Pucker Up: Mistletoe Ecology

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Mistletoe creates nest-like structures in trees. Image by HFK.

Mistletoe is known as the plant of Christmas romance. When Mommy kissed Santa Claus, it was probably under a doorway hung with mistletoe. What is this lip-puckering plant, anyway?

Mistletoe is the master of relationships. It’s a hemi-parasitic plant, which means that it uses food from its host to survive.  All mistletoe species can make some of their own food, but dwarf mistletoes rely on their host plant for the majority of their needs, particularly carbon, while leafy or true mistletoes collect water and nutrients from their hosts and create other food through photosynthesis.  The leafy version has larger leaves and smaller berries, and it’s this one that you’d usually kiss under.

Mistletoe the Monogamous

Mistletoes grow on all sorts of trees, from oak to mesquite, from cypress to fir. Different species of mistletoe tend to be specific to certain host plants. For instance, the White Fir True Mistletoe (Phoradendron pauciflorum Torr.) tends to grow on – you guessed it – white firs.

Mistletoe: Fueled By Hormones

When dwarf mistletoes attach to the tissues of trees, they cause the tree to create interesting structures that are often called witches’ brooms. These structures look a lot like the tree has grown a broom or a nest in its branches. In fact, these bunches of shoots are caused by the mistletoe’s hormones. These hormones encourage the tree to invest a lot of energy in developing tissues that support the mistletoe.

A Rebound Relationship

Mistletoe is also proficient at finding new hosts. When it is mature, the mistletoe sends out a seed, propelling it into the air and onto nearby trees. The seed is sticky and attaches to plants that are close by, starting yet another mistletoe on the new plant.

Birds are also good at spreading mistletoe. They eat the berries and then move to another tree, where they spread the parasitic plant through their feces. Romantic? Possibly not, but it’s certainly a successful strategy.

Getting Burned

Mistletoe can become a prominent feature in forests, moving from tree to tree and infecting many of them. Fire is one way to control the population of mistletoe. When the mistletoe-impacted trees burn, the mistletoe itself generally dies. New trees sprout up more quickly than the mistletoe arrives, and for a time, there is little mistletoe.

Mistletoe and Christmas Time

Like many common names, the name mistletoe is attached to a number of different plants, most in the Order Santalales. Is it a coincidence that this plant that’s so closely related to Christmas has Santa in its name? In fact, mistletoe is related to many other winter and Christmas traditions. The Druids considered it to be a sacred and powerful plant.

Why do we kiss under this prolific parasite? Some say that it’s because it’s a tree-dwelling plant, so it grows closer to the heavens and has special powers for good. Its white berries promise peace and happiness. In Norse folklore, Mistletoe was used to kill the son of the goddess Frigg. Frigg was so sad that her tears became the berries and she made the plant pledge that it would bring joy instead of sadness to others.

From its ecology as parasite to its role as a bringer of peace and joy, mistletoe has an intriguing connection to the plants and people around it.

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