Kissing under mistletoe is a weird tradition. There are several types, European mistletoe (Viscum album) is the type that is most known for kissing. This is the traditional plant of literature and Christmas celebrations. Kissing under the mistletoe is referenced from as far back as 16^thcentury England to Christian literature 300 years AD. The Celts wrote about some of the earliest uses and importance of the plant. It was also written about in Greek myths, and it was sometimes referred to as the “Golden Bough." Norse mythology also includes references to it. In the Middle Ages, people believed it possessed mystical powers that could ward off evil spirits and the devil, as well as bringing good luck.

European Mistletoe grows mostly on apple, poplar, willow, lindens, and hawthorn trees. The variety that grows on oaks is Eastern mistletoe (Pharadendron serotinum), and it is prevalent in North America.

Interestingly, in Fairfax County, mistletoe seems harder to find the closer we get to the Potomac River. The bunch shown in this picture was in Herndon, VA. The other pictures were from Vienna, VA. Drive along the Fairfax County Parkway or Route 28, and just look along the sides of the road. It's easy to find!

Interestingly enough, this mythical plant is actually a type of parasite, specifically a hemiparasite. It can make some of it’s own food, because it has chlorophyll, so it is not fully depended on the host tree. The root system penetrates the bark of the host to find a source of water and nutrients. Seeds are either passively dispersed or dispersed through birds. The seeds are able to pass through a birds digestive track uninjured. They have a special gluey substance, called viscin cells, that help them stick to tree bark so that they can germinate.

It takes a lot of mistletoe to kill a tree. Most commonly the branches past mistletoe infections are stunted, and the tree isn't harmed otherwise.

Take away: Mistletoe is a parasitic plant with a long history.

References:

Britannica

Why Christmas?

Tainter, F.H. 2002. What Does Mistletoe Have To Do With Christmas? APSnet Features. Online. doi: 10.1094/APSnetFeature-2002-1202