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Eco Talk: What to know about giant hogweed in Cayuga County

Eco Talk: What to know about giant hogweed in Cayuga County

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Giant hogweed

Giant hogweed

I was at an event recently that had wildflower bouquets featuring Queen Anne’s lace. I am hopeful that the person creating these bouquets was aware of other plants flowering plants' potential to cause harm.

Giant hogweed (Heracleum mantegazzianum) immediately comes to mind. Giant hogweed, true to its name, can grow to 14 feet or more, has leaves that can grow to 5 feet wide and white flower heads that can grow to over 2 feet in diameter. It prefers sunlight and moist soils, and can be found along water courses and roadsides, as well as fields, forests and yards. Giant hogweed has become newsworthy as more locations are identified and people are exposing themselves to it.

The New York State Department of Environmental Conservation maintains a map, found at, of known locations. Active locations in Cayuga County are found between Cayuga and Owasco Lakes near Ledyard, and along the Lake Ontario shore line.

Giant hogweed and its relatives, wild parsnip (Pastinaca sativa) and cow parsnip (Heracleum maximum), will cause severe skin reactions when any part of the plant is broken. These plants contain a chemical called furanocoumarins, a phototoxin, which reacts with ultraviolet light. If the sap gets on your skin, and is exposed to sunlight, the result is a blistering and itchy rash that takes a long time to heal and can cause scarring. Last year, a friend showed me two-year-old scars, the result of clearing a "weed patch" from his property, not realizing what he was clearing.

Both giant hogweed and wild parsnip are invasive plants. Giant hogweed is native to the Caucasus Mountain region and central Asia between the Black and Caspian seas. It was introduced in the early 1900s as an ornamental plant and has since spread through the U.S. and Canada. It will grow just about anywhere but prefers roadsides, vacant lots, backyards, stream sides, wooded areas and even parks. Wild parsnip, also from Europe and Asia, is now naturalized in North America. It can be found in open fields, along roadsides and any area that has been disturbed.

Cow parsnip is native to North America and grows in woodlands, forest openings and grasslands, and along stream and river edges and roadsides. It, too, contains the phototoxin in its sap that reacts when exposed to sunlight, causing a skin irritation ranging from a mild rash to blistering. Because of its size, growing to 6 feet tall, cow parsnip is often mistaken for giant hogweed. The state DEC’s website has information about all three plants.

If you believe you have found giant hogweed, you can report it the DEC by taking a photo of the entire plant, then individual pictures of the stems, leaves, flowers and seeds, all the while making sure to avoid touching any part of the plant. The collection of pictures can then be emailed to the DEC at, or texted to (518) 320-0309, or call the giant hogweed hotline with the information at (845) 256-3111. You will also want to be able to give directions to the location and estimated number of plants at that location.

Giant hogweed has the potential to spread rapidly because each plant is capable of producing 20,000 seeds in one year, according to Virginia Tech biologist Dr. Jordan Metzgar. Once the seeds mature, they can spread by falling into watercourses and flowing downstream, by the wind, or by human activity such mowing.

One also needs to be aware of poison hemlock (Conium maculatum). It looks similar to giant hogweed; as it can grow to 12 feet tall and has small white flowers growing in clusters that can reach 4 to 8 inches, yet the leaves are very different. It, too, grows along roadsides, in pastures and in ditches, and should not be ingested.

Not all plants with small white flowers are poisonous. Queen Anne’s lace (Daucus carota), also called wild carrot, is native to Europe and Asia, but is now found in North America. It has been used to provide a microclimate for lettuce production and, in some blueberry production areas, is used as a companion crop to attract pollinators. Queen Anne’s lace, however, is considered a serious pasture weed and is listed as a noxious weed in some Midwest states.

Please take time to enjoy the outdoors for the remainder of the summer and into fall. Be aware of your surroundings and vigilant for giant hogweed and its relatives that can cause you and your family harm should you come in contact with them.

Judy Wright is the senior agriculture specialist with Cornell Cooperative Extension of Seneca County. For more information, visit or call (315) 539-9251 ext. 109.


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