows on a tree it uses its roots to invade a tree's bark, which allows mistletoe to absorb the tree's nutrients. Sometimes, mistletoe can harm a tree and cause deformities in a tree's branches, but usually it doesn't kill its host. If the host dies, the mistletoe dies. Phoradendron flavescens and Viscum album are the species associated with Christmas.

Mistletoe can produce its own food by photosynthesis (autotropic), and live on its own, but it prefers to grab water and nutrients from its host tree (heterotrophic). It's common for a mistletoe plant to grow on top of another mistletoe plant. If that happens, researchers from the University of California, Riverside found that the mistletoe plants may "share the tree" and rely more on photosynthesis for food to lessen the harm caused to the host tree.

Mistletoe is easy to spot in the winter because its leaves stay green all year long. In the United States, it grows in tropical and subtropical regions (from New Jersey to Florida). Mistletoe has pointy, green, leathery leaves, with waxy berries that are either red or white. The plant's flowers can be a wide variety of colors, from bright red to yellow to green.

Birds eat the berries that grow on mistletoe and eventually leave their droppings at their favorite hangout spot — a tree branch. The droppings contain seeds that sprout roots into the tree branch. The birds also help spread the seed by wiping their beaks on the tree bark to clean off the sticky seeds after they've eaten. The seeds are sticky because of the juice inside the berry. This stickiness helps the seeds stay in the tree rather than falling to the ground. Within six weeks, the mistletoe plant begins growing, although it takes several years to flower.

Lots of myths surround mistletoe. For example, Vikings dating back to the eighth century believed that mistletoe had the power to raise humans from the dead, relating to the resurrection of Balder (also known as Baldur or Baldr), the god of the summer sun.

Balder had a dream that he was going to die. His mother, Frigg, the goddess of marriage and fertility and wife of Odin, was frantic about his dream and said that if he died, everything on Earth would die. To ensure her son's safety, Frigg went to all the elements — air, fire, water and earth, as well as to all of the animals and plants — and asked them not to kill Balder. In much the same way that a child would be teased these days if their mother asked kids not to pick on her child, Balder was teased and had things thrown at him. It was thought that, because of his mother's power, he was immune to harm.

Balder's only enemy, Loki, found a loophole in Frigg's request for her son's safety: mistletoe. As we know, it grows on the tree it attaches itself to, and therefore has no roots of its own and could not be affected by Frigg's request. Loki made a poisoned dart with mistletoe and tricked the blind brother of Balder, Hoder, into shooting the arrow that killed Balder.

For three days, all the elements tried their hardest to bring Balder back to life but failed. Finally, the tears that Frigg cried for her dead son changed the red mistletoe berries to white, raising Balder from the dead. Frigg then reversed mistletoe's bad reputation and kissed everyone who walked underneath it out of gratitude for getting her son back [source: Reshetiloff].

The Miracle Worker

Another myth in mistletoe's past comes from Britain. In the first century, the Druids in Britain believed that mistletoe could perform miracles, from providing fertility to humans and animals to healing diseases and protecting people from witchcraft.

The Druids would cut mistletoe off oak trees in a special ceremony five days after the new moon following the winter solstice. The Druids believed that the mistletoe would become contaminated if it touched the ground, so they used a special white cloth to catch it. The Druids then sacrificed two white bulls while prayers were said, and priests gave out the mistletoe sprigs to the people, who believed they would then be kept safe from evil spirits and storms [source: Reshetiloff]. Modern Druids still regard mistletoe as special.

Mistletoe is also said to be a sexual symbol, because of the consistency and color of the berry juice as well as the belief that it is an aphrodisiac, the "soul" of the oak (or other tree) from which it grows. The origin of the tradition of kissing under the mistletoe is vague. However, the tradition may have stemmed from either the Viking association of the plant with Frigg (the goddess of marriage) or from the ancient belief that mistletoe was related to fertility. Another explanation for the tradition is that it stems from the festival of Saturnalia, a popular mid-December celebration in ancient Rome [source: BBC.com].

The correct mistletoe etiquette is for the person giving the kiss to remove one berry when they plant a kiss. When all the berries are gone, there's no more kissing permitted underneath that plant.

Legend has it that a couple who kisses underneath mistletoe will have good luck, but a couple neglecting to perform the ritual will have bad luck. Specifically, it is believed that a couple kissing under the mistletoe ensure themselves of marriage and a long, happy life, while an unmarried person not kissed under the mistletoe will remain single for another year.

Want some more mistletoe lore? At one point, maidens may have been encouraged to place a sprig of the plant under their pillow at night in the same manner a child places his or her lost tooth in anticipation of a visit from the tooth fairy. Instead of exchanging teeth for money, however, the sprig of mistletoe allowed women to dream of their future beloved. Burning a mistletoe plant was also thought to foretell a woman's marital bliss, or lack thereof. A mistletoe that burned steadily prophesied a healthy marriage, while fickle flames may have doomed a woman to an ill-suited partner.

While mistletoe is widely viewed as a symbol of love and fertility, it also symbolizes peace. Ancient tales tell of enemies who encounter each other underneath trees bearing mistletoe. The enemies lay down their arms, embrace and agree to a truce until the next day [source: Perry]. This act of goodwill is yet another possibility for why we kiss under mistletoe: abstaining from violence and exchanging greetings under the plant may have prompted the custom of kissing.