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Photos by Larry Sagers
Mistletoe has red or white berries that have sticky seeds.

Are you ready to pucker up and kiss under the mistletoe this season?

Are you getting romantic vibes from thinking about the kissing plant?

Have you ever wondered why this, of all plants, should have this loving and fraternizing reputation?

I can't hope to explain the associations this plant has with Christmas and love. Because of my training, I have very different associations between this plant and the trees it lives in.

To plant pathologists and others who work with plant diseases, mistletoe is a serious plant parasite that weakens and kills trees.

To make the problem even worse, it is not easy to control. It spreads prolifically, and once it establishes in a tree, it defies eradication without very costly, time-consuming methods.

The other serious problem is that this parasite, unlike most other plant disease-causing organisms, produces seeds. The seeds form in red or white berries that are usually very sticky. Birds spread the seeds because the seeds stick to their beaks, and after they fly to other areas, they wipe their beaks on a tree's bark to clean them off.

The sticky seeds then remain stuck to the tree.

Birds also deposit the seeds with their droppings.

The seeds sprout, and within six weeks, the mistletoe invades the tree. The parasite grows slowly, and it can take up to five years for a new plant to start flowering.

During the Middle Ages, people believed in spontaneous generation, so they thought mistletoe grew from birds.

The name possibly originates from the word "misteltan" — "mistel" meaning "dung" and "tan" meaning "twig."

Most mistletoe species are hemiparasitical, or partially parasitic, because even though they have green leaves that photosynthesize, they invade the tree with a root structure that eventually allows them to extract water and nutrients from the tree.

Since most true mistletoes do not grow in Utah, it is hard to imagine the devastation this plant causes.

Because the parasite has green leaves, it is often not noticed while the host trees are covered in leaves.

While I was in England early this spring, I saw deciduous oak trees that looked like they had numerous green leaves in March. Unfortunately, the green came from the leaves on the life-sucking mistletoe, not from the oak foliage.

The custom of kissing under the mistletoe is thought to come from Celtic and Norse mythology. Early Christians condemned using mistletoe as evil and pagan. However the custom of kissing under the mistletoe became a Christmas ritual of a holy kiss of peace and pardon from priests to their congregations.

Mistletoe was long associated with the winter solstice, because that is when it bears fruit. One Christian myth claimed that mistletoe was once a tree that had provided the wood for the cross, but after Christ was crucified, it was forever cursed to be a shriveled, parasitic vine.

By the 18th century, the custom evolved into stealing a kiss from anyone found standing under the mistletoe. It caught on in England but had a harder time in Puritan America.

Reportedly, author Nathaniel Hawthorne was shocked by the continual and licentious use of these kissing balls while traveling in England in 1855.

He reported the "one berry and one kiss rule." A man could kiss a woman under the mistletoe if he picked a berry each time he puckered up. Once all of the berries were gone, the kissing stopped. Needless to say, most of those who indulge these days no longer play by these rules.

In our native Utah forests, dwarf mistletoes attack spruces, firs, junipers and some other trees. While this type of mistletoe is not as showy, it, too, is a very serious and persistent problem that destroys the tree form and growth.

Infested trees appear to have yellow, very dense, distorted foliage. The parasitic plant sections have yellowish-green, reddish-brown or olive-green shoots. The plant often grows short, distorted branches referred to as witches' brooms.

If trees near a home or cabin show problems, prune away the distorted shoot growth. There are also sprays that can reduce shoot growth and seed formation.

Hopefully, you can still feel some of the Christmas spirit and a little Christmas romance after learning about this plant.

While the legends, mythology and the growth habits and pathology are interesting, any celebration that promotes peace on earth is welcome.

Larry A. Sagers is a horticulture specialist for the Utah State University Extension Service at Thanksgiving Point.