<P> Giant hogweed has a stout, bright green stem that is frequently spotted with dark red and hollow red - spotted leaf stalks that produce sturdy bristles . The stems grow to more than 2 m high . The hollow stems vary from 3--8 cm (1.2--3.1 in) in diameter, occasionally up to 10 cm (3.9 in). Each dark red spot on the stem surrounds a hair, and large, coarse white hairs occur at the base of the leaf stalk . The plant has deeply incised compound leaves which grow up to 1--1.7 m (3 ft 3 in--5 ft 7 in) in width . </P> <P> Giant hogweed is a biennial or monocarpic perennial, the plants usually begin dying after they have set seed . It usually flowers in its second year from late spring to midsummer, with numerous white flowers clustered in an umbrella - shaped head that is up to 80 cm (31 in) in diameter across its flat top . The plant produces 1,500 to 100,000 flattened, 1 - centimetre (0.39 in) - long, oval, dry seeds that have a broadly rounded base and broad marginal ridges . Tall dead stems may mark its locations during winter . </P> <P> Giant hogweed was among many foreign plants introduced to Britain in the 19th century as ornamental plants . It is now widespread throughout the British Isles, especially along riverbanks . By forming dense stands, they can displace native plants and reduce wildlife habitats . It has spread in the northeastern and northwestern United States, and southern Canada and is an invasive species in Germany, France, and Belgium, overtaking the local native species, Heracleum sphondylium . Giant hogweed was introduced to the Baltics during the Soviet era as fodder for cattle . </P> <P> In Canada, the plant has been sighted in British Columbia, Alberta, Saskatchewan, Ontario, Quebec, New Brunswick, Nova Scotia, and in isolated areas of Newfoundland . It has been seen in Quebec since the early 1990s . The plant's spread in Ontario began in the southwest and was seen in 2010 in the greater Toronto area and Renfrew County near Ottawa . </P>

Where does giant hogweed grow in the us