Recently a video was making the rounds on Facebook about the effects wild parsnip (Pastinaca sativa) had on a person exposed to it.
Wild parsnip is native to Europe and Asia and has become common in many parts of the United States including northern Wisconsin. When combined with sunlight, the sap of this plant causes a reaction called phytophotodermatitis. The rash that develops is painful can result in blistering similar to a second-degree burn. Exposure to the sap occurs when the stems and leaves are broken.
Wild parsnip is a biennial. The plant grows foliage the first year and in the second produces a yellow inflorescence. Second-year plants can be two to five feet tall. Wild parsnip is commonly found along road sides or in unmanaged fields. It can be identified by the yellow flowers or the leaves. The leaves of wild parsnip are compound with approximately five to fifteen oval leaflets. In the first year, the leaves form a rosette, while in the second year leaves are present on the flowering stems.
Due to possible toxicity, it is best to take pictures of the plant if you are not sure if it is wild parsnip and avoid picking the suspected plants. I prefer to be extra cautious and refrain from touching the plants. There are some other plants that look similar to wild parsnip. Golden Alexanders (Zizia aurea) and prairie parsley (Polytaenia nuttallii) are two plants that have flowers and foliage that look similar to wild parsnip. Prairie parsley is considered a threatened plant and is not common in the northern part of the state.
The best way to control wild parsnip is early in the season with a systemic herbicide. Systemic herbicides move throughout the plant and kill all of the plant parts. When using any pesticide, it is important to read, understand, and follow instructions on the label.
After reading this, you might be wondering how it is possible for a plant to be worse than wild parsnip. There is another plant that is even nastier — giant hogweed (Heracleum mantegazzianum) which is related to wild parsnip. There have been confirmed cases of giant hogweed in Wisconsin, the closest being in Iron County.
Like wild parsnip, the sap from giant hogweed reacts with sunlight and causes burns. It may cause temporary or permanent blindness. The sap can also spatter when the stem is cut by a weed whip or other means. As the name implies, giant hogweed is a big plant, it can be eight to 20 feet tall. Giant hogweed looks similar to cow parsnip (Heracleum maximum). The primary difference between the two plants is that giant hogweed is usually much bigger and has purple blotches on the stem.
If you are uncertain on the identification of the plant take pictures and avoid any contact.