Wisconsin DNR photo of Giant Hogweed

A possible siting of a noxious and invasive plant, Giant Hogweed, was recently reported in Waupaca County.

A local resident noticed the suspicious plants growing near a bridge on the Little Wolf River in the northeastern part of the county on Saturday, June 13.

Staff from Golden Sands Resource Conservation & Development Council investigated the report and believe the suspect plant to be one of the native look-alikes that grow in Wisconsin.

Giant Hogweed, Heracleum mantegazzianum, is a member of the parsley family and can grow 8-20 feet tall when in flower.

Indicative of its name, this plant produces very large palmate leaves and large white flowers. This tenacious plant can commonly be found near roadsides, stream banks and woodland edges. Giant Hogweed grows very rapidly and can displace many native plant species, negatively effecting biodiversity.

It also produces a toxic sap from the leaves that reacts with sunlight to cause severe burns and blisters on skin.

While Giant Hogweed is a concern for Wisconsin, reports of the plant are often native species that resemble hogweed.

Cow parsnip (Heracleum maximum) and angelica (Angelica atropurpurea) are two plants that are most commonly confused with Giant Hogweed, which bloom around the same time, causing confusion.

When determining whether or not a plant is in fact Giant Hogweed, there are a few key features to look for. Typically Giant Hogweed has 50-150 ray flowers while Cow parsnip and angelica have smaller flower heads with less than 45 ray flowers.

Giant Hogweed also has much larger leaves than either of its native relatives and can span over 5 feet in diameter. The stem of Giant Hogweed is hollow and green, with extensive purple splotches and prominent coarse white hairs.

Angelica will have smooth purple stems, and Cow Parsnip’s stems have no purple splotches and have fine white hairs.

A link to photos of these species can be found at www.goldensandsrcd.org. Area residents who think they have found Giant Hogweed are asked to contact the invasive species coordinator at Golden Sands RC&D Council at 715-343-6215 or [email protected]