Natural History of Holiday Plants Exhibit
Evergreens | Holiday Color | Poinsettia | Holly | Mistletoe
Christmas Cactus | Christmas Tree | Common Holiday Plants
Scientific name(s): Viscum album (Old World), various Phoradendron spp. (New World), especially Phoradendron macrophyllum in San Diego County
Plant family: Viscaceae (Mistletoe family)
Mistletoes are perennial, flowering plants that are parasitic on aboveground parts of woody trees and shrubs. Mistletoes have specialized roots with the ability to penetrate a host plant and absorb nutrients. Most mistletoe species are either full parasites like dwarf mistletoes (Arceuthobium spp.) or partial parasites, called hemiparasites, like the mistletoes (Viscum and Phoradendron spp.) used for holiday decoration. Hemiparasites get a portion of their nourishment from their host, but they also contain chlorophyll, making them green and giving them the ability to conduct photosynthesis and make some sugars for themselves. The berries of most mistletoe species are white, but they can also be yellowish or even pink to red. Most parts of a mistletoe plant are toxic and should not be eaten.
In Europe, the species of mistletoe most frequently used is in the genus Viscum (Viscum album), but in the New World various species in a different genus in the same family, Phoradendron, are used. In San Diego County, we have six different species of mistletoe (Phoradendron spp.) and two species of dwarf mistletoe (Arceuthobium spp.). The most commonly used species during the holidays in our region is the Big Leaf Mistletoe (Phoradendron macrophyllum), which is parasitic on various riparian trees and shrubs including sycamores, cottonwoods, willows, and alders.
How do mistletoe seedlings get up in tall trees or spread from one host plant to another?
Some mistletoe species have explosive berries that can propel their sticky seeds outward for some distance, giving them the opportunity to come in contact with branches or treetops away from the mother plant. However, most often the mistletoe berries are eaten by birds that fly from tree to tree and the ingested seeds pass through the digestive tract and are expelled in fecal matter. Frequently, this bird excrement lands on the branches of trees where birds perch. The mistletoe seeds can then germinate in a new place and penetrate the host plant. It is believed that the common name "mistletoe" was derived from this method of seed dispersal. The origin of the word "mistletoe" appears to come from the Anglo-Saxon (Old English) words "mistel" which means dung and "tan" for twig. Thus, mistletoe literally means "dung-on-a-twig."
Why are mistletoes used during the holidays?
Throughout history and in many different cultures, mistletoes have been a source for many concepts, symbols, and rituals. Probably due to their parasitic nature, elusive method of dispersal, and strange growth habit, many cultures have revered, feared, or thought them to have magical properties. As a result, mistletoes have been interpreted in varying ways such as: symbols of fertility and romance; aphrodisiacs; bestowers of life; protectants against poisons, witches, or evil spirits; and even plants of peace under which opposing groups can make truces. The act of kissing under a sprig of mistletoe may date way back to the Greek festival of Saturnalia where it was believed to confer fertility. But, no matter what symbolism you may interpret with mistletoes, they all exhibit a fascinating life history and are an interesting part of our natural, botanical world.
Is there any mistletoe etiquette?
Correct etiquette says that a person should pluck a berry from the mistletoe branch each time they kiss under it, and when there are no more berries left on the plant, there should be no more kissing. (Please note, if you are going to follow this suggestion, you should buy a larger bag of mistletoe this year from our Museum's Canyoneers at Christmas on the Prado!)
Continue to Christmas Cactus
Text by Jon P. Rebman, Ph.D., Curator of Botany;
Arceuthobium camplyopodum (dwarf mistletoe), photo courtesy of Norm Roberts