If ever there was a plant that embodies humanity’s emotional duality, then it surely must be a mistletoe. Here are species that we variously revile as unwanted parasites, yet see fit to kiss under during the holidays. This love-hate relationship has its roots in both reality and myth, reflecting both plant evolution and human bias. What, then, is the truth about mistletoes? Why should we care about these plants?
Mistletoes belong to the family santalaceae with the prominent genus, Phoradendron, which itself is derived from the Greek words phor (a thief) and dendron (tree). In other words, plants that steal from trees! Since humans have often loved and even worshiped trees and in general despise parasites, it takes simple logic to conclude that we don’t want parasitic mistletoes growing in and harming our trees. Even this assumption, however, does not stand up to basic biological scrutiny.
For example, most mistletoes are not even complete parasites. They are green because of their need to photosynthesize, converting sunlight and carbon dioxide into energy for themselves, and hence are considered hemiparasites – partial parasites. Does this mean that we should, then, half loath them? Indeed not, as further scientific delving will reveal.
A typical mistletoe starts its life as a seed stuck to the branch of a tree, where, if conditions are ideal, it will send root-like structures into the cambium layer or inner bark of the host plant. Even a tiny mistletoe is green, but in general the family has evolved the need to pirate key nutrients and water from its host. Our local species rarely “infest” their host tree to the point of killing it. After all, how can the mistletoes themselves survive if their host perishes?
Now on to well-meaning, if misguided, humans who see fit to knock down mistletoe clumps from trees. Beyond the unlikely demise of the host tree, mistletoe is a key resource for birds in particular. Locally we have several species of native mistletoe, all of which provide key sustenance to a broad spectrum of birds.
Desert or mesquite mistletoe grows almost exclusively in legumes, where it lacks true leaves. Few, if any other epiphytes in local legumes resemble the sadistic-looking green wig that desert mistletoe does, sparking my nickname for it – “Medusa’s hair.”
Broadleaf mistletoe grows in a wide range of trees, including cottonwoods and hackberry, while juniper mistletoe and oak mistletoe make use of their namesake hosts. Studies on Juniper mistletoe indicate that, yes, it stresses its host plants, yet birds that dine on mistletoe fruit also feed upon and help disperse juniper fruit. Yin and yang.
All of these mistletoe species furnish food for phainopeplas and beyond. Northern mockingbirds, bluebirds of all three North American Species, American robins, Townsend’s solitaires, among others, avidly consume the fruit.
Here is where the plant’s life cycle begins, for our local mistletoe fruit is so sticky that it may get temporarily glued to the beak of a foraging bird. In an effort to clean itself, the bird then wipes its bill on a branch, hence planting the seed. Bird defecation is another frequent planting route.
Birds often nest in the cool recesses of mistletoe clumps, further adding to their wildlife value. Spectacular great purple hairstreak butterflies employ mistletoes as their larval food source.
All this to come to the love part of the human-mistletoe equation. Why do some of us kiss under these misunderstood plants during the holidays? Apparently the tradition dates back to a fertility rite performed during the ancient Greek festival of Saturnalia. Romans and their enemies would kiss under mistletoe to reconcile differences and thus garner peace. Ancient Celts viewed white mistletoe fruit as the sperm of Taransis, the god of thunder, hearkening again to fertility.
Think of these ancient rites when you reconcile your own relationship with our much-maligned mistletoes.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS, their Nature Adventure & Conservation organization devoted to protecting the unique biodiversity of the Sky Islands region. Visit: www.ravensnatureschool.org