U.S. Department of Agriculture
Three plant methods for making you miserable.
They jab you with tiny spines, coat you with rash-causing oils or leave a layer of plant juice that causes the sun to burn you.
So what is it with stinging nettles, poison ivy and wild parsnips – why do they hate us?
We don’t know if it’s personal, according to Kelly Kearns at the Wisconsin Department of Natural Resources’ Invasive Plant Program. It may be a defense, as in nettle spines, or a chemical happenstance.
These three noxious weeds cause skin irritations or worse and can turn a pleasant summer outing – or a day of weeding the garden – into a real pain.
Dr. Tom Kunze, an emergency room and urgent care physician for St. Luke’s Hospital in Duluth, says he sees perhaps half a dozen plant-related cases each summer – all from poison ivy – and suspects others use at-home care. He’s seen a few people exposed while doing yard work, but most stumbled into the poison ivy in the wooded or plant-covered areas at Park Point in Duluth or Wisconsin Point in Superior.
The easiest way to deal with these plants is to avoid them, but they don’t come with a Mr. Yuk sticker, so it’s good to familiarize yourself with how they look and where they thrive. “Most people don’t know what poison ivy looks like; even people who are experienced outdoors people,” Tom says.
A simple phrase can help with poison ivy identification: Leaves of three, let it be. Early in the season, the trio of leaves will have a shiny quality.
Poison ivy and stinging nettle are both native to our region.
There are several variations of poison ivy with different growing habitats, Kelly says. You can find it along the edges of woods, in partial sunlight, sometimes even winding up trees. It thrives along trails. Other times it grows on sunny slopes, river shorelines and flood plain areas.
Because it thrives near the Park Point and Wisconsin Point beaches, Tom says, “a lot of times people are in their bathing suits” and have more exposed areas.
The problem with poison ivy is its oil, urushiol, found in all of its parts. Contact with the oil can cause a painful itchy skin rash, an allergic reaction. The skin, which reacts anywhere from 8 hours to 15 days after contact, can develop rashes and blisters. While some lucky people never have an allergic reaction from poison ivy, many do. It can take 10 days to six weeks for the irritation to go away.
As an oil, urushiol can be spread indirectly, too, off pet fur, clothing, sports gear or garden tools in contact with the plant. You can’t get it from touching the rash, since the oil is already absorbed, Tom says.
Those with a large exposure or extreme sensitivity can experience swelling of the face and eyelids, as well as the mouth, neck or genitals. If the plant is being burned, the lungs can be affected by smoke, Kelly says.
“You can see anything from just red, raised areas to blisters,” Tom says. “It can be really on any part of the body, but more usually anywhere exposed – face, hands, arms, legs.”
If you stumble into poison ivy, wash immediately with warm water and soap. You want to get the oil off.
Once you’re clean, then put on gloves and wash everything – shoes, tools, clothes, even the dog if you’ve been hiking together. Oil gets into leather, making shoes a concern.
If you have a reaction, you can use over-the-counter topical itch or cortisone creams, but a more potent prescribed topical or oral steroid may be helpful.
Stinging nettles are another common problem plant. Nettles like a disturbed growing terrain. “Their native habitat is in the floodplains of rivers, where there are natural disturbances of flooding and sediment being deposited,” Kelly says. Unnatural disturbances, like a pile of top soil in a yard, can create habitat.
The pain from nettles is short term, which is why most folks don’t need medical help. The nettle stem and leaves have little “stinging hairs,” Kelly says, that inject compounds into the skin, including histamines. The sting subsides after a few minutes or if rinsed with water, she adds. The stingers, like rose thorns, discourage plant predators.
You can wash the area affected with soap and water. A number of plants also help to alleviate the sting, including jewelweed, which often grows nearby.
While nettles lose their sting, so to speak, by late fall, poison ivy retains its ability to harm all through the winter.
Finally, let’s talk wild parsnips. Parsnips, like carrots, are not native to this continent and were brought here as food for early settlers from Europe. Both went feral here.
Wild parsnip tends to go to seed and dry out by mid- to late July this far north. It thrives in bright sunlit areas, like ditches, which makes it the perfect candidate for being spread as mowers cut and then deliver it farther along the route. “We did not have a lot of it in southern Wisconsin even 20 years ago,” Kelly says.
The yellow-flowered wild parsnip carries a secret weapon – the chemical, furocoumarin, which is produced in all of its living tissue. Furocoumarin sensitizes skin to sunlight, so when it is on skin and exposed to sunlight, it can cause a burn. It can cause redness and blisters similar to poison ivy and so may sometimes be misdiagnosed. It can also discolor or darken the skin in the affected area for as long as two years, some literature says. “It’s not like poison ivy,” says Kelly, “it’s not a rash, it’s an intense burn.”
Some light-skinned, thin-haired animals, like cows, can be affected.
Giant hogweed, found in parts of northeastern Wisconsin and Michigan’s Upper Peninsula, can have a similar effect as wild parsnip.
If you are exposed, wash with soap and water immediately. As with poison ivy, a topical steroid cream may help the burn, as may cool wet cloths.
Besides recognizing and avoiding these plants, you want to take great care to avoid accidental exposure. Be careful off paths or trails.
Wear long-sleeved shirts, long pants and gloves when removing these plants. It’s best to remove wild parsnip just before it flowers (to avoid spreading seeds) and as the sun sets. For nettles, thick pants are necessary.
Also, never, ever – and let me add one more ever – wear shorts while whipping weeds in a densely foliated area.
You could end up covered in wild parsnips, poison ivy or stinging nettles and with a trip for medical help.