Kissing under the mistletoe is an old European Christmas tradition. But those familiar with the springs of white berries hung from the rafters with red ribbon might not recognize it growing wild in the tree tops. The mistletoe plant attaches itself to a tree, drawing nutrients from its host’s branches. But it isn’t just a parasite. In fact, mistletoe is a “keystone” species, which boosts biodiversity by providing food and a nesting place for a whole host of other species. Scientists believe mistletoe it could even play a role in regenerating ailing woodlands.