Wednesday, May 26, 2010

I'm an alien I'm a legal alien, I'm a Gunnera in West Cork

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Well without trying to upset anybody, I have to admit that Gunnera is one of my favourite perennial plants. This might be upsetting for some as there are people out there with a very strong opinion about them, but I will talk about that later on in the post. First I want to talk about the plant itself.

Gunnera is believed by some to be poisons, I even remember hearing this when I was young. So far I can not find anything to back that up, and it is not listed in the RHS toxic plant list.
Gunnera is a common sight in Ireland, however it is in fact an alien species and is actually a native to Chile and Argentina. There are two main varieties in Ireland Gunnera tinctoria and Gunnera manicata. It is important not to confuse them, Gunnera manicata is the most common one sold in garden centres where as Gunnera tinctoria is the one often found in the wild and has become very invasive and is hated and feared by many in the west of Ireland.

The one I have photographed here is the Gunnera manicata also known as Giant Rhubarb or Dinosaur Food.

This impressive deciduous perennial will eventually produce huge displays of massive dark green lobed foliage, so you need plenty of space! The architectural leaves grow up to 6 feet across. They are rounded and deeply toothed, and sit atop prickly stalks that extend to 10 feet tall and form giant clumps. Gunnera manicata produces large, bottle-brush spikes of tiny reddish-green florets in the spring. It looks best planted near water in an informal semi natural setting.

An established Gunnera manicata can grow amazingly quickly in the spring as the shoots appear from the crown, this is one reason why they need to grow in a moist soil full or organic matter to supply a steady supply of water to fuel such a high rate of growth. On a warm spring day you can watch the amazing growth of a Gunnera over just a few hours as the leaves unfold and the stems extend and its gigantic green leaves spared out, creating fantastic solar collectors. The leaves’ undersides are also covered with spikes, as are the leaf stalks. The upper surface of each leaf is heavily textured, and the leaf’s contoured shape serves to catch and channel water to the plant’s roots.

At the macro-/microscopic level, when growing in nitrogen deficient soil, Gunnera manicata plants develop stem glands. The plants then form a symbiotic relationship with a nitrogen-fixing Cyanobacteria (Nostoc punctiforme). The bacteria enter the plant through these stem glands found at the bases of leaf stalks and then trigger an intracellular symbiosis, giving the plant fixed nitrogen in return for taking some of its fixed carbon for the bacteria’s metabolism. This “in-between-plant-cells interaction” is unique in higher plants, and may help plant scientists initiate novel symbioses between crop plants and cyanobacteria—allowing specific plants to grow in areas lacking fixed nitrogen in the soil. At present, Gunnera is the only genus of angiosperms (flowering plants) known to host Cyanobacteria (formerly called Blue-Green Algae)

The Alien Invasion

So the other day when on an Irish gardeners forum, I came across a question posted by a user on When is the best time to cut the leaves off a Gunnera to place over the crown to protect from frost? (Best just to fold the dead leaves over the crown, if you are wondering)

What amazed me was some of the replies he got. He was told by one user that Gunnera is an invasive species and that he should remove and destroy the plants he has immediately. Another person wanted to know why the Dept. of Agriculture does not demand licences for having them on a premises. Well I could give you some more examples, but I think it is safe to say that there are some strong opinions out there. So before people start declaring all out war on the Gunnera, it needs to be said that it is the Gunnera tinctoria that is the invasive variety and not the larger Gunnera manicata.

This is of course an easy mistake to make when you see pictures like this.

The Gunnera tinctoria is however becoming a serious problem for many people in the milder west cost of Ireland and there are some people who believe that As soon as the average temperature goes up just 1 degree, Gunnera will take off right over Ireland, and that we will be beating them back to get in our front door.
Gunnera tinctoria  outside Kildavnet Tower on Achill Island, County Mayo

Here is my (slightly dramatised) depiction of what a global invasion my look like.

On a more serious note,
In New Zealand, where it is also invasive, there have been experiments with several herbicides for a number of years and aerial spraying over large areas has been conducted. The New Zealand Department of Conservation (DoC) have reported their suggestions on the control of Gunnera tinctoria.

Letterfrack area of Co. Galway.

Mayo County Council, the Heritage Council, National Parks and Wildlife Services, the Biodiversity Fund and UCD have jointly funded a project to carry out experiments on the development of measures for the control of G. tinctoria.
Alongside the experiments a mapping project of Achill Island is being conducted. The mapping will provide a baseline for future projects to monitor its spread and the success of control. It will provide an insight into the habitats at risk of invasion, its means of spread and where prevention could be introduced as a means of control.

So hopefully I don’t get any angry emails form anyone for mentioning Gunneras or that I have ruined Sting’s ‘Englishman in New York’ song. Apologies in advance, I am not saying that everyone should run to there garden centres and get themselves a Gunnera plant, or that the global Gunnera invasion will or won’t happen. All I’m saying is good or bad, I think that the Gunnera manicata is a beautiful plant to admire.


  1. Beautiful leaves. Too hot and dry for them to survive here in Central Texas (USA). Not that I am part of the green movement but perhaps the leaves could be harvested, allowed to ferment to make some sort of methane, or energy source. Their terrific leaves seem to relieve us of a great deal of carbon. When you have loads of lemons - try lemonade?

  2. Super cool post..beautiful pictures..gorgeous greens...i love it! I can imagine the face of the greenman full of all that lush foliage...beautiful!

  3. I've got a Gunny in my back yard(that's what we call him, the rest are all Robert as in Robert Plants)! There is a place here on the Island - Tofino - that has huge, huge, huge ones too! Mine isn't doing so well this year although I've been watering it lot's - any suggestions? I liked your Gunnera world too!

  4. Hello,
    Very nice post and I love the pictures with the global invasion.

  5. Hi, thanks for visiting my blog- really enjoyed this post (also the piano one)- I totally agree that they are so beautiful they should be cultivated, regardless of whether some species are invasive or poisonous. On this point, I do remember when I was a small child getting some blisters on my arms after playing among a jungle of them in my grandparent's garden- the scars lasted some years! but so what, it didn't kill me, and the excitement of being surrounded by them made it worth it!
    I await the invasion...

  6. I don't know if I've ever seen either of these plants before, but I especially like the non-invasive, featured version. Your photos are incredibly lovely, and the name Dinosaur Food is just too apt. They look prehistoric, those plants.

    The biological implications for the symbiotic relationship with the algae are potentially huge. I just really hope that Monsanto doesn't get ahold of any of the early research and create some new nightmare for us.

  7. Oh, and a p.s.: I loved the title! So very clever. :)

  8. That is one cool plant! Love it. Once again, your photoshopped images are hilarious. LOL.

  9. I love the title for this post and I really loved the global takeover "photos". Very funny stuff.

  10. I will have Sting's song in my head all day but that's Ok I love it. Also love the plant. Wish I had room for it myself. You did a great job of the photoshop invasion. Odd it hasn't become a movie, the invasion of the Gunnera, pretty scary, such a huge plant. But I do agree with you about it. And it is beautiful if not more than a bit anti-social with all those thorns.

  11. very good article...we grow a couple down by the river here in south west england but we have to cover them with their leaves and bracken or anything to protect them from the frosts and still they poke their noses out too early and get bitten by the late frosts... magnificent plants and i love them but choose not to hug them!

  12. What a fun post! Love your interpretations of the invasion. I do love the large leaves and the non invasive Gunnera would be great to cover my alien Bishop's weed!

  13. I think the G. manicata beautiful too, and glad to see the distinction drawn between it and. G. tinctoria with such photoshop flair. I can practically hear that G. tinctoria creeping over the western coast of Ireland all the way here in Calif.

  14. Great post and a fine job with the invasion photos. I tried to grow G. manicata here in the Pacific Northwest a few years ago but it just never took off and then a heavy frost finally did it in. Maybe it's just as well!

  15. funny photos!

    I can see how this would be something you either really like or really don't (even without the possible invasiveness factor). I think it's definitley very cool - prehistoric and interesting. But...also something that wouldn't "blend in" so well in my garden!! :)

  16. The photos of the invasive species remind me of kudzu! Left to its own habits, that is exactly what our region's monster vine will do. Your dinosaur food plant is impressive, and I think in the proper setting, as portrayed in the water photo, it is a truly remarkable plant. I see why you like it!

  17. I love Gunneras, wish they were hardy in my part of Canada, they are just gorgeous, especially at the waters edge.

  18. Great post. I also love Gunnera. I have just planted three! I discovered it at Wisley after finding I could stand up to my full height under it!

    Elspeth, Oxford

  19. Great pictures, and lots of things I didn't know about this 'dinosaur' plant. There is one growing right on the edge of a stream in Como Lake park, where my hubby & I like to walk. It's amazing how quickly this plant grows, from a small bump on the ground to five feet tall in weeks. Amd it always looks graceful.

  20. Fascinating!! stem glands. Who knew. And I'm more and more convinced that we're going to have to take ours out of the pond. boo. But thanks for the info!

  21. The plant is beautiful though, needs lots of space. I wonder if it could survive harsh continental winter in Croatia?. Interesting post.