Naturespeak 

Mistletoe

By Veronica Sommerville

At this time of year, a mention of mistletoe evokes blushing thoughts of stolen kisses, dressed in your Christmas best, joyously celebrating the holiday season. Beyond Christmas, mistletoe has been revered through centuries as a powerful plant with numerous uses and benefits. It has had many reputations through the ages as a symbol of fertility, luck, peace, an aphrodisiac, and a protector from evil spirits.

Mistletoe is a parasitic leafless, flowering plant that exists by infecting live trees, where it will exploit them for food, water and general life support. There are many different types of mistletoe and they are usually host tree specific. In this area we have the Western Hemlock Dwarf Mistletoe, Arceuthobium tsugense , where as in the Interior Lodgepole Pine Dwarf Mistletoe, Arceuthobium americanum , is prominent. The preferred host of our mistletoe is the Western Hemlock but this species will infect some fir and pine species as well. Mistletoe is not picky about age, however, severe visible infections occur mainly in trees larger than 10 metres.

The female mistletoe plant produces berries from which sticky seeds can be launched into the surrounding landscape up to an impressive distance of 15 metres. Once the gluey seed lands amongst the unsuspecting canopy, it must infiltrate the bark of the innocent host. Once this is accomplished, and the season is right, germination begins. Successful troops deploy root-like strands that penetrate into the nutrient-rich inner workings of the branches. Sinkers embed themselves in the outer woody layers which can cause the bark to swell and will account for later disfigurement termed "witches broom." The infected region draws nutrients from the healthier areas causing increased growth in the battle zone while the other areas begin to die off. This causes a large, woody, broom-like whorled growth. A clearly evident witches broom is the result of many years of infestation as the life cycle is a slow one. One broom on a mature tree can be 100 years old. A female plant will produce seeds ready for dispersal after an absolute minimum of four years, so infection spread can be slow.

Mistletoe infection can seriously affect the productivity of a stand. The wood becomes weaker, stunted, misshapen and is unable to achieve large diameters. The mistletoe wound provides an increased opportunity for insects, fungus and disease to attack, further damaging a stand. With increased rot and decay, weakened branches with large witches brooms become a hazard in recreational areas due to breakage.

Mistletoe cannot live without the graciousness of its host. If the branch it has infested dies, it too will die. As it cannot live in snags or downed wood, it is possible to remove invasions completely with fire or clear cutting. This may not be the most desirable course of action. A witches broom provides great nesting habitat for many bird species. The spread of mistletoe from stand to stand can be slowed or stopped by barriers such as rivers, roads or vegetation bands that are not susceptible to infection.

Wherever the traditions and beliefs came from about the powers of this strange, powerful plant, it certainly has an interesting history. Whether it makes me feel like puckering up is another thing. Happy Holidays!

For more information on the Whistler Naturalists, please contact Veronica Sommerville at whistlernaturalist@canada.com .

Christmas Bird Counts

Thank-you to everyone that participated in Squamish and Pemberton!

Whistler: Dec. 21; contact Michael Thompson (604-932-5010).

Lillooet: Dec. 29; contact Ken Wright (250-256-4702).

Sightings

To report noteworthy bird sightings any time of year, please contact Michael Thompson (932-5010; email: redpath@telus.net).

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