There is a whimsical old Christmas holiday tradition of hanging a bough of Mistletoe (genus Phoradendron) in a doorway and using it as a lure or an excuse to peck the lips of a significant other who happens to occupy the same space. The idea is as old as the Druids and was a public mania when I was a kid. Small twigs of the stuff were packaged in cellophane and available at cash registers for spontaneous purchase. Later, my friends and I got so rabid about it we conducted mistletoe hunts from a boat, using a long-barreled goose gun to collect huge quantities. Alas, the custom is not as prevalent as it once was but kissing, thank goodness, has never gone out of style.
After the leaves drop from the trees in winter it becomes evident to what extent these evergreen, parasitic shrubs infest the woods. Their dark, clumpy forms are easy to spot high up in the bare trees. To be more precise, they are “hemi-parasitic,” that is, they can get some of their nutrients on their own with the use of chlorophyll in their leaves but they usually get most of it, plus a fair measure of water, by mercilessly sucking it out of the host tree. They actually take root in the fiber of the tree’s high branches with an organ called a haustorium. These can be so detrimental to the host it may eventually result in the branch falling off, taking the parasite with it.
You have to wonder how people got the idea of mixing a botanical parasite with love.
Curiously, the etymology of the word mistletoe derives from old German for dung (mist) and branch (tan). It turns out, the sticky white seeds of the plant, which are toxic to humans, get stuck to the beaks of the birds that gobble them up. Since they have no table manners or napkins, these birds are known to wipe the seeds from their beaks (or poop them out) on tree branches, thereby spreading the plant to another host. Those Germans sure had keen powers of observation. So do modern naturalists. They have determined this parasite is actually important to the ecological diversity of the forest by providing food, pollen and nesting material to the different animals that may actually depend on them.