Mistletoe

24 December 2007

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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For most of us, our awareness of mistletoe is limited to its use at Christmas time for stealing kisses under and for general decorative purposes. Where does this tradition come from? What is mistletoe? Is there something magical about this plant?

Three different families of mistletoe occur throughout the world. Twelve different species (in three genera), all belonging to the Viscaceae family, occur in North America. The most common species in Virginia is Eastern mistletoe, Phoradendron leucarpum, which grows in the Eastern United States as far north as West Virginia. This scientific name, if you are familiar with botanical names, clearly describes an important feature of this plant.

Phoradendron means thief of the tree, and that is exactly what mistletoe is a semi-parasitic plant, parasitizing a variety of trees for water and nutrients while providing for its own food needs through photosynthesis. You may find mistletoe on over 100 species including some of our most common trees: sweet gum, hickory, maple, oak, sycamore, and tulip tree. While mistletoe can damage trees, most often it is not a serious pest in our forests or landscapes. However, heavy infestations can certainly shorten the life of a tree. From a practical standpoint, if you have a mistletoe-infected tree, the only way to kill it is to physically remove it. By pruning off the branch it is on, making the cut 1-2 feet below the parasite, you will hopefully get the whole plant. In most cases, this work should be done by a certified arborist for safety and to make sure proper pruning cuts are used.

The spread of Phoradendron leucarpum is one of the most interesting aspects of this plant. Ripe berries are tasty treats to several common birds including robins, thrushes, bluebirds, and cedar waxwings. After one of these critters eats a number of berries, the seed passes through the digestive tract unscathed and even retaining a sticky covering of hair like threads which work great for sticking to a branch. Seeds may also get stuck on a branch when a bird, who recently dined on mistletoe berries, wipes its beak on a branch or twig.

As unromantic as this may be, this is how a mistletoe plant gets its start. The seed, packed in dung, takes root on thin barked branches. Actually, it does not take root like soil-supported plants, but sends a primary haustorium, or a root-like attachment that penetrates and obtains food from the host to get beneath the bark. Once through the bark, the tree first layer of defense, cortical strands set up just under the bark in a branch like pattern to send out sinkers which tap into the trees plumbing to ensure plenty of water and nutrients for itself.

After about a year of the seed taking root the visible part of the plant will only be a few millimeters long. After it is well established, it can grow several centimeters per year. These aerial shoots could theoretically grow to be hundreds of years old, but are usually only a few years old before being broken off by snow or ice or killed back by freezing. However, this does not kill the plant. It simply sprouts back with a multitude of shoots. It is from these shoots that berries grow which birds then eat unless it is harvested for the holidays.

With their green shiny thick leaves and white or red berries, mistletoe is poplar holiday decor. Of course, it is much more than garland; it is mystery and romance! The history and beliefs about mistletoe go back to the Norse and Druids. The Norse held that if men in battle meet under mistletoe, they had to stop fighting, kiss and make-up. While we do not usually look to meet our enemies under mistletoe today, it seems a reasonable origin.

We can credit the English with starting the kissing tradition as we know it. The proper way to use mistletoe is to wait under it for a suspecting (or unsuspecting) guest and steal a kiss. After the kiss, remove one berry. When the berries are all gone, the kissing is over.

The Druids, on the other hand, believed it held magical and healing powers. Among other properties, it was thought to promote fertility and ward off evil. While today we know the berries are actually quite poisonous if eaten, mistletoe is being explored and in some cases used as an alternative medicine.

Aside from its use in some creams and shampoos, mistletoe is also thought to have some cancer treating potential. According to the University of California, San Diego Medical Center, mistletoe extract stimulates the immune system, induces programmed cell death and offers some protection from potential carcinogens in laboratory and animal studies. Medicinal use of mistletoe is not approved for use in the United States but clinical trials are ongoing.

So as the English say, there you have it. Happy Holidays from Virginia Cooperative Extension!

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.