If you’ve decked your halls with mistletoe this year, you aren’t the only one that finds it a valuable addition to the holiday season. Worldwide, there are over 1500 species of mistletoe. The version we find in our trees is Phoradendron leucarpum. You might see it as a solid ball of greenery in the top of an oak or other tree.
I love the fact that the name mistletoe comes from two old English words, mistel, meaning Dung and tan, meaning Twig, which is a shorthand explanation for how the plant takes hold. Birds like Cedar Waxwings, Robins, and Eastern Bluebirds eat the berries and excrete them as dung in other areas. Though those berries can hold some toxicity, it doesn’t affect these birds who help the mistletoe colonize new trees.
That sticky seed takes hold on the branch, and sends roots deep into the xylem of the plant, allowing it to draw nutrients from the host tree. As the root grows, the plant sends up shoots of double leaves, and eventually the plant will flower and fruit, creating more berries to be spread to nearby trees and branches.
Mistletoe is a hemiparasite, meaning that it does absorb nutrients from the host tree, but it also photosynthesizes on its own. It is unusual for mistletoe to get such a stronghold on its host tree that it kills the tree, but it can weaken the tree, which makes it more susceptible to other parasites and diseases. It also adds to biodiversity in several ways. The most obvious is that it provides habitat for nesting birds and serves as a nectar and host plant for pollinators, but mistletoe has some other advantages: because it has green leaves and flowers in the winter, it provides a source of nectar and nutrition when those resources might be scarce. And most deciduous plants suck all the nutrients out of their own leaves to prepare for fall and dropping their leaves, mistletoe has an almost constant source of nutrition from their host plant. Which means they can drop green leaves, providing more nutrients to the forest floor. In Australia, a study showed that when mistletoe was removed from an ecosystem, 1/3 of the bird species disappeared. Not only those birds who consumed those seeds directly were affected: those who consumed insects from the forest floor that relied on the falling nutrients also suffered.
Closer to home (in the desert Southwest) the western Phainopepla relies on mistletoe for nesting sites and food. In exchange, the Phainopepla is a reliable means of seed dispersal of dwarf mistletoe to mesquite trees.
We’re fans of pruning native (Yaupon, American Holly, Dwarf Palmetto, and Eastern Red Cedar) plants in the backyard for decking the halls, and since I’m not much of a ladder climber, (and I am definitely not someone who is going to harvest it via shotgun!) I don’t often have mistletoe in the house. Wherever you are celebrating, we wish a merry holiday to you and yours!