Giant Hogweed Resources

Click Here to Access OSU Extension's FactSheet on Giant Hogweed      

Click Here to Access OSU Extension's Ornamental Circular on Giant Hogweed 

Click Here to Access Pennsylvania's Brochure on Giant Hogweed 

Click Here for a Free Downloadable Poster Developed by OSU Extension

Read More about Giant Hogweed in Ashtabula County

Each year we encounter new diseases, weeds, and insects that we must identify and determine their threat level. Farmers and homeowners alike are getting more familiar with such recent pests as the Soybean Aphids and Multi-colored Lady Asian Beetles. Recently, a new invasive weed pest emerged in northeast Ohio; this being Giant Hogweed. Please read on as you may have stumbled upon this weed.

This new plant is Heracleum mantegazzianum better known as Giant Hogweed. This huge plant is a member of the carrot or parlsey family and was introduced into Europe and North America in the early 1900s. This plant is most easily identified by its large clusters of small flowers that appear around the beginning of July. These flowers cluster together to form a topped umbrella shape that can span close to three feet across. This plant can grow up to fifteen feet in height and have a four inch stem. Its hollow stem has distinct purple blotches with coarse white hairs that circle the stem at the base of the leaf stalks.

The leaves are lobed, deeply incised and can measure up to five feet across. This plant's name comes from Hercules of ancient mythology. Because of its massive size and appearance, this plant was cultivated and transferred between many arboretums and personal gardens. Unfortunately, this plant has spread from these gardens and has become established in roadside ditches, stream banks, vacant farmland, and along tree lines.

In the United States , it is known to occur in eleven states and is now listed as a Federal Noxious Weed making it unlawful to propagate, sell or transport. Our neighbors in Pennsylvania have become the hot spot for this weed. In fact, our neighboring Pennsylvania counties, Erie and Crawford, each have over 100 sites where this plant has been identified.   To date, Giant Hogweed has been spotted in Andover , Austinburg, and Jefferson Townships and in the heart of Ashtabula Harbor (in Ashtabula County).

So what is the hazard of this plant? This plant is a public health issue because of its potential to cause severe skin irritation. This plant causes painful, burning blisters within one to two days of contact. These purplish or brownish scars can persist for several years. 

So what can we do to help? The USDA-APHIS office is requesting you check your property for Giant Hogweed. Many folks confuse this plant with cow parsnip ( Heracleum lanatum ), Angelica ( Angelica atropurpurea ) or Poison Hemlock ( Conium maculatum ). You are cautioned about mowing, cutting or weed wacking this plant as its large taproot will soon send up new growth. Additionally, it will place you in risk of coming in contact with the plant's sap. To learn more abotu Giant Hogweed, please access the following factsheet: