What herb is a popular Christmas decoration, is universally recognized as a symbol of peace, once served as the official flower for the state of Oklahoma, is associated with the cross carried by Jesus, is used to make an anti-cancer medication, and is classified as a parasite—but one that plays a role in biological conservation? Give up? Here’s one more hint: If you were found standing underneath it during the winter holidays, you were (hopefully) rewarded with a kiss.

If you guessed mistletoe after reading our series of clues, then pat yourself on the back! Mistletoe is all of those things and more.

Most of us are familiar with mistletoe in the form of a small bouquet sporting white berries that is hung over doorways to elicit a smooch from those standing under it. However, contrary to popular belief of long ago, mistletoe is not a stand alone plant, shrub, or tree. In fact, it is technically referred to as a hemi-parasitic plant, which means that it latches onto and takes nourishment from the branches of trees and shrubs. The truly remarkable distinction about this herb, though, is the fact that it has reached this potential by making no less than five biological adaptations, while the entire plant kingdom has witnessed only nine other similar occurrences among varying species in the history of evolution. Further, as a member of the Santalales order of flowering plants, mistletoe is capable of manufacturing its own sugar through photosynthesis and producing seeds that are void of testas, or seed coats. Of course, when thirsty for water and other nutrients, it simply taps into the supply provided by its host.

There is an interesting legend surrounding mistletoe that attempts to explain its parasitic status. Early Christians believed that the plant once existed as a small tree and that its wood was used to make the cross upon which Jesus was crucified. From here the story forks into two versions. One maintains that the plant shriveled in shame for its participation in the event. The other claims that God stripped mistletoe of its earthly roots and condemned the plant to forever remain a parasite above ground. Pick whichever account you find most entertaining, but certainty regarding mistletoe’s progression is more likely found in DNA and in bird poop. Through DNA analysis, the international group of botanists, collectively known as the Angiosperm Phylogeny Group, has determined that mistletoe independently evolved into five different families of hemi-parasitic plants representing more than 900 species. By hitching a ride in the feces of birds, the seeds are readily transported to more than 200 species of trees where they self-propagate, often to the point of becoming a pest. However, mistletoe has recently been given a reprieve as a pest and is now considered to be a keystone species with the ability to largely impact the surrounding ecosystem. As such, mistletoe provides sustenance and shelter for many species of birds and animals, as well as contributes to the exchange of pollen between neighboring plants and, therefore, enriches biological diversity.

Mistletoe has long been associated with the furtherance of peace and harmony, as well as renewal from the dark time of the year (winter) to the light (summer). The Druids and Celts believed that mistletoe was a boon to the libido and fertility, as well as personal prosperity. They also attributed protective powers to the plant, even using it as an anecdote to poison. Norse mythology tells us that Frigga, a goddess of love and beauty and wife of Odin, enchanted everything in the natural world from which a bow could be fashioned to harm their sons, Balder and Hod, who were dueling over the feminine affections of Nanna. Unfortunately, mistletoe was overlooked, and the mischievous Loki made a magical spear from it and tricked Hod, who was blind, into using it to launch his brother into death. The tears shed by his grief-stricken mother transformed into the white berries visible on mistletoe today. Of course, as god and goddess, his parents possessed the power to eventually resurrect their fallen son. In a show of gratitude, Frigga declared mistletoe a symbol of unrelenting love and peace, and vowed to kiss anyone passing beneath it. Perhaps this is what inspired future Scandinavians to reputedly lay their weapons aside and embrace their enemies whenever finding themselves standing under mistletoe-laden trees--at least until the next dawn.

In part, the Christmas tradition of kissing under the mistletoe evolved from the story of Frigga. However, it also stems from the customs of Saturnalia, a week long festival first celebrated by the early Romans that promoted all sorts of hedonistic activities, bolstered with the promise that no one could be prosected for any misdeeds. The festival kicked off with the selection of a “Lord of Misrule” by each community on December 17th, who was then forced into an unbridled indulgement of food, drink, and sex. This “lucky winner” would then be sanctimoniously sacrificed on December 25th in the belief that the city’s remaining citizens would be saved from their sins by expelling the evil influences suffered by the poor fellow (or woman). Later, in the hope of enticing pagan participation, Christian leaders incorporated Saturnalia into Christianity, first extending its longevity to 12 days and then tempering its association with lewd behavior by declaring the last day of the festival as the birthday of Jesus. At first, the church accepted that promiscuity would likely continue, and even permitted it. In fact, the first Christmas celebrations were anything but pious. For example, the practice of running through the streets singing while naked persisted, a custom barely recognized today as caroling. The hanging of mistletoe offered an additional license for other salacious public displays, which eventually dwindled to a modest kiss between lovers and friends.

Mistletoe also boasts a long history of medicinal use. In Germany, it is widely used to treat respiratory disorders and high blood pressure. In recent years, mistletoe has received a good deal of attention for its potential value in treating cancer. While the plant contains many active constituents, including amines, terpenoids, and antioxidant bioflavonoids, researchers believe the anti-cancer mechanism may be driven by the presence of sugar-binding lectins. While some mistletoe preparations are made from homeopathic dilutions, the pure extract is marketed under various trade names, most notably Iscadore. In an analysis of existing clinical studies published in the Dec. 18, 2009 issue of the journal BMC Cancer, German researchers from the Center for Integrative Medicine of the University of Witten/Herdecke concluded that cancer patients receiving mistletoe extract as an adjunctive therapy to conventional treatments experience a better survival rate than those who don’t.