Worse than poison ivy: How to identify, report dangerous hogweed plant found in Michigan

Giant hogweed plant.
Giant hogweed plant.

Giant Hogweed has been found in counties around Michigan in recent years.

Funding to support the detection, identification, or control of Giant Hogweed is no longer available to the Michigan Department of Agriculture and Rural Development, which means it's up to residents to report and manage the dangerous plants.

Related: 11 invasive species to watch out for in Michigan

According to EDDMapS, hogweed has been reported in several counties, including Oakland, Saginaw, Jackson, Branch, Calhoun, Eaton, Kent and Muskegon counties.

Here's some info on hogweed from MDARD:

Where does it come from?

Giant Hogweed was introduced into North America in the early 1900s. Its native range is Central Asia, although now it occurs throughout the United Kingdom, Australia, Europe, parts of Canada and the United States. It is suspected to have made its way into this country as an ornamental. Its size made it somewhat of an oddity and gardeners that wanted something unique imported it.

What's the risk to humans?

Giant Hogweed is a public health hazard that ranks up there higher than poison ivy, poison oak and poison sumac in respect to its potential to harm humans. The reason for concern is that the sap from this plant can cause a severe skin reaction known as photo-dermatitis or photo-sensitivity. The reaction can happen up to 48 hours after contact.

After coming in contact with the sap, the skin blisters when exposed to sunlight. Contact with the eyes can lead to temporary or possibly permanent blindness. The weed can be especially troublesome for children that may find the long stems attractive to play with.

If you do come into contact with the plant, and especially the sap, you are advised to wash the affected areas immediately, keep the exposed area out of direct sunlight and seek medical advice.

Related: Venomous brown recluse spider found in 10 Michigan counties: What to know

How to identify

Proper identification is an important first step. A number of common plant species resemble Giant Hogweed, but there are ways to tell them from the real thing. Only approximately 2% of suspect plants submitted to MDARD for identification are confirmed as Giant Hogweed.

Some characteristics:

  • White flowers with 50-150 flower rays clustered into an umbrella shaped flower cluster up to 2.5 feet across
  • Between 7 and 14 feet tall (depending upon growth stage and if mowed or cut)
  • Huge leaves, incised and deeply lobed up to 5 feet across
  • Stems are green with extensive purple splotches and prominent coarse white hairs. Stems are also hollow, ridged, 2-4 inches in diameter, and have a thick circle of hairs at base of leaf stalk
  • Seeds are dry, flattened, and oval. Approximately 3/8 inch long and tan with brown lines (oil tubes) extending 3/4 of the seed length that widen at ends

Many plants are often misidentified as giant hogweed - the most common plant being cow parsnip. Please thoroughly look through the charts below to see the major differences between giant hogweed and cow parsnip, angelica, wild parsnip, and poison hemlock.

The video below describes how to properly identify hogweed:

How to report or ask for help

If you have seen a plant that appears to be Giant Hogweed and need help identifying it, send an email to MDA-Info@Michigan.gov, along with any pictures, so that it can be examined by professional staff of MDARD. (Please e-mail four pictures:  1. Whole plant, 2. Leaf, 3. Flower/seed head, 4. Where a leaf joins the stem.)

Here’s an info sheet from USDA on Giant Hogweed:

About the Author:

Ken Haddad is the digital special projects manager for WDIV / ClickOnDetroit.com. He also authors the Morning Report Newsletter and various other newsletters. He's been with WDIV since 2013.