Unusual plants in the UK — Giant Hogweed

This is the first in a little series I’ll be doing on unusual plants in the UK, where I dive into the lesser-known flora dotting our fields, forests, and gardens.

Plants (like insects and spiders) have always fascinated me. Any chance I get to explore nature (even in the gloom of a UK winter), you’ll find me sneaking peeks at all sorts of trees, leaves, and bushes. It’s always a bonus if I find an insect, but even without seeing a six or eight-legged friend, I love absorbing and observing the patterns plants twist and turn themselves into.

I’m certainly no expert on plants — I just love learning about them, which is partly why I want to start writing about the more unusual plants found here in the UK. In writing and researching these pieces, I get to add to my own knowledge of plants. 

The other reason for writing these, is that I genuinely believe learning about the plants we share this world with is important. Even here in the UK, there is such astonishing variety in the myriad flowers, trees, weeds, and reeds that you could spend a lifetime learning and still discover new facts and folktales.

And, you never know when a bit of plant knowledge could come in handy! Something as simple as knowing dock leaves cancel out stinging nettles, for example, can go a long way. Nature is all about balance and there are few more obvious examples than mitigating the sting of a nettle with the soothing embrace of a dock leaf.

Before I get carried away, let’s begin with the first of my picks for unusual plants in the UK, a plant I spent a lot of time learning to avoid as a kid growing up in Cornwall — the intimidating but fascinating Giant Hogweed.

(Source: iNaturalist. Author: Anastasiia Merkulova)

Giant Hogweed – a bouquet with a bite

Spend any time walking through the countryside in the UK and you’ll almost certainly come across Giant Hogweed, a plant widely known as the nation’s most dangerous. It’s so ubiquitous that if you look at a distribution map of Giant Hogweed, you’ll struggle to find a spot where this striking plant doesn’t grow. 

Oddly enough, the distribution map I found suggested Giant Hogweed was nowhere to be found in Cornwall. I can confirm it absolutely does grow there, and if memory serves, Giant Hogweed is very widespread.

But why is Giant Hogweed considered so dangerous? Within the plant’s stem is a sap containing powerful chemicals (furanocoumarins) that can cause photodermatitis or photosensitivity. This is where the skin becomes extremely sensitive to sunlight and may suffer blistering, pigmentation, and long-lasting scars.

The father of a friend I grew up with was unfortunate enough to fall backwards into a patch of Giant Hogweed, and his entire back was heavily scarred for years afterwards. Trust me when I say, you want to avoid interacting with Giant Hogweed entirely. 

It’s a shame because despite the dangers presented by this plant, Giant Hogweed is quite an attractive plant. The way it bouquets at the top and its tendency to reach heights of three metres or more make it a striking plant to behold.  

Native or invasive?

Giant Hogweed is very much an invasive plant, originating from Russia and making its way to the UK as an ornamental plant in the 19th Century (bet they’re kicking themselves now). It’s since spread like wildfire and can be found pretty much throughout the whole of the UK.

It spreads so effectively because each mature Giant Hogweed plant can produce a mindblowing 50,000 seeds, which themselves can lay dormant for up to 15 years. 

This makes eradicating the plant entirely next to impossible, but it’s still important to limit the spread of Giant Hogweed as best we can. As an invasive species, it’s a threat to local ecosystems and wildlife.

Interestingly, there is a native species of hogweed (Heracleum sphondylium) that you can find around the countryside. While it doesn’t grow as tall nor contain the same furanocoumarins, it’s probably best to err on the side of caution and avoid touching it. 

I personally think this advice should be true for most nature, as we can best enjoy it by leaving it alone to flourish and do its thing! 

Is it safe to remove Giant Hogweed myself?

It’s generally advised get the plant removed by a professional as soon as you can, or yourself but not without covering head to toe in protective gear. Even a small amount of sap can cause lasting damage to skin that’ll leave the affected patch blistering in direct sunlight. 

Giant Hogweed is considered “controlled waste”, so you’ll need to get rid of it at a licensed landfill site. Do not, for the sake of other humans and wildlife, chuck it out with the rest of your garden trimmings.

You should also only remove Giant Hogweed if it’s under one metre in height. Even then, if it’s just under one metre, definitely think about hiring a professional gardener to remove it! Or, you might just trust the removal of Giant Hogweed to nature itself, as Scotland has trialled with grazing sheep. 

If you’re out and about and see Giant Hogweed growing, you should consider contacting your local council. Sadly, one of the most common examples of Giant Hogweed burning is from children touching the plant without knowing how dangerous it is. So if you contact your local council, really stress how important it is to properly remove this invasive species. 

You can also report any Giant Hogweed sightings here (as well as any other invasive species you spot). Here’s a link for people living in Scotland.

What can I replace Giant Hogweed with?

Once the Giant Hogweed is removed, you could always replace it with a native British plant such as an elderberry bush. Unlike Giant Hogweed, elderberry bushes are hugely beneficial to wildlife and their sweet-scented flowers are excellent for pollinators. Plus, you can make delicious elderberry syrup once the berries on the bush mature towards the middle of September.

That’s it for the first in my unusual plants series! Let me know if you’ve had any close encounters with Giant Hogweed yourself in the comments section at the bottom of this page.

If you’re curious, I also wrote a piece on unusual bugs in the UK: