Invasive SpeciesGiant hogweed

Heracleum mantegazzianum
FOUND by iSpyaSign
West Falmouth
ID Confirmed
Quality checked by AMD
Peer reviewed by
Field Notes
I was riding my bike along one early summer evening, enjoying the smell of spring and focused on the road beneath my tires, when I glanced from the corner of my eye and caught sight of a very large leafy plant that was huge, but clearly not a rhubarb. It instantly made me think of something I had recently been reading about in the news. I decided to return to the site of my brief sighting, so that I could study the plant more carefully. I couldn't believe how much larger the leaves were, after just one week. I was careful not to touch any parts of the plant, as I read about a toxic sap that can cause blisters upon contact, and wanted to exercise precautions. I picked a rainy evening for my investigation so the amount of daylight was a bit tough so it was hard to get good photographs and my reference materials got wet, but I do think I made an interesting discovery along an innocuous farm road in West Falmouth.
Supporting Evidence
Photo of my evidence.
The leaves were very very large and impressive, about 3 feet across each, and they were lobed with deep incisions.
Photo of my evidence.
The leafs emerged in a cluster pattern, and there was evidence of seedlings germinating at the base of each plant. The stems were hollow, and about 3 inches in diameter.
Photo of my evidence.
The stems were covered in small rigid hairs, and the stems had purple blotches on them.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Heracleum mantegazzianum
Common name:
Giant hogweed
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 43.779500 °
W -70.382820 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
West Falmouth Farms
Trip date: 
Wed, 2010-05-19 18:10
Town or city: 
West Falmouth
Type of investigation: 
Species Survey


I loved your pictures, they were very close and pretty. You really captured the beauty of this rare plant! Great Job! :)

ISpyaSign (or others),
I was wondering if you had a chance to revisit the Hogweed site later on to see what it looks like in late summer. Does it have tall (some 3 meters), brown stalks with upside down umbrella like stalks? There is weird stuff growing up here in Aroostook County with some of the characteristics of Hogweed. If it is in fact Hogweed, the locals should be informed of the dangers. If it isn't Hogweed, I'll stop freaking out for the time being.

Hi there,

I'm so impressed that you recognized such a (thankfully) rare plant! And what a plant it is, too. A friend of mine sent me a link to a YouTube video from British Columbia about Giant Hogweed. In it a professional describes the dangers of the plant's sap and how to remove the plants safely - here's the link:

Looks like you really need to be careful around this plant, and keep little ones away.

Thanks for bringing this species to my attention!

It is really helpful to take the stem shots as they really help with the ID. You do need to break the plant tissue to get sap that may or may not cause a reaction. Brushing up against the plant shouldn’t cause a problem. We have not had a report in Falmouth to date. The closest citing was in Topsham and then one in Buxton I think. We have less than 20 sites reported around the state.

If folks take on trying to control this plant they have to be persistent. It is one of the most difficult plants to control that I have encountered. They will not control it in one season. Also we have a website that needs some updating, but gives folks some basic information.

Good work on the ID!