You might associate holly mainly with a wreath you hang at Christmastime. But there are many species, some of which grow wild. The bright red berries might look inviting but you'll want to stay clear of them as they can cause nausea, diarrhea, vomiting and possibly death.
The leaves, however, are another story. Indians from North and South America have used the leaves of some varieties of holly for medicinal purposes for centuries. The holly species Ilex vomitoria helped induce vomiting, while the Ilex opaca variety was a heart stimulant. Teas from holly leaves have also been involved in combating everything from simple coughs and water retention to joint pain, chest congestion and high blood pressure. They've even been used to cleanse the bowels and increase urine flow [source: WebMD].
Despite such widespread use in certain parts of the world, experts say it's still risky to ingest holly leaves, which can cause diarrhea, nausea and vomiting [source: WebMD].