Giant Hogweed: a plant whose sap may cause painful burns, scarring, and blindness in some cases if contact with the eyes occurs. The scientific name for giant hogweed is Heracleum mantegazzianum. Other names for this plant have included cartwheel-flower, giant cow parsnip, hogsbane, or giant cow parsley. Giant hogweed can grow tall, reaching up to 14 feet in height after a few years. After 3-5 years of growth, the plant produces large white flowers one to two feet across, as well as five-foot-wide jagged and lobed leaves. Chemicals in the sap known as furanocoumarins cause the severe burns when exposed to UV light from the sun, a process known as phototoxicity. Painful blisters form within 48 hours of exposure to the sap in the presence of sunlight. Giant hogweed was introduced to the US in the early 20th century.
REFERENCE: Jegede, TJ, MD, et al. Phytophtotoxin Poisoning. Updated: Apr 20, 2015.