Two native plants, cow parsnip (Heracleum lanatum) and coltsfoot (Petasites palmatus) are sometimes mistaken for giant hogweed, but there are some key differences:
Cow parsnip is smaller
, usually growing to only three to five feet, compared to giant hogweed’s 10 to 15 feet.
The leaves are not so deeply incised and are slightly hairy on the underside.
The purple blotches and fuzzy hairs on the stem are less pronounced on cow parsnip than on giant hogweed.
blooms in early spring and is much smaller than giant hogweed; it has more rounded leaves and smaller
, more rounded flower heads. It is in the composite family.
There are at least thirty giant hogweed sites scattered around Clallam County; many are old homesites.
WHY BE CONCERNED?
Hazardous to humans because skin contact with the sap followed by exposure to sunlight can cause painful burns and permanent scars
Crowds out desirable native plants which supply food and habitat for wildlife.
Giant hogweed is a Class A Weed.
Control is required county-wide.
HANDPULLING can control small infestations
, but the entire root must be dug out or the plant may grow back; care should be taken to avoid skin contact with the sap.
during the growing season will weaken the plant and prevent it from producing seed
, but the roots remain alive for many years when plants are kept from flowering. Known sites should be monitored and mowed as long as plants continue to appear. Avoid skin contact with the sap that may ooze from mown fragments.
Cattle and pigs will eat the plant without ill-effect. Trampling while grazing also discourages growth.
can be effective but should be applied with care. Read the label to check that you are applying an herbicide in the right place, to the right plant
, at the right time, and in the right amount. For perennial weeds
, long term control requires stopping seed production and
attacking the weed’s root system. Translocated herbicides
, (ones that move throughout a plant’s system), such as Roundup (glyphosate) and Crossbow (2,4-D + Triclopyr) are recommended; testing shows that Roundup may provide the best control.
Apply to actively growing plants that are at least 18 inches tall.
Note: Roundup is non-selective
, and will kill target and non-target species alike.
Crossbow targets broadleaf plants without damaging grasses.
Giant hogweed often grows close to water and any herbicide application near or over water requires a permit and a specially licensed applicator.