Knowing Nature . . .

December 16, 2005
Jocie Ingram

I’ve been gazing up a particular tree lately, noticing a ball of dense growth near the top. I am sure that the unusual growth is a “witch’s broom” caused by mistletoe, but I can’t get closer to take a look. I have been hoping to find a sprig of the mistletoe beneath the tree, blown down by the wind, but no such luck. The inaccessibility of the plant, though frustrating, has prompted my curiosity about it.

Most of us know of mistletoe as a leafy green plant with white berries. Traditionally it was hung in the house at Christmas, and a nearby male kissed any female lingering under it. Today, such a custom seems quaintly old-fashioned and romantic. The origin of the kissing custom dates back to 16th Century England, but the myths and legends surrounding mistletoe go back much further.

The Druids, priests of an ancient Celtic religious order, worshiped mistletoe, believing that it had special mystical powers. This leafy mistletoe grew on the branches of the sacred oak tree. When the oaks dropped their leaves in the fall, the mistletoe remained green and thriving on the tree. The Druids believed that mistletoe, the only living evidence of the tree in winter, held the spirit of the tree after it lost its leaves. They were further impressed by the fact that the mistletoe survived without touching the “vile earth” a fact that heightened its powers. Mistletoe was similarly venerated in Greek myths and Nordic legends.

Despite the historical associations of this plant with healing, endurance and fertility, there is a dark side to mistletoe. Today we know that mistletoe is in fact a parasite. Mistletoe seeds, upon germination, penetrate the bark of a tree through a small root-like structure. Once established, mistletoe puts out ‘sinkers’ into the host tree from which it draws most of its water and nutrient requirements.
Worldwide there are about 2000 species of mistletoe, most of which occur in the tropics. Some are only a few millimetres high, and others are large with showy flowers. Generally there are two types of mistletoe: leafy mistletoe and dwarf mistletoe.

The European mistletoes, featured prominently in ancient myths and legends are leafy mistletoes, the most well known being Viscum album, a species with green leaves and white berries. In North American, most commercially available mistletoe closely resembles the European kind, and is harvested from the southeastern US (Phoradendron spp). The large leafy mistletoes depend upon birds to reproduce. Birds, eating the sticky berries, spread them to other trees through their droppings. This gave rise to the name mistletoe, which literally means “turd on a twig”.

Here in BC, we only have 3 species of native mistletoe, all dwarfs. In our area, only one species of mistletoe occurs, which is the western dwarf mistletoe (Arceuthobium campylopodium). Western dwarf mistletoe may be found on several conifers, but primarily affects western hemlock. Dwarf mistletoes have a stubby appearance and are yellow-green in colour. Leaves are reduced to tiny scales, and flowers are barely noticeable. They aren’t much to look at, and unless you are a forester you aren’t likely to notice them.

Dwarf mistletoes are also considered a serious pest to trees, and can cause stunted growth, and deformities affecting timber quality. In the interior of BC, American dwarf mistletoe (Arceuthobium americanum) infestations on Lodgepole Pine can weaken trees’ resistance to diseases and destructive insects like the pine beetle.

In BC, dwarf mistletoe was never celebrated as having divine properties like the European variety. Despite this, dwarf mistletoes are some of the most exciting plants around. They do not, like leafy mistletoes, disperse seeds through bird droppings. According to Dr Cynthia Ross of the University College of the Cariboo in Kamloops, dwarf mistletoes have a unique water-pump ejection system. Basically, the growing fruit stores water, and when the water pressure builds up, the fruit explodes. The explosion can blast the rice-sized seed up to 65 feet.

Coming back to my tree, I’ve gained some new respect for dwarf mistletoe. Despite its dark side, as a potentially fatal parasite, its amazing explosive seed dispersal impresses me. I can’t help thinking that it is time we started some new myths and legends, celebrating what is in our own back yard. If I ever find a sprig blown down, I’ll hang it up in the house, and perhaps start a new West Coast custom.