"The Happening" and Plant Science

"All the things in nature, and all the things that I learned about neurotoxins, and plants, and how they behave, and how they communicate with each other, it's fascinating. It's one organism."

And while Shyamalan's ecological nightmare is fiction, it's no secret to scientists that plants do wage chemical warfare. The defenses that plants have evolved to protect themselves from danger can sometimes pose real danger for animals and people.

Lewis Nelson is a medical toxicologist working at the New York University Medical Center, and is co-author of the "Handbook Of Poisonous And Injurious Plants." He says that while the film's premise is clearly fiction, it does have some basis in fact.

"The idea that plants have neurotoxins is not farfetched at all. The idea that plants can cause people to get neurologically toxic is not farfetched at all."

He recalls a case in the South Pacific where the toxic cycad plant was being eaten by bats known as flying foxes. "The cycad toxin was building up in the flying foxes. The people were eating the flying foxes and getting this terrible neurotoxic syndrome."

Nelson says the people ended up with a degenerative illness resembling Lou Gehrig's disease. However, extreme cases like that are rare, and most of us know to watch out for wild species like poison ivy and poison oak.

But, just when you thought it was safe to go back in the garden, horticulturist Jody Payne, who works at the New York Botanical Gardens, notes that many backyard plants can also be toxic.

"Any part of this plant is poisonous," she says, pointing to a pink-flowered foxglove plant, "so you want to stay away from it. You don't want to ingest it."

Simply touching the common nettle can cause blistering and swelling. Ingesting a foxglove can be deadly. And Payne says you should never burn poisonous plants because inhaling the smoke can be extremely toxic. But, as she makes clear, the best way to avoid harmful exposure is to simply be aware of the dangers in the first place.

"Learning about your plants is important, and making sure that your children are aware that they shouldn't put anything in their mouth that grows," she says, adding, "the more you know about your plants, the better off you are."

And toxins in plants aren't always a bad thing. Nelson and Payne both point out that they are often put to good use in the development of new medications. Nelson says, "Many plants contain drugs that we currently utilize. Many plants contain drugs that we don't even know about."

He emphasizes that it's the dosage that's key. A small amount of an herb can be medicinal, while a larger dose of that same herb could be toxic.

That element of unknown potential makes toxic plants so interesting to scientists, gardeners, and even... horror movie writers.