Image Credit: "Giant hogweed (close-up)" by Farbenfreude © CC BY-SA 3.0

Avoid the sun like a vampire if you accidentally touch the Giant Hogweed. Hogs and cows may be immune, but humans beware: contact with this nasty plant's sap, along with a dose of sun, may result in purple or black scars, and even blindness.[1][2] With heights up to 20 feet tall this perennial is rightly named a giant. Oddly related to the carrot family, each plant produces approximately 100,000 seeds, a contributing factor on why large colonies of the plant can quickly pop up.[3]