Do people kiss beneath the mistletoe to keep their minds off the plant itself? If you were to get to know the white-berried shrub, love and joy might not be the upwelling emotions.

Many folks know that the berries and leaves are toxic, but less known is that the shrub grows high in the branches of trees. Where does it put its roots? Under the skin of its host, supping from the tree's veins.

One or two mistletoe bushes in an otherwise healthy tree will deplete it, though not to the point of death. Look hard in the canopy of maples and oaks: That squirrel's nest, if green, may be a mature mistletoe working its macabre magic.

This sinister trait has resonated in cultures through the ages. In Greek mythology, Persephone unlocked the gates to the underworld with a wand of mistletoe. The ancient druids venerated mistletoe for its powers, believing that when the plant was growing on oak trees, as opposed to apple, it was particularly sacred.

The tradition of kissing beneath it, based loosely on Celtic lore, became popular in the 19th century along with other yuletide rituals.

Colonists left behind the European mistletoe, but in Jamestown, at least, found an abundant American version. Although hardy to New Jersey, the American mistletoe is common only in the South and especially in lowland areas, where its favored hosts grow - it can appear with such abundance as to kill trees, said Lytton J. Musselman, a botanist at Old Dominion University in Norfolk.

Most clumps of mistletoe are found 20, 30, 40 feet aloft, grown from seeds either passed through the guts of birds or rubbed into the bark by their beaks as they seek to clean off the sticky berry.

Many of the sprigs sold for the holidays hail from the Carolinas or central California. The San Joaquin and Sacramento Valleys are particularly afflicted, said Ed Perry, a University of California extension agent in Modesto. The species is drawn to streamside plantings of cottonwoods, ash, locusts and silver maples and has spread to city neighborhoods, he said.

In the mid-Atlantic region, the plant is less common and rarely abundant enough to imperil its hosts. It is, I think, a treat to find mistletoe.

Roderick Simmons, a plant ecologist with the City of Alexandria, Va., told me of an exciting discovery of a mature mistletoe in the middle of Old Town, not only in a well-traveled block of Victorian rowhouses but growing just four feet off the ground. I set out to find it, and there it was in the middle of a snow squall, sprouting robustly from a 20-year-old honey locust.

This specimen was special for two reasons. Simmons said this was the first record of mistletoe's growing in Alexandria since the 1880s. And because it was so low, one could study it without climbing into a cherry picker.

If one could find a seed source (the sprigs sold for the holidays often contain berries made of plastic), one could try to propagate mistletoe on a suitable host tree, though this is a hit-or-miss affair. My desire to start a pet mistletoe goes beyond the idea of having a mythical and beautiful native plant illuminating the winter landscape - it might also contribute to the spread of a lovely butterfly.

The larvae of the great purple hairstreak feed exclusively on mistletoe. The adult, about the size of a quarter, sups nectar in the summer from the native shrubs buttonbush and summersweet, and its upper wing surfaces are a glittering iridescent blue.