Cow Parsnip - Heracleum maximum
Cow parsnip is native to North America. It is a HUGE plant that grows to be over 2 meters (7 ft) tall. The flower umbels are 20 cm across and the leaves are up to 40 cm across! It is often confused with Giant Hogweed (Heracleum mantegazzianum), but cow parsnip is not as toxic. Cow Parsnip sap contains a phototoxin that reacts with ultraviolet light to cause skin irritation ranging from a mild rash to severe blistering. It's kind of like an anti-sunscreen.
''Heracleum maximum'', cow parsnip is the only member of the genus ''Heracleum'' native to North America. Its classification has caused some difficulty, with recent authoritative sources referring to it variously as ''Heracleum maximum'' or ''Heracleum lanatum '', as ''H. linatum'', or as either a subspecies, ''H. sphondylium'' subsp. ''montanum'', or a variety, ''H. sphondylium'' var. ''linatum'', of the common hogweed . The classification given here follows ITIS.