December 2024 by Ranger Jay Manning

What is Mistletoe? 

When you hear mistletoe, the first thing that probably comes to mind is Christmas time and the tradition of “kissing under the mistletoe”.  Where did this tradition come from, and what is the impact of mistletoe on California? The significance of mistletoe stems from how the plant grows.  

Mistletoe is a hemiparasitic plant that grows berries. "Hemiparasitic" means that mistletoe undergoes photosynthesis but attaches to other plants to steal nutrients and water. Mistletoe attaches to its host through something called a haustorium. A haustorium is a structure similar to a root that grows around or into the host plant to extract nutrients and water.  Despite the seemingly negative nature of mistletoe, this plant has been viewed favorably throughout history, leading to the winter mistletoe traditions still popular today.  

History of The Tradition 

The romantic association around mistletoe can likely be traced back to the 1st century AD and the Celtic Druids. Mistletoe was one of the few plants that could blossom during the cold winters, so the Druids began to view it as a symbol of vivacity. The Druids began to give mistletoe to humans and animals to restore fertility.

Additionally, Norse mythology references mistletoe. When prophecies stated that the god Odin’s son Baldur would die, his mother Frigg, the goddess of love, secured an oath with all the plants and animals that they wouldn’t hurt Baldur. However, Frigg didn’t consult with mistletoe, so Loki made an arrow from mistletoe to kill Baldur, who was otherwise invincible. According to another version of the myth, the gods resurrected Baldur from the dead. After this, Frigg stated that mistletoe was a symbol of love and promised to give a kiss to all those who passed beneath it.  

Throughout history, mistletoe has been collected around the summer and winter solstice. Leaders traditionally decorate their homes with mistletoe around Christmas time, unrelated to the present-day Christian holiday. The Romans also used mistletoe to celebrate Saturnalia, a pagan celebration of Saturn, which took place around Christmas time.  

What's up with the kissing part?

The strong association with kissing under the mistletoe is thought to have come from Ancient Greece. Due to mistletoe’s association with fertility, it was used during marriage ceremonies. Later, in Victorian England, men were allowed to steal a kiss from any woman under the mistletoe. If the woman refused, this was viewed as bad luck. Due to mistletoe’s romantic and seasonal association, mistletoe is still strongly connected to Christmastime/winter traditions. In addition to mistletoe’s association with traditions, it also impacts the natural environment.  

Mistletoe in California 

There are over 1000 species of mistletoe around the world. The two main types of mistletoe in California are dwarf and true mistletoe.

Dwarf Mistletoe

Dwarf mistletoes are small, leafless parasitic plants. These plants are relatively host-specific, meaning individual dwarf mistletoe species usually infect one species of trees. In California, there are three species of dwarf mistletoe. All three species attack conifers (fir, pine, and hemlock trees). Dwarf mistletoe can slow tree growth, lower seed production, and can impact branching structures. If a tree is infested by dwarf mistletoe in the long term, it may kill the tree. Although dwarf mistletoe can kill a tree, it takes a while for this to happen; therefore, management is possible by trimming infected branches and removing infected trees. The dwarf mistletoe seeds spread by shooting up to 50 feet out of ripe berries! 

True Mistletoe

Another type of mistletoe is true mistletoe. True mistletoes are also known as “leafy mistletoes” to distinguish them from dwarf mistletoes. True mistletoes are not species-specific like dwarf mistletoes. They will infest mostly hardwood trees such as oaks but will sometimes infest conifers. True mistletoes are not as damaging to a tree as dwarf mistletoes. This is because dwarf mistletoes, although capable of photosynthesis, get almost all their fixed carbon from their hosts, whereas true mistletoes photosynthesize more and, therefore, are much less reliant on their hosts for carbon.  

Although true mistletoes are less damaging to their hosts, they can still negatively impact a host tree. One issue that may occur due to true mistletoe is drought stress. When there is limited water, true mistletoe can steal necessary water from the tree, causing it to begin dying.  Additionally, larger and heavier mistletoes can damage tree branches on the host tree. The seeds of true mistletoe are usually spread with the help of birds. Berries produced by true mistletoe are sticky and can be passed from tree to tree on the bodies of birds or when birds eat the berries and excrete the seeds.  

Benefits of Mistletoe 

Despite the generally negative view of mistletoe and its relationship with its host trees, research shows mistletoe has positive impacts. Mistletoe is a food source for many species, and some birds and insects rely on it to survive. Mistletoe can also serve as a nesting site or cover for animals. In some areas, mistletoe has been important in reducing the decrease in bird populations. Additionally, areas with abundant mistletoe have been linked to increased bird diversity.  

Birds and insects aren’t the only ones who benefit from mistletoe; mammals such as squirrels, deer, and cattle will eat mistletoe, especially in the wintertime when there is less foliage.

In fact, I have often seen deer in the park eating mistletoe from oak trees. Next time you’re in the park, look in the surrounding oak trees for mistletoe with a little more knowledge about this hemiparasitic plant that plays a not so black and white role in our ecosystem.