Identification

Giant hogweed may be mistaken with other species of the same family (purple-stemmed angelica, wild parsnip), but most often with American cow parsnip (Heracleum maximum). The American cow parsnip is a native plant which grows naturally in Quebec. This native plant is widespread across the eastern province. It does not require any particular control measures. Certain people may develop dermatitis following contact with the sap of the American cow parsnip, but the burns are generally much less severe and less painful than those caused by giant hogweed. Nonethless, caution must be used, and protective clothing is recommended when manipulating American cow parsnip.

In order to avoid undertaking expensive and unnecessary eradication measures, it is important to ensure that the plant in question is in fact giant hogweed. Three criteria are used to easily distinguish between these two species.

Pictures : H. Royer and E. Groeneveld

SIZE : Giant hogweed is much taller (4 to 5 m), at maturity, than American cow parsnip (2 to 3 m). Of course, plants which were recently cut down or which have not yet reached maturity (normally between 3 to 5 years), may be shorter.

Pictures : H. Royer and E. Groeneveld

STEM : Giant hogweed has a stem with red blotches or speckles. The stem of American cow parsnip is all green (sometimes with purple), but does not have the red spots or speckles. Also, the stem of giant hogweed has scattered coarse hairs. The stem of American cow parsnip is covered with velvety fine hairs.

Pictures : H. Royer and N. Blanchette-Forget

Pictures : H. Royer and E. Groeneveld

LEAVES : The leaves of giant hogweed are huge (sometimes 1 m across at the base of the plant) and highly dissected. There are no hairs on the underside of the leaf. The leaves of American cow parsnip are much smaller and less dissected. The underside of the leaf is entirely covered with fine hairs which form a downy layer.