Mistletoe: Our Favorite Holiday Parasite


Author – Dennis HinkampMistletoe: Our Favorite Holiday Parasite | Live Well Utah

“Don’t get caught under the parasite” sounds like good advice any time of the year. Why is it that during the Christmas holiday we give so much attention to a plant that lives off other plants? And, what is romantic about it?

Mistletoe is a parasitic plant we associate with many Christmas traditions, says Jerry Goodspeed, Utah State University Extension horticulturist. A parasitic plant is one that invades other plants, robbing them of water and nutrients, instead of developing its own root system. Parasitic plants are found throughout the world. A couple invade Northern Utah, although they often go undetected.

“At Christmas time we seem to honor one of the most tenacious parasites around as we buy mistletoe and drape it around our home,” Goodspeed explains. “There is a great deal of folklore and myth surrounding mistletoe. The name comes from the ancient belief that the plant somehow spontaneously sprung to life from bird droppings in the tops of trees. The word “mistel” is Anglo-Saxon for dung, and the word “tan” means twig. Thus, mistletoe could be translated to be “dung on a twig.” And you thought calling it a parasite was bad?

Mistletoe sounds a little better, especially if you have to kiss under it, he adds. Mistletoe was used in ancient wedding ceremonies to confer fertility and life-giving power on the newlyweds. In other parts of the world it was considered a peace plant. Those who were fighting stood under the mistletoe to resolve their conflict.

Oh well, enough of history. Most parasitic plants contain an organ known as a haustorium that functions a little like a root, Goodspeed says. Instead of growing into the soil, it penetrates the bark and obtains its water and nutrients from its host. Of course, this weakens the host plant and, in severe cases, can even kill it. There are two native mistletoes in northern Utah. Both are dwarf varieties, and not the leafy mistletoe we often use in Christmas decorations. Fir dwarf mistletoe (Arceuthobium douglasii) is a parasite to the native Douglas fir, and can attack the sub-alpine firs. Limber pine dwarf mistletoe (Arceuthobium cyanocarpum) is not as common, but occasionally is seen on limber, bristlecone, ponderosa and lodgepole pines.

“Mistletoe does flower, although the blossoms are inconspicuous,” he says. “The flower leads to a small fruit that contains one seed. This fruit is eaten by birds in the trees. Then they deposit the seeds in other tree tops as they sit contemplating the meaning of life.”

Dwarf mistletoe is not common, and since it blends in so well with the host plant’s foliage, it often goes undetected, he adds. It is rarely found in our landscapes and is not considered a major pest in northern Utah.

Enjoy the Christmas holiday with all its traditions. And, just be thankful we kiss under the mistletoe and not a “twig covered with dung,” Goodspeed says.

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