Cow Parsnip

The juices of all parts contain a phototoxin that can act on contact with skin and exposure to ultraviolet light, causing anything from a mild rash to a blistering, severe dermatitis, depending on the sensitivity of the individual. The plant is a pernicious weed especially in pastures, where it can ruin the milk of cows that eat it. Various Native American peoples had many different uses for this plant; all parts of it were used by one nation or another. Perhaps the most common use was to make poultices to be applied to bruises or sores. In addition, the young stalks and leaf stems — before the plant reaches maturity — were widely used for food with the outer skin peeled off giving a sweetish flavor. The dried stems were also used as drinking straws for the old or infirm, and to make flutes for children. A yellow dye can be made from the roots, and an infusion of the flowers can be rubbed on the body to repel flies and mosquitoes.
Wikipedia