Library of Congress Some plants are so entwined with tradition that it’s impossible to think of one without the other. Mistletoe is such a plant. But set aside the kissing custom and you’ll ...

And why are people so amorous when they find themselves beneath it? Mistletoe, a parasitic plant, is actually accustomed to the suspension: In nature, it grows only on other trees’ branches.

Mistletoe is a hemiparasite, meaning it carries out photosynthesis of its own while latching onto the roots and shoots of another plant. There are nearly 100 varieties of mistletoe across ...