Titia is interested in photography, poetry, family, art, dogs, cats, insects, wildlife, history, war, camping, writing, and the environment.
What Is Giant Hogweed
Giant Hogweed (Heracleum mantegazzianum) originates from the Caucasian mountain in Asia. In its native habitat it can reach a height of 2,5-5 meters (8-15ft). It's a perennial plant and it can live for years when left alone.
In the 19th century they introduced it in Europe as well as in Canada and the USA as an ornamental in big gardens. In the Netherlands the average height of this plant reaches about 3 meters (10ft)
You Should Treat Giant Hogweed with Respect
The stems of the giant hogweed are about 3-8 cm 1.2"-3.1") in diameter, sometimes even 10cm (3.9"). The stem has purple pigmentation and white hairs on raised nodules. The sap of the plant is photo-toxic. This means it can burn your skin when you touch the plant, no matter what part. The flower head is umbrella shaped. It's formed by tiny white flowers and it can produce up to 100.000 1cm flattened seeds per flower. Never touch this plant with your bare hands or other bare parts of your body. When you want to pick a flower, wear gloves and cover your arms.
Giant Hogwood Seeds - Don't Spread Them
The hogweed produces thousands of seeds per plant. It is not wise to let these seeds spread by wind or let them fall to the ground. The main umbel in the middle will bloom first, followed by smaller umbels around it. The seeds are oval shaped and flattened. Whenever an umbel goes into seed, cut it down and keep them in a bin. When they're dried burn them. Don't throw them on your compost heap, because they will germinate, even after many years.
Giant Hogweed Is an Invasive Species
Definition of Invasive:
Tending to spread widely in a habitat or ecosystem.
Official U.S. definitions about invasive species provided in Executive Order 13112. Signed by President William Clinton on February 3, 1999:
"Invasive species" are alien species. Their introduction can cause economic or environmental harm or harm to human health".
In other words: it's not native in the area it grows in. It spreads around in an aggressive way and it's ousting the local native species.
The NY State Department of Environmental Conservation calls it:
"A Federally listed noxious weed".
That's exactly what this plant does in some parts of the countries it has invaded. A full grown Hogweed can produce thousands of seeds each year. The seeds are spread by wind and birds. A single Hogweed won't stay single. The fallen seeds will germinate and form a tapestry of seedlings.
Be Very Careful Around Giant Hogweed
The sap of the Giant Hogweed plant is phototoxic. Phototoxicity is a chemical induced skin irritation. In close collaboration with sunlight it can cause Phytophotodermatitis. This is an inflammatory reaction of the skin, like a very sever sunburn. The inflammation can last for days or weeks. It can leave permanent damage to the skin.
What You Should Do When Handling Giant Hogweed:
- Don't touch Giant Hogweed with bare parts of your skin
- If you have to touch it, wear gloves and cover your arms and legs
- Handle with great caution
What You Should Do When You've Touched Giant Hogweed:
- Immediately wash the affected area with soap and water
- Avoid further exposure to sunlight at least for 48 hours
- Go to a doctor for further treatment
It Takes Time and Effort to Keep This Plant Under Control
Well, to tell you the truth, it's not easy to control this plant. There are many methods and each country where this invasive plant is growing has set its own rules. You can find them all when clicking the links in this article or through your own search on Google. So I won't give you all the specifics here. I'll just tell you what I do to keep it under control.
First of all I get rid of most of the seeds when they're still on the plant. I tried to pull out the tiny seedlings, but as there are so many, it will take a lot of time, so I don't do that anymore. I run them over with the lawn mower. When they're already a bit bigger, you won't be able to pull them out. You might get the leaves, but you won't get the heart and it will continue to grow. The hogweed is a perennial plant. This means that the same plant will appear each year on pretty well the same spot as the year before. So as I can't pull them out, I cut them as short as possible. They will wear themselves out in the end. Or I use a spade to get the root out.
Of course you can kill them with pesticides, but then you will kill a lot of other harmless native plants too. Besides in most countries the use of harmful pesticides is decreasing.
Sheep, Goats, and Pigs in Combat with Giant Hogweed
In the Netherlands we use sheep, goats, and pigs to limit the spreading of the Giant Hogweed in nature reserved areas. They love to eat the plant and unlike humans, the plant doesn't harm them. The videos below show what these animals do with Giant Hogweed.
Of course the Netherlands is a rather small country in comparison to Canada or the USA. So the invaded areas are smaller too. Even so the sheep, goats and pigs help to decrease the plant's invasion. This method is also environmental friendly.
Pigs Eating Hogweed
This 'pig' video needs some explanation because it's Dutch spoken. These are Duroc pigs and the owner tells us that they love to eat hogweed. The pigs are still young, but when they're grown up they can dig deeper and will eat all the roots too.
An Ode to the Heracleum Mantegazzianum
Last but not least a small ode to this invasive yet beautiful majestic plant. Made by a country fellow. It shows exactly why I'm in love with the giant hogweed, despite the fact that it has a nasty habit,. It needs no words, the images speak for themselves.
Links to Informative Hogweed Websites
- King County Noxious Weed Control Program
Giant hogweed is a Class A Noxious Weed
- Ontario Weeds: Giant hogweed
Very interesting website with lots of information.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2012 Titia Geertman
Love to Read Your Comments
Barbara Badder from USA on May 16, 2017:
A doctor told me that this plant is used for the production of Bentyl. That is a drug used to treat IBS. I think we had these on our farm back when I was a kid.
Tony Bonura from Tickfaw, Louisiana on February 17, 2013:
I had never heard of this plant before. Thanks for a very informative lens. Those burns look really bad. I hope it doesn't get you!.
editionh on May 10, 2012:
Hi Titia, your lens is a great resource for people who want to learn about the giant Hogweed.
As far as I understand Hogweed can burn you only when your skin is wet ?
Is that true or will it burn my skin in any case?