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.