Mistletoe is the poisonous plant that is connected to kissing and Christmas.
Climbing on trees, mistletoe is a semi-parasitic plant. It bears tiny white berries that, if consumed, are toxic. A number of symptoms, such as nausea, vomiting, diarrhea, and cramping in the abdomen, can be brought on by the berries. Mistletoe poisoning can cause seizures and even death in extreme situations.
Mistletoe is a common Christmas decoration, despite its deadly berries. It is frequently hung over fireplaces and in doorways. It is believed that the custom of sharing a kiss beneath the mistletoe during the holiday season came from the ancient Norse and Celtic cultures.