“Plants come up with a lot of different ways to not be eaten,” explained Todd Bittner, the Director of Natural Areas at Cornell Plantations. Chemicals produced by plants are weapons in the arms race between plants and their enemies, especially insects. Some of these chemicals are useful in medicine and other human endeavors. Others can make a plant dangerous to touch.
`When touching something causes rashes or blisters, it’s called contact dermatitis. Plants in our region that irritate the skin include members of the carrot family such as giant hogweed and wild parsnip, poison ivy, poison sumac, spurges, and others.
Giant hogweed, a federal noxious weed, is the worst offender. Described as Queen Anne’s lace on steroids, hogweed has been found in 55 sites in Tompkins County and was the subject of a recent Ithaca Journal article. “I’d take poison ivy over hogweed any day,” said Bittner. Hogweed exposure can cause nasty and painful blisters, scars that may last for years, long-term sensitivity to the sun, and temporary or permanent blindness if the sap contacts the eyes.
Giant hogweed is so hazardous to touch that the New York State Department of Environmental Conservation began a Giant Hogweed Control Program in 2006 to eradicate this invasive plant across the state. Members of the public who spot hogweed are asked to email the DEC or call the giant hogweed hotline at (845) 256-3111. They request detailed directions to the infestation and an estimated of number of plants present. Email photos to firstname.lastname@example.org.
One of the reasons for the DEC program, according to Bittner, is to prevent people from ending up in the hospital from trying to control the plants themselves. Cutting the plant or worse, mowing it, can lead to sap splattering all over. “The people who go out and control it look like Hazmat,” he said.
A hogweed relative called wild parsnip can cause burns similar to hogweed. In both cases, chemicals in the sap cause human skin to be hypersensitive to sunlight, resulting in burns and blisters. Other relatives that cause dermatitis include a native plant called cow parsnip and poison hemlock, famous as the plant that killed Socrates. “I’ve had poison parsnip,” said Bittner, although he said it was milder than hogweed, whose affect he described as ten times worse.
Although less dangerous, wild parsnip is far more widespread. “It’s becoming a real problem,” said Angel Hinickle, a Resource Conservation Specialist with the Tompkins County Soil and Water Conservation District. “I see it a lot on the roadsides.” Wild parsnip is an invasive plant with flat-topped yellow flower clusters. Like giant hogweed, it produces large numbers of seeds and spreads easily. Unlike hogweed, there is no program attempting to eradicate wild parsnip from New York state.
Eradication is an unusual goal. No one is trying to eradicate poison ivy, a native plant, from Tompkins County. “You will typically find it in areas that have been disturbed,” said Hinickle, including roadsides. There is a lot around, especially near the Fuertes Bird Sanctuary next to Stewart Park. “They have a ton in there,” she said.
Poison ivy causes an allergic rash. Urushiol oil, the allergen, is present in related plants like poison sumac, a rare wetland dweller, and poison oak, which is found further to the south and west. Because it is an allergy, different people may react differently to exposure and worse reactions may develop over time. Dangers include secondary infections and internal problems from burned or ingested poison ivy. Other animals are more fortunate. The oil does not hurt them, allowing wildlife to utilize this native plant as an important food source.
“We don’t necessarily look for poison ivy,” said Jeff Payne, the manager of facilities at the Cornell Laboratory of Ornithology. He thinks most people know enough not to touch it. “If we happen to notice it, we do cut it back,” he said, but only if it is in a place where it will affect people. Since the poison ivy will grow back from cutting, more permanent control generally requires herbicides. Payne said that in the rare cases when herbicides are used, they don’t apply the herbicides themselves and everything is strictly documented. One place where they’ve had to use this treatment is the feeder garden, where there is a lot of plant growth and people are frequently walking through to replenish the bird food.
Other skin irritants include nettles, the milky sap of some spurges, and prickly plants. Hikers and gardeners, beware.