Giant Hogweed (Heracleum mantegazzianum) is a plant in the family Apiaceae. This is the Carrot and Celery family, sometimes known as the Umbellifers. Most of you will probably be familiar with Queen Anne’s Lace / Wild Carrot (Daucus carota) as being a common weed in suburban gardens, I know I’m continually weeding it out of my flower beds.
ID sheet, Giant Hogweed height comparison, stem markings, and colony on a riverbank.
Giant Hogweed was introduced to the USA from Asia as a garden ornamental, prized for its size and architectural form. It is now semi-established in the wild in a number of states, although it is still not widespread as it is in Europe.
Many of you may have seen reports recently that “Hogweed can cause 3rd degree burns and permanent blindness”. E.g. https://www.cbsnews.com/news/giant-hogweed-plant-causes-blindness-third-degree-burns-discovered-in-virginia-other-states/
Before I get into why I think such reports are overhyped, lets talk about why Hogweed can be dangerous. Many plants in the Apiaceae (and some plants in the Fabaceae etc) contain a group of chemicals known as Furanocoumarins. These can, when applied to the skin cause what is known as Phytophotodermatitis. Put simply it greatly inhibits the skins ability to block sunlight, thus resulting in what is essentially very bad sunburn.
OK, so now we know what the issue is, lets go over why I think the fearmongering around this plant is a bad idea, and why the dangers have been over hyped.
Hogweed is not the only plant that causes these issues.
Giant Hogweed is one of several member of the Apiaceae which can occur in the wild in the USA which contain significant levels of Furanocoumarins. Most commonly you will hear about Wild Parsnip (Pastinaca sativa) which has similar levels of the chemical, and can cause burns. This plant is super abundant, occurs across a wide range, and grows to a height that is easy to come into contact with when hiking in shorts for example. In fact I have known gardeners to develop rashes of this nature from garden planted parsnips.
Wild Parsnip – Also phototoxic.
It’s very uncommon.
Giant Hogweed occurs in less than a 3rd of states, and in most states it is confined to a few locations in one or a handful of counties. In the state in which I live, Wisconsin, there are few records, and it is limited to 6 out of our 72 counties. It is of course entirely absent from some areas such as the great plains and the south.
Having grown up in the UK, where the plant is much, much more common, I have to say I have not once spotted it in my travels in the USA so far, and I am very familiar with it so it would be immediately apparent. In the UK I would encounter it regularly, and even then reported cases of exposure were rare.
The chances of you coming across it are very low, and the chances of you being accidentally exposed even less so.
If you think you’ve found Giant Hogweed, it’s most likely it’s native relative Cow Parsnip (Heracleum maximum).
The map is slightly outdated, but is fairly close to the current picture, and shows that it is not very widespread. In many of those counties it has only been found in 1 location.
It’s generally not THAT bad.
Whilst it’s undoubtedly true that the plant in question can in some cases cause significant injury, there are few cases of severe burns causing lasting damage, and most severe exposure comes from people attempting to clear the plant by hand, or by using mowers or weed whackers on it which will cause more sap to fly around and land on skin etc.
Most cases of exposure, such as rubbing against the plant whilst walking will cause rashes similar to Wild parsnip, which as we have discussed is far more commonly encountered.
If you are exposed, recognizing the plant can allow you to wash off any sap asap and apply sunscreen to the area which can help prevent or mitigate any symptoms.
It is also worth noting that many garden plants can cause skin irritation, or are extremely poisonous if ingested, and pose more of a risk to human health than a rare, wild plant.
It’s not going to make you go blind
I have not encountered any actual case where someone has been blinded by sap from Giant Hogweed. Is it theoretically possible? Erm I guess, maybe, if you took a bunch of it, mashed it up and rubbed it in your eyes and left it there, sure, maybe. But the same would be true of, I don’t know, most things in your house, and sand, glass etc.
Hey kids, don’t rub weird plant juice (or anything) in your eyes and you’ll be good.
Its colossal size makes it easy to identify.
Many people at the moment are mistaking all sorts of similar looking plants for Giant Hogweed, caused by the panic from such articles linked above. However its very easy to recognize the plant by its sheer scale. It is twice as tall as its nearest look alike with leaves twice as big or more. The same is true for stem thickness and flower size etc.
If you come across a 10-15ft tall plant that looks like it landed here from another world, are you going to go and rub it all over yourself? I didn’t think so.
Hogweed 10+ feet tall with leaves 3+ feet long.
The panic is damaging the environment.
This is a very real problem. Before I moved to the states I had been battling the Hogweed hysteria in the UK for a number of years. In that time I have personally, and by way of the internet foraging/plant groups, seen numerous occasions where valuable and important native plants, which bear passing resemblance to Giant Hogweed being pulled out, mown down, or poisoned with chemicals because of mistaken identity. Indeed even where Hogweed itself is sprayed it will poison other native plants in the area.
Spraying Hogweed with herbicide, note the other native plants in the foreground.
The fact that most people have very little plant knowledge, coupled with some of the similarities of many plants in this genus make the problem worse. On top of that with the plant being so uncommon in the USA most Americans have no personal experience with the plant and hence are bad at identifying it.
This is borne out by a recent post originating from the Virginia DNR citing the presence of Giant Hogweed at a particular park in their state. The photo that accompanied the message was of the native and ecologically important Cow Parsnip, and not Giant Hogweed. When a DNR can’t even get it right, it’s easy to see how misinformation is easily spread.
In summary, Giant Hogweed is really no more dangerous than any number of other plants, and you are far less likely to ever encounter it.
As with all things in the media there is a lot of hype, and a little bit of hysteria, theres a little bit of the “immigrant plants coming over here burning our kids” going on.
Rather than creating more panic, simply take some time to become more familiar with plants in this family, and avoid contact with them on sunny days if you are concerned.
I would also advise wearing long pants when hiking. Not only will this protect you from low growing Wild Parsnip and Poison Ivy etc, It will also help keep ticks from biting you, which are a far more dangerous issue than any wild plant I care to mention.
If you think you have found giant hogweed, feel free to email me at firstname.lastname@example.org and I can confirm or correct the ID from a photograph.
Thanks for reading, stay safe and happy foraging!
Eden Wild Food