Don’t get burned by invasive species in St. Lawrence County
Sunday, July 6, 2014 - 5:29 pm


It’s that time of year again when we try to avoid getting sunburned, avoid burning meat on the grill and avoid getting burned by parsnips.

Wild parsnip, an invasive plant that has spread rapidly throughout northern New York in recent years, can cause severe chemical burns if its sap contacts your skin, and this is peak season for it.

A member of the carrot family, wild parsnip is related to Queen Anne’s lace, and has a similar “umbrella” flower cluster, although it’s a dull yellow-green color rather than white. Wild parsnip grows three to six feet tall and has leaves reminiscent of celery or Italian parsley leaves. It’s usually a biennial, with the flower stalk produced in the second year. In some conditions it may require two or more years to mature, but it’s not a perennial.

In most of our region wild parsnip has begun to flower and is much more visible than it was just two weeks ago. It can be found in vacant lots and ditches as well as in yards and gardens, but because it’s so effectively spread by mowing equipment, mile after mile of wild parsnip can be seen along our roadways.

The root of wild parsnip is in fact edible. Its sap, though, like that of a related invasive species, giant hogweed, is “phytophototoxic.” In the words of David J. Egan of Wisconsin’s Department of Natural Resources, “That means an inflammation (itis) of the skin (derm) induced by a plant (phyto) with the help of sunlight (photo).”

Wild parsnip juice on one’s skin—or in one’s eyes—reacts with sunlight to cause severe burns. And by severe I mean blisters that can take months to heal, and which may leave permanent scars. In the eyes, the sap can cause blindness.

It’s a small consolation, but unlike poison ivy, wild parsnip won’t cause symptoms if you merely brush up against it; the stem has to be broken or crushed to release its sap. Also, once it’s dry it poses no threat, which is definitely not the case with poison ivy, which is “as good as new” after it has been dead and crispy for months. Dry wild parsnip plants can be handled or burned without posing any danger.

As everyone knows, when fighting zombies, grab a shovel and aim for its head. The same with wild parsnip, except you aim for its feet. It has a taproot that’s very hard to pull out, but which is easily cut with a shovel. It’s not necessary to get the whole root; just dig as deep as you can to sever the taproot, pry up and the plant will die. You don’t even have to touch it.

If you’re hopelessly outnumbered by wild parsnips, at least mow them now as they begin to flower. This will temporarily keep them from making seeds while you muster some shovel-wielding townsfolk (pitchforks and torches are optional) to help you. Wear protective clothing when mowing wild parsnip, even on a tractor. And unless you’re in a Level-A hazmat suit, don’t use a string trimmer on it.

Glyphosate, the active ingredient in herbicides like Roundup, kills wild parsnip. Herbicide is most effective when used on first-year plants (“rosettes”), ones which have no flower stalk, in late summer or early fall. Spraying early in the season may kill the top only, but not the root.

For a healthier, happier summer, wear sunscreen, carry barbeque sauce and watch out for wild parsnip.

Paul Hetzler is a horticulturalist at Cornell Cooperative Extension of St. Lawrence County.