Every holiday season, millions of people bring a tree-killing parasite into their homes that could potentially make them and their pets sick. Most people who hang mistletoe probably think of it as a festive decoration under which couples kiss, but entomologists and botanists warn that it’s far from harmless. Mistletoe is actually a hemiparasite, meaning it attaches to host trees with root-like structures to siphon water and nutrients. Despite its cheerful backstory, entomologist Bill Reynolds calls mistletoe the “thief of trees.” It can’t grow in soil or pots, but survives only by draining its host, sometimes damaging or even killing the tree. The plant grows in round clusters along branches, keeping its leaves green through winter long after the host tree has lost its foliage. Though it may look magical, its parasitic process is remarkably ingenious and potentially dangerous if ingested. If it's left where children or pets can eat it, it can cause stomach pain, nausea, vomiting, and diarrhea. Eating as few as five berries or leaves from a mistletoe plant could be enough to trigger these gastrointestinal symptoms in people. Meanwhile, the ASPCA has listed mistletoe as toxic and recommends contacting a veterinarian if dogs or cats get hold of the parasitic plant.
