Those swaying plants with the yellow flowers you see along roadsides or maybe even on your property this time of year may look benign, but they could be dangerous if what you're seeing is wild parsnip. Also referred to as "poison parsnip," the Vermont Department of Health and Agency of Agriculture recently sent out a warning to Vermonters that the sap from this plant can cause severe skin reactions.
Tim Schmalz, plant pathologist with the Agency of Agriculture, told Vermont Edition more about this plant and how to avoid being harmed by it.
About the plant
"It's a biennial, so it has typically a two-summer growing season," Schmalz explains. "The first year is when the seed germinates and it establishes a strong taproot, which is very similar to the parsnip that you're familiar with seeing in the grocery store."
After the first summer, the aboveground leaves die while the taproot remains, Schmalz explains. It's in the second season that the familiar yellow flowers appear on the tall stems. Wild parsnip flowers resemble Queen Anne's lace, in shape. And it turns out that's no coincidence.
"It's actually the first cousin to Queen Anne's lace," Schmalz explains. "So that's an apt description that it has that sort of inverted umbrella shape or an umbrella shape, so a central stem and then lots of very small flowers coming out of a central point."
Why it can be dangerous
Schmalz explains that many plants in the parsnip family contain furocoumarins, chemicals that when combined with skin and ultraviolet light can cause what's known as a phytophotodermatitis.
"It can result in very uncomfortable rashes and blisters – not at all unlike a second-degree burn from fire or a heat source," Schmalz says about poison parsnip's effects on the skin. "It is a serious reaction in most cases."
But unlike reactions to poison ivy or poison oak, Schmalz explains, brushing up against wild parsnip won't generally cause a problem.
"In most cases what has to happen is that the sap within the plant, the juices in the plant, have to come in contact with your skin," Schmalz says. "So you'd have to damage the plant in some way or break the stem or rub the sap up against you, up against your skin. And then on top of that, in order for the reaction to complete, you typically need to have some kind of reaction occurring as a result of ultraviolet light contacting that sap on your skin."
That kind of interaction can happen if you pick the plant by hand or are weed whacking and get pieces of the plant on your exposed skin and if that skin is then exposed to sunlight. So people should take precautions when working with these plants. Wear gloves, safety glasses, long sleeves and boots. Pick a cloudy day to handle the plant, if you can. And if you do get the sap on your skin, the Vermont Department of Health recommends washing the sap off immediately and then wearing clothes that prevent exposure to the sun for another 48 hours.
"And then obviously if you do see a reaction on your skin, [it's] probably a good idea to talk to a doctor about what the best approach to managing that reaction would be," Schmalz adds.
Managing the plant
To manage poison parsnip on your property, Schmalz says you can mow the plant or use herbicides, though he cautions that you should mow before the flowers have gone to seed. If you see the flowers setting seed, bag them up so the seeds don't get into the soil. He also explains that most of the herbicides that are out there for poison parsnip control are best used in the spring or fall.
Lastly, Schmalz cautions not to get discouraged if it seems like you aren't making progress in initial efforts to beat back the plant. Once poison parsnip is established on your property, there's a seed bank in the soil, so new plants will likely continue to emerge for up to five years.
Wild parsnip is an invasive species and its prevalence on the landscape has been on the increase over the last two decades. Schmalz says he hopes the plant will find an equilibrium, but at this point he can't predict.
"It remains to be seen what happens with parsnip," Schmalz says. "If it becomes the plant that ate New England or if it just becomes a sort of a presence in the landscape that we just learn to live with but that it doesn't take over."