EP14: Why the balsam bashers might be wrong

The transportation of seeds or whole plants is an offence under the Invasive Alien Species (Enforcement and Permitting) Order 2019 in England and Wales and Section 14AA of the Wildlife and Countryside Act in Scotland. This means that no seeds or plants should be removed from the site where they currently grow, and sowing seeds or planting elsewhere either deliberately or accidentally would be a particularly serious offence. – Curtis Wright (phone: 07920 516559. email: curtis.wright@apha.gov.uk)

In this episode I discuss with Pete Yeo from Future Flora why invasive plants may actually be good for the environment. Does the science stack up in favour of balsam bashing?

As Pete says “What reductionist science would call an opportunist or invader, a more holistic worldview might call a Gaian first responder. Put another way, one person’s weed is another’s wisdom.”

There is a transcript of this episode underneath the show notes for those with hearing difficulties.

Show Notes

About Pete Yeo

Himalayan Balsam Bashing

Pete is, amongst other things, a naturalist and plantsman, having been fascinated by plants, especially their patterns and relationships, for over 35 years. Whilst he has studied horticulture and ecology formally, plants themselves have been his most meaningful teachers.

You can visit Pete’s page Future Flora on Facebook for an open conversation about the changing nature of Britain’s wild and cultivated flora, also exploring alternative narratives on the plant realm.


Robin Harford:
Welcome to another episode of the Plants and People Podcast. This is Robin Harford from EatWeeds.co.uk, and I’m here with Pete Yeo, who is the man behind Future Flora. And I first met Pete last year, so a year ago, because I heard that he was doing a talk in North Devon on invasive species, and an alternative model to them; “Are they a friend, or are they a foe, or are they somewhere in between?”

So, recently there was an article in the Telegraph really going on about, “We need to start balsam bashing, and getting rid of this bloody immigrant.” And so, I thought, “Well, Pete; he’s the man to talk to.” His talks are really, really inspiring and good, and he’s got the science, and he’s just got some interesting takes on the whole invasive species discussion. It’s not cut and dry. For years, I’ve always been promoting that, actually, invasive species are here to teach us something; that, if we can learn nature’s ways, being a very young species ourselves, maybe we can learn a thing or two. So, Pete, welcome to the show.

Pete Yeo:
Thank you very much, Robin, and hello everyone.

Robin Harford:
So, just give a little bit of background. You’re a plantsman. How did invasives come into your kind of thinking and why invasives? What grabs them for you?

Pete Yeo:
Well, I won’t give you the whole story, but the last three or four years, I’ve been really kind of indulging my interest and passion for plants and the relationships between plants. And it was some years ago now before, that I kind of realised that, as I was getting to know plants better from a kind of horticultural garden point of view, it was quite clear that some of the plants that we grow in our gardens are actively naturalising across our British landscape. And I was kind of really struck by how that might play out, and with environmental kind of sensibilities as well. I was obviously aware of climate change, and the potential impacts on our flora; of that. Yeah, just started to kind of speculate about how things might pan out, and generally kind of look at immigrant plants; and there’s a whole ‘nother conversation we could have about how we project onto immigrant plants as we do with people.

Robin Harford:

Pete Yeo:
But, when you look at immigrant plants, the kind of stand-out group are the invasive plants. And, the more I kind of looked at them, the more I kind of stumbled upon references to an alternative way of looking at invasive plants, and that they weren’t always bad. And, in fact, even when they were held to be bad, that the evidence for that didn’t really stack up. And certain books, as is often the way, came in front of me, and I kind of hungrily read them, and started to kind of have a very different perception of invasive plants, and perhaps of invasive species more generally. And it’s that that I’ve been starting to look at more closely the last few years. And have quite a different perspective than many people, and particularly classic conservationists, for example. Yeah.

Robin Harford:
Yeah. Okay. So, the particular immigrant that I wanted to … The reason I called you up and said, “Look, come on, chum. Let’s get you down on record.” Is really to discuss Himalayan balsam. I know, obviously, there’s Japanese knotweed, there’s rhododendrons, tonnes of other so-called invasive species. But, it’s Himalayan balsam bashing season at the moment.

Pete Yeo:
Mm-hmm (affirmative).

Robin Harford:
So, what’s your take on the usual argument that Himalayan balsam, it comes in, it crowds out our native species, it’s a thug, it just disrupts our waterways, and is unsightly, stinks, and we should be doing everything in our power to be basically committing genocide against it? Not to be too emotional.

Pete Yeo:
Of course not. I mean, obviously, I’m familiar with the plant and where it grows, how it grows. It’s a very pretty plant, generally. I mean, that’s why I think it was introduced to this country in the first place. I mean, I’ve got my own views on the plant and its behaviour. But, there’s a couple of books in particular that I’ve been quite influenced by. They’ve resonated very strongly with me, what they’ve had to say about Himalayan balsam. One is “Where Do Camels Belong?” by British author Ken Thompson, and “The New Wild” by Fred Pearce, another British author.

Robin Harford:
Yeah. Fantastic books.

Pete Yeo:
Both wonderful books openly questioning and challenging the standard view on invasive species, both flora and fauna. And both of them clearly point out that much of the evidence that should be there to support the impacts of Himalayan balsam on biodiversity … Because it’s an annual, it dies away at the end of the growing season, and then leaves the soil bare, which is then open to winter rains, and the high river volumes for erosion, and things like that, and the river banks get eroded. The negative effects on pollinators, and so forth. A lot of the research just doesn’t stack up.

And, even if you go on to the CABI.org, which is a centre … If I can remember it properly. A Centre for Agricultural Biosciences International. Basically, it’s a kind of national body, in this country, to look into … Well, a big part of what they do is looking at invasive species and from an anti-point of view. But, even on their website, when you look at their data sheet on Himalayan balsam, they’re quite honest in saying that a lot of these … I can’t think of the word. Accusations aimed at Himalayan balsam, even they say the science is very, very fuzzy. There’s not really any good evidence to support the biodiversity impacts, and so on. And we can kind of drill that into it.

Just from my own point of view, the accusation in terms of once the annual plant has died back at the end of the growing season, it’s leaving the riverbanks open to winter erosion from high river volumes because the plant has smothered out everything else, and there’s nothing there stabilising the bank. That just doesn’t feel right, to me.

You know, I could be wrong. I mean, I haven’t actually gone out into the field on my hands and knees and really kind of explored this. But, it just doesn’t feel right. I mean, you taken some annual bedding that you’ve had in pots or containers the following spring, after they died back the autumn before; my experience is that those clods of soil are very, very firm, and the root balls are still very much intact, even though the actual plant has died.

And, of course, there’s plenty of other perennial species that are growing along with balsam, as Thompson and Pearce point out. The native species that Himalayan balsam is supposed to be out-competing, or competing with, are common ruderal species … So, that’s species that grow in disturbed, in this instance, typically moist habitats like stinging nettle, bindweed, docks, cleavers, and the like. They’re quite bold plants in their own right, but they can kind of cope with that competition, to an extent. So, it’s not as if they’ve been completely rubbed out of the area; they’ll still be there.

And there’s evidence to suggest, as Ken Thompson lists, that, whilst Himalayan balsam is competing, if you can accept that perception of how plants interrelate with each other; they’re competing with common ruderal species, natives, but actively suppress other non-natives. So, when you remove Himalayan balsam where it’s invaded, a lot of other non-natives come in, and it’s just hamster wheel time, as it so often is in these scenarios.

Robin Harford:
Well, let’s say who they are. The conservationists. They’re the old guard, archaic, dinosaur conservationists who, unfortunately, control the whole of this bloody country and all the regulations. Now, I know you’re far more gentle than I am there. But, you know, it’s time to call them on it, because they haven’t got the science. Whereas, if you look at Pearce and the other chap, they have the science. It’s listed there. And I’d just like to point out that Fred Pearce was massively was massively anti-invasives, until the data started questioning his model. Yeah? And now he has come out with his new book, “The New World”, on the side of invasives.

So, for those conservationists who are twitching and wetting their knickers at this point, I really do strongly suggest that you go and check out his book, and check out the science, and stop giving immigrants, as we do with human immigrants, a bad rap, just because they are other, and you personally don’t understand them.

Pete Yeo:
Yeah. I commend everyone to read “The New Wild”, it’s a wonderful book, and there is plenty of evidence that the science in favour of the anti position doesn’t hold water very much, if at all, and there’s evidence to suggest the opposite … In terms of the negative pollinator effect with Himalayan balsam, there is evidence to suggest the opposite, that there is what they call an adjacent benefit, so that other native riparian riverside species that are flowering at the same time receive more visits rather than less when they’re kind of in the same area as Himalayan balsam, Himalayan being super popular with honeybees and other pollinator insects, which is a common trait of many … Well, invasive plants generally, they tend to have very broad bandwidth appeal to pollinators. Which is not really a surprise, when you consider the kind of circumstances they tend to be arriving in where there’s vegetation has been, to varying extents, removed from an area. So, the local pollinators and other insects have a lot less to forage from.

Robin Harford:
And who’s been doing that removing?

Pete Yeo:
Quite often, good old human beings.

Robin Harford:

Pete Yeo:
Of course. And, as Thompson says, so often we kill the messenger. We get the plants, an or animals, whether you call them invasive or not, or pioneer opportunist species, that kind of come in and thrive, or perhaps are a response to disturbance. You know, you get the plants and animals that we deserve, the same way as we get the governments we deserve, God bless them. And, yeah. It seems to be a lot of evidence support this alternative, much more kind of positive, outlook on invasives. I mean, it’s quite a broad topic.

The way I am now starting to look at invasive plants is to try and get a much bigger picture, and I’ll bring this back to Himalayan balsam in a second. The bigger picture view of what they might be doing, what their ecological role might be. And I’ve been very influenced by an American author called Stephen Buhner, who’s written about plant intelligence, generally, and invasive plants; particularly Japanese knotweed, which he works with over in America as a herbalist, amongst other things. But, he makes the point that every living being, every living thing that’s expressed into physical form, has an ecological function.

The challenge to anyone who wants to have a kind of say in the matter is to find out what that function is. And there’s another American author and permaculturist called Tao Orion, who’s written another wonderful book called “Beyond the War on Invasive Species”, and she takes that further. It’s like, yeah, you need to find out what that plant is doing. It will have a role in the ecosystem, in the habitat. What is it? Take the time, and even if you come around to the fact that you still don’t want it, you want to kind of stand behind cosmic will expressed through you versus cosmic will expressed through the larger system, and you still want to go head-to-head with that; then, try to do it in a way that’s following the grain of nature rather than butting against it with chemicals, et cetera.

So, back to balsam … And I’m kind of skipping around a little bit. But, there’s a project in Germany. A place called Weisbaden, which … And as many people will know, many of the parts of Himalayan balsam are edible; the young shoots, the seed pods, the flowers.

Robin Harford:
Possibly. Yeah, okay.

Pete Yeo:
As I understand it.

Okay. So, in respective, there’s edible parts of the plants, but there’s this project that are making food products-from the plant in order to finance the eradication of the plant.

Robin Harford:
Peter Becker, yeah.

Pete Yeo:
Yeah. Which, is kind of amusing, really. And, interestingly, the Himalayan balsam … And I was kind of surprised to find this out, but it’s a Bach flower remedy, but also one of the five ingredients of the Bach’s Rescue Remedy. And its key word associated with it is “impatience”. Which, you can feel the impatience of a lot of people, and conservationists, particularly, with the plant. And so, you kind of wonder what might be going on at a deeper level.

But, just going back to how I look at invasives now, and looking at the ecological function … Though, I take it a little bit further, and imagine, if you like, that the planet, Mother Earth, Gaia, however you want to describe it, has the equivalent of green skin. So, in the same way that when we graze, cut, or otherwise damage our skin, there is an immune response that is engaged to heal that. And, the more I consider, it seems quite plausible that invasive plants are that immune response of that kind of macro green skin vegetal system. That are drawn in to an area, depending on the degree of disturbance, and the more powerful kind of invasive plants tend to correspond with the greater waste that an area’s suffered.

Robin Harford:
I think Pearce mentions that, doesn’t he?

He mentions about how they tend to hang out where humans have basically messed up their local ecosystem and land base.

And so, the whole concept of balsam bashing, and pointing the finger at the invasive, forgetting that there’s three fingers pointing back at ourselves; it’s not really dealing with the causes. For me, I mean, that thing where Buhner says, “Everything has an ecological function,” for years, I’ve taught that plants have … If we’re patient enough, and get out of our human arrogance thinking we know it all, and actually observe, like the ancient Taoists did 3,000 years ago in China, there are … Nature tells us something. Nature is always giving us guidance, that’s why she is seen as a teacher. And that the invaders, so called, are, like you say, like Pearce says, like loads of other people are beginning to come to a realisation.

We’ve got to be looking at our habitat loss. We’ve got to be looking at our industrial agricultural practises. You know, if you don’t want the Himalayan balsam here, or the Japanese knotweed here, ask yourself, “What is the human doing that is causing this,” like you say, “This healing to take place?” Because, finally, in the last two years there’s all these books with the science referenced in the back of them, pointing to the fact that, actually, the human is the cause of this. And we are the problem. They’re not the problem. They’re trying to fix the problem.

But, one of the reasons I really was inspired, and loved your talk last year was … Because I’ve always had this thing like these invasives, whether it’s a plant, or it’s something like Muntjac; they’re second guessing climate change. And one of the things that you brought out last year was that, a lot of these so called invasive species come from climates that the climate of the British Isles is expected to be similar within the next 20 years. Is that correct?

Pete Yeo:
In certain instances, yes. I mean, some of the invasive species that are actively naturalising in the landscape now, holm oak, for example, the evergreen oak; they’re kind of, perhaps, placing our wooded landscape, putting it in a more resilient stance. But, I think with Himalayan balsam, I haven’t noted with that one … I think it’s the case that the … And I can’t remember the timings of introduction off the top of my head. But, I think it’s probably the case that the climate here was already quite conducive.

Robin Harford:
It was 1830’s I think it came in. It was brought in.

Pete Yeo:
And, what you’d have to kind of look at then, is when was it first recorded in the wild? And, amazingly, they have this information for many of these plants. And there are these standard lag periods between introduction and a plant, if it’s going to kind of become naturalised, or even so called invasive; there were these lag periods. It’s 170 years for trees, about 130 years for shrubs, and decades or less with herbaceous plants or annuals like Himalayan balsam. So, what you need to look at is, “Okay. When was it first introduced? When was it first recorded in the wild?” If it was just a period of decades, then it could be that the climate was already conducive.

If, like bay laurel, for example, which was introduced, perhaps, by the Romans … And then, you add on 130, 150 years. And then, okay, when was it first recorded wild? 1924.

Robin Harford:
Oh, right. Wow.

Pete Yeo:
Way beyond the lag period.

Now, to my mind, my inexperienced, non-scientific mind, maybe that’s a good thing. That strongly suggests that climate change is at play. The climate is sufficiently warm and compatible with what bay laurel is used to, particularly in terms of seed regeneration, that it’s like, “This is okay for me now. I’m liking this,” because of the warming that’s come since the Industrial Revolution.

Robin Harford:
Mm-hmm (affirmative).

Pete Yeo:
Because of that huge period between introduction and running wild. Off the top of my head, I can’t remember the kind of details for Himalayan balsam, but what we do know … And this is kind of cutting back to what its ecological function might be … Is that it’s one of these plants, like ivy and like cherry laurel … Ivy is regarded as a native … Which, that language has become increasingly uncomfortable for me.

Kind of meaningless. And cherry laurel is an introduced, and regarded as an invasive. But, they all, Himalayan balsam as well, are known to thrive on high levels of CO2. I’m guessing we’re likely to see more of those kinds of plant, or those kinds of plants proliferating, become more successful, because there’s more CO2 in the air.

Now, from a holistic macro system point of view, is that response kind of inevitable? Is it a part of the rebalancing process that would need to be underway? That Gaia will try and kind of redress the imbalance that we’ve wrought? But, what else might Himalayan balsam be doing? We know it thrives on high nutrient load. It seems to have a very high mineral content, which suggests it could be one of these plants. And this is where more research needs to be done with a neutral mindset at least, rather than kind of set up to look for problems, like if you’re funded by a body that wants to kind of prove that, perhaps.

But, could it be that Himalayan balsam is the kind of plant that acts as a moderator, kind of a plant sink for surplus carbon in the atmosphere, or surplus minerals, perhaps nitrogen in the soil. And, of course, where you see it is in river systems, alongside rivers. And, more often than not, there’s going to be relatively intensive agriculture, perhaps with surplus nitrogen runoff. Is it playing some kind of role in that whole game?

Now, from a holistic point of view, you’d think, “Okay. Well, let’s assume it is. We’d need those minerals, that surplus of whatever it is to either be locked down as carbon, or as minerals, to be put back on the land, and maybe upstream again, if the system’s purpose is to kind of hold the vitality of the soil. So, how might that work?” And this is all pure speculation.

Robin Harford:
Sure. Of course. But, the questions need asking.

Pete Yeo:
And might be completely baloney, but we can be honest about that.

But, given that livestock tend to love eating Himalayan balsam, that represents a possible return path for those minerals. Because, they’re going to take it further up field, perhaps further up the valley, and drop it back on the fields, or whatever. I don’t know. But, it’s an interesting thing. And is anyone looking at that? I don’t know.

Robin Harford:
Right. Yeah. Well, if anyone’s listening to this who is looking at exactly that … I mean, Pete is completely up front. This is purely speculation. I say all my courses, I don’t do woo-woo. But, I have to say, at this point, the questions that I think are fascinating, that there possibly is some semblance of a clearer perception of how invasives are functioning within our ecosystems that currently we’re not entertaining.

So, I really like the idea that … I spoke to a chap who use to cull Muntjac, and deer in general for the lords and ladies in Scotland. And I asked him, I said, “Muntjac is an invasive species,” and, “What’s your take? You’re someone very close to the land, you’re embedded with the landscape, you’re observing and paying attention to the shifts and moves of this progression and impact that climate change is having. What do you say?” And he came and said, “Second guessing climate change.” I mean, it was just straight off his head. And I do think that when you were talking that … And I’ve heard it from two other people, so this is three people completely unconnected all coming to a similar consensus about how the ecosystem is shifting.

Old guard conservationists are fortress conservationists. Humans should be removed from the landscape, blah, blah, blah. We see this all over the world, and it’s causing chaos. What the balsam bashing community don’t seem to be getting is that we are moving, and climate change is happening, whether you like it or not. The evidence is absolutely there. And people close to that … And especially plant people see it happening in development through the years. And it’s a question of, “When are you going to wake up and realise that the Earth, Gaia, is trying to tell the dumb ass humans something and we need to be paying attention?”

Pete Yeo:
I mean, whilst I’ve studied horticulture and ecology formally, I’ve kind of … Most of what I’ve learned of value has been from plants themselves. As you do, and other people we know … Just getting out and direct experiential activity with the plants, and within context. Context is one of the most important things I’ve ever learned. And part of context is that it’s always changing.

And back to the ideas that are still prevalent within the conservation fields of … There’s equivalent with the political landscape at the moment wanting to make America or Britain great again, getting back to the good old days.

You can sympathise with that to an extent because of so many things that are happening in the world, but, of course, you’ve got to keep moving forward. I mean, climate change, no matter how effective we might be at reducing our carbon output in the next five, 10, 15 years, or whatever; there’s an awful lot of carbon coming through the system yet. So, we’re kind of locked in to a degree of climate change. Slowly, more and more people are starting to kind of realise that they’re having to … We’re going to have to embrace at least some of the introduced plants that are actively naturalising, some say invasively so, in this country because … And Fred Pearce points this out very effectively. We might be really, really glad of those plants. Particularly, if we get accelerated climate change to the extent that some of our key, anchor native species literally can’t keep up.

For years now, I’ve been saying we’re a nation of gardeners, great. I mean, maybe that in itself … We’ve got one of the most smallest native floras in the world, and yet, one of the largest cultivated floras in the world, with the Edwardians, Victorians, and Georgians bringing in plants from all over the world, from our empire. And we’ve grown them in our gardens. Many have leapt the fence. Although, Williamson’s law … Which you may know about, and some of your listeners may know about. For every 100 plants that are introduced, 10% go on to naturalise in our landscape. 10% of those become invasive. You’re talking about 1% that become invasive. And, if you listen to someone like Ken Thompson, he’ll say there’s evidence suggesting that, even with those species, between a period of 50 to 200 years … Which, bear in mind, is beyond the typical human timeframe, which is why we’re missing it.

Even those species blend into the background. I mean, its native range … Himalayan balsam is not invasive. Japanese knotweed is a pioneer on lava. It’s one of the first plants, if not the first plant, that can get onto volcanic lava and start the process of turning it into soil and hastening the arrival of forest.

So, rather than the old kind of way of looking at ecological succession as kind of the initial pioneer plants coming in and then, progressively, they’re out-competed by wave after wave of more suited, fit plants, until you’ve got forest or woodland back in that location; the pioneer plants, like knotweed and Himalayan balsam, are kind of preparing the way for those aspects of themself as one macro vegetal system that can come, arrive, and fully manifest all that vegetation can be in that location. And that’s not to kind of discount humans. We know humans are having … They’re very much a part of nature, and we can work with nature rather than against it, but we have to be cognizant of those larger processes that are happening. Pristine wilderness, along with many of these terms like “native” and “invasive”, they’re becoming kind of mythical, and myths that perhaps aren’t serving us anymore.

Robin Harford:
We were talking just earlier, weren’t we, about “re-wilding”, the word “re-wilding”, and that I’ve always felt quite uncomfortable with it. I mean, I understand that people who talk about it, where they’re coming from, but re-wilding is almost this romantic vision of going backwards to this time of pristine environments; of how it should be, without humans. Well, the term “future wilding” would be far more appropriate, for me, because that is taking in all these models that we’ve been discussing.

Pete Yeo:
Yeah. You’re making me feel good about the use of “future flora” for my Facebook page now, bless you. But, no. I mean, I was quite excited by this idea of re-wilding. I mean, on so many levels, it feels like a really good idea. But, I happened to drop an organisation who are involved with this … A new organisation, I believe. They’ll remain nameless for the sake of this interview.

To be nice about it. But, I was quite shocked, actually, by the response I had. I kind of sent them a wee note saying, “Just out of interest, what’s your position re: so called invasive species? Are you accounting for the use of some of the naturalised, and perhaps in certain instances, invasive species within your kind of re-wilding programme; particularly with a future proofing perspective, with climate change and all the rest of it.” And they kind of knocked that one back to me.

Robin Harford:
That was really surprising, actually.

Pete Yeo:
They said, “We’re a conservation organisation, and,” ..

Robin Harford:
No, you’re not.

Pete Yeo:
And they really are, by the sound of it. In the sense of, they’re conserving what there is.

Robin Harford:
Wilderness as museum.

Pete Yeo:
Yeah. And it’s like, you don’t need to consider that for very long to see the flaws. To my mind.

Let alone what my heart feels about it. But, it doesn’t make sense. We’ve got a host now of introduced species that are out about in the landscape. And I was just reading, actually, there’s a new report out by the RHS, the Royal Horticultural Society, looking at the implications of climate change on horticulture, gardening, and gardeners. And it’s a very interesting read, love the science on climates in there. And they’re quite even-handed. I mean, there’s a lot of standard jargon and narrative around invasives being bad and negative, and invasive species, flora and fauna, held to be one of the key threats with climate change … As is becoming obvious in this interview, neither of us necessarily buy into that narrative.

But, they were talking about holm oak, for example, Quercus ilex, which we mentioned a bit earlier. And they were actually acknowledging that that actually could be a beneficial species, in terms of our flora in this country, as a new … I mean, if you look at the bigger picture, it’s just a different form of oak, ultimately. I mean, we call things, “This is a species of oak. This is another species of oak. This is a species of thistle. This is another species of thistle,” whatever it may be. If you zoom out, it’s just one continuous flow of DNA.

So, the holm oak … Even the turkey oak as well, which is a deciduous oak, but from more southernly regions that is also actively naturalising in this country. They’re more suitable, resilient forms of oak for the climate that is coming to our landscape soon.

In geological timeframe. And it just seems sensible to kind of go with that. And, interestingly, there was an article in a little kind of freebie-type newspaper put out by Common Ground and the Woodland Trust recently, and there was an article in there, I think it was two ecologists and an environmental campaigner, speaking up for the likes of sycamore and holm oak, turkey oak, horse chestnut, and trees like that, and saying, “We should accommodate these species more in our planting, in our tree planting across the landscape. We need to give them a chance, because they’re going to serve us well.”

So, slowly people are starting to think ahead. And the Forestry Commission have been talking about this for some time as well. It’s official policy that people who are planting woodlands, whatever, they need to plant between provenance of particular species, between two and five degrees south … Two degrees is Brittany, five degrees is kind of over the Pyrenees area. So, that’s growing seed from native species, let’s say. But, seed that’s come from a field maple, or an oak, or whatever from the south of France, because it will be that little bit more suited to the warmer temperatures that are coming our way. And, again, that makes sense.

But, even the Forestry Commission have been making comments in the direction of, “We need to be a little bit more creative, and imaginative, and use a larger palette of tree species in our woodlands in this country.” And that’s just woodlands. So, there’s many angles we could take that conversation, I know.

Robin Harford:
There is. I mean, the whole invasive species discussion slash debate is obviously going to be hotting up as climate change develops; definitely a pun intended there. And we just have to watch this space, and see what science is coming out, and just hope that conservation organisations actually start putting the evidence on the table. Because, at the moment, my feelings about many of them is that it’s a bit like the old witch trials, the Inquisition. “We’re going to burn someone on a feeling,” you know? “Well, where’s the evidence they’re a witch?” “No, no, no. I just know they are.” And I think it’s time that we really get the evidence out and down, however that can happen. Because we all know that scientific research has vested interest that pay for it to push certain agendas. But, there are these kind of outsiders and iconoclasts who are putting their neck on the line; like Fred Pearce. Complete about turn. Which, fair play to the man, that’s pretty ballsy when you’ve got a reputation that is potentially going to be wrecked by doing so.

So, this is what Richard Mabey had to say about Himalayan, or as he calls it, “Indian” balsam back in 2011. He says, “I’d like to raise a personal cautionary note about the balsam bashing group’s activities. We very often forget that Indian balsam grows best on bare soil, where other plants aren’t growing at all. I’ve been watching the plant for most of my life, certainly the best part of 40 years, and I can’t say I have ever seen an instance where it has displaced native vegetation. And I wish, because it would greatly strengthen their case, if balsam bashers had some hard science about what happens to a patch of native riverside vegetation when Himalayan balsam moves in.

As for the future, I think we have to accept that Himalayan balsam is here to stay. The more that machinery churns out the area around ditches, the more the muddy corners of fields are disturbed. The more we dump the dredgings from rivers onto riverside banks, the more we actually create the open, muddy situations that the fruits of Himalayan balsam just adore. And, maybe, we should also remember that cautionary note from poet Anne Stevenson, “Plant extinctions are happening all over the globe as a result of climate change, pollution, habitat loss.” I think we really need to think seriously before we choose to eliminate newcomers to the ecosystems of any country, however aggressive and invasive they might be. In 50 years time, they might be just what we need.”

So, thank you, Pete, for the discussion.

Pete Yeo:
Yeah. It’s just that, I mean, I fully concur with what Richard was saying there. In my experience, speaking with ordinary people when I do my walks, and talks, and presentations; when they hear what I have to say, this information around a completely alternative narrative on immigrant, invasive, whatever descriptor you want to use, plants, the overwhelming response is a kind of like, “Yeah, no. That actually kind of makes sense.” And that’s really interesting. The very least why I do what I do, is to kind of just balance up the debate.

Because it’s been imbalanced for so long.

And the imbalanced side, the more I look at it, just does not stack up. It doesn’t make sense. And so, I feel we need to kind of just openly, honestly look at this other side. Like you say, it may be that there is good, hard evidence for some of these species, perhaps. Again, that may be only a short-term effect.

But, let’s have an open, full debate on this. And I think we’ll all be the richer for that.

Robin Harford:
Thank you very much.


  1. I don’t disagree in principle, but it’s not just about the plants themselves, it’s the whole ecosystem and how each part interacts with another. Invasive plants can monopolise / euthanize otherwise very diverse habitats which support a wide range of species, and it’s often a delicate balance for them. Don’t forget, the objective of plants like knotweed is global domination! (Makes good jam though :)).

    • Hi Carly 馃檪 I hadn’t heard of Knotweed jam before. And I agree, it’s about the whole system. Yet trying to hold all of those possibilities in my head makes it hurt, so I focus on the plants. To be honest, the ‘global domination’ assertion I have difficulty with these days. If highly ‘competitive’ plants had had their way historically the planet would look very different (less biodiverse) I think. Where there are biodiversity impacts from so-called ‘invasives’ (and evidence is sparser than we are led to believe) the effects seem to be finite, whilst still significant to the human timeframe. Yet not Gaia’s perhaps. Japanese knotweed initiates the regeneration of forest on volcanic extrusions. This process takes many hundreds of years, with knotweed forming a monoculture for about 50 years at the initial stage (it’s one of the few things that can grow on cooled lava, with all the heavy metals etc). In our landscape it’s known to be drawn to polluted soils/habitats and one wonders whether, once it’s achieved its ‘mission’ to clean those soils, it would recede in dominance – as other ‘invasives’ now appear to do (like Garlic mustard in the U.S.). One thing’s for sure, it’s a fascinating plant/aspect of Gaia. Warmest, P

    • Of course, plants don’t have an abstract ‘objective’, such as ‘world domination’! Nor do they engage euthanasia, aka mercy killing, obviously. 馃檪 Both of these are very human concepts, and it is a tremendous stretch to impose those concepts onto other species, especially plants.

      As discussed in this podcast, each plant has the ability to thrive in a particular ecological niche. If those conditions exist, the plants suited to those conditions will thrive. Japanese knotweed is apparently a pioneer species, adapted to thrive in the hostile conditions of cooled lava, where little – if any – other plant life can survive. Perhaps we should consider what combination of compaction, heavy metal contamination, and other soil conditions are present that allows this plant to thrive.

      Aside from jam, the young shoots and tips are edible as a vegetable. Harvest seems a much more sane control method than splashing about yet more poisons – which are more damaging to our ecosystems than any plant.

  2. Great read thanks! I love the fact that someone is actually looking at the plant in a “what role does it play in relationship to us” sort of way. I have been following the growth cycle of Himalayan Balsam the past few years and we have tons along the river banks to enable me to do so. There are lots of natives like the cleavers, mustards etc. that grow happily along side it and I always felt that there must be something more to it than a horrid invader, not being very horticulturally minded I didn’t really know much.
    I am a Flower Essence practitioner and have studies the cycle of certain plants and where/when they show up and how that relates to the human emotional cycle predominant at the time. The last few years with all the hypersensitivity and judgemental aspect of us humans throughout all the political rot that has caused so much hassle it was interesting to note that new little Beech trees were showing up everywhere, Beech being the main Flower Essence for those who tend to be too judgemental of self or others and can be overly sensitive and take everything to heart ( like most were doing with the political debating side of things)
    Himalayan Balsam is a really interesting one! As you mentioned it is the Bach Flower remedy “Impatiens” and deals with the quick, intense irritable type emotions that we can experience. Following the plants cycle of Rapid growth and the traces of red on the stems etc you can relate that to how the “stressor” irritates and grows quickly, the plant then blooms, very pretty flowers often twins that seem to be in a state of harmony, however the smell ( that musty rather off putting smell if you get too close) gives the hint when related back to the human condition that although we may appear less tense there is still something not quite right with us, hints of red on the stems etc indicate irritation is still internalised, simmering within until the seed pods burst spectacularly with a huge burst of energy that if you feel it makes you jump, a bit like us simmering with the irritation and impatience having not dealt with it and we finally blow and the angry outburst can leave those around us quite shocked. Then like the seed pod relaxes and the plant goes into die back to nothing, we go back to our calm self.
    I love just noting what plants are in abundance at any given time and more often than not it relates to the collective state of mind at that time.
    I love how you see the connection on how we treat non native plants and non native people. Its also a strong trait of inviting in what we think we want and then getting all uppity when it doesn’t conform in the way we want it to?
    Ramble over 馃檪
    I look forward to hearing more on this topic and will go have a look at the books you suggested and see what light that throws up for me ….

  3. First of all I would like to say I really enjoyed your talk on absinthe.Ive tasted it and thought it was yummy..got to say though I was so cautious hahaha…all the stories you hear about it! so thank you for clearing up all the myths.
    Secondly on the subject of the `Chinese knot weed’…perhaps it was brought over because of the health and medicinal properties.I came across it in Cornwall. There was a warning about cutting it down and needing to report it to the local authorities because ,if one leaf is dropped it tends to take root.
    Look forward to further to your interesting subject matter.From a new forager 馃檪

  4. The largest cause of native flora extinction/decline is said to be introduced species. That’s what serious botanists have found. Global warming includes the completely natural interglacial 120 thousand years ago when it was a LOT hotter than today and the artic ocean ice-free in summer but polar bears and alpine flowers thrived. Why are polar bears not doing brilliantly today? Because of reduced land area with things they need like seals and peaceful coastal land without industrial development and with quiet snow banks in winter.

    Same goes for our rare plants, often species found in rare habitats like high mountains or clean river banks. When the balsam takes over dozens of square metres (and incidentally I’ve never seen it eaten by anything including the cows occupying the riverside meadows near my home with massive spread of balsam) we lose uncommon plants that used to grow there. I grow rare alpine plants in my garden and they love the summer heat, don’t seem to mind warm winters but succumb to the usual garden weeds variously Roman- [goutweed, large dandelion species] and cultivated spreaders. Proper botanists say that the biggest threat to rare plants is not the climate but introduced species, and that seems very reasonable.

    • Hi Frances

      “Proper botanists say that the biggest threat to rare plants is not the climate but introduced species, and that seems very reasonable.”

      This might be true right now, but in 30 or 40 years as climate change really gets a grip?

      There is no point in trying to conserve the Holocene ecosystem, anywhere. It is doomed. The whole thing is doomed, probably as doomed as the dinosaurs were 65mya. The whole global climate is going to change, the range of everything is going to change due to climate change, and the whole invasive plant and hybridisation situation is just going to throw the dice a bit more.

      I don’t want this to be seen as “defeatist” or “depressing”. It is just the way things are. We aren’t going to stop climate change, and that means this is the Anthropocene. All change here.


    • Frances, hi. Thanks for your Comment 馃檪 You illustrate the ‘right plant, right place’ (or vice versa) aspect of horticulture, and indeed ecology, very well. Many plants are suited to fairly specific situations (tho’ there are of course generalists, and good reasons for that). Alpine plants have adapted to the extremes of montane areas, which is why they can’t cope with (being underneath) lowland flora. Nature designs for her needs, very well. And those situations and needs are constantly changing, for many reasons and over varying timescales. So, rare species and habitats may be on the rise, or on the wane (it’s often difficult for humans to grasp the timescales at play and the direction of movement). And hence plants are always introducing themselves to new areas, by whatever vector (humans being a part of Nature of course), and they always will. So to broadly charge introduced plants as a threat to ‘native’ flora (a term that is merely a snapshot in geological time anyhow – Rhododendron was present in the British isles during the last interglacial) doesn’t do justice to the bigger picture. Nature knows best – this I believe to be true – and so I would urge people to look more deeply at the processes at play and honestly question/explore the role of ‘new’ plants within the larger context – the interdependent, living fabric of our planet. … As a final note, sources suggest at least 90% of local species typically remain following an ‘invasion’ event, and that the few local extinctions would often have happened for other reasons anyway (read Fred Pearce, The New Wild, if you can). As ever, it comes down to the lens(es) through which you wish to view the world. Warmest, P

    • Hello Francis,

      Given the amount of the Earth’s surface now covered by buildings, roadways, car parks, and the like, plus open pit mines… contamination of soil, air, and water by industrial activity of all sorts… clear cutting for timber, palm oil, rubber, and other types of tree plantations, etc, I find it difficult to believe that PLANTS are the number one reason for the decline or extinction of flora native to any area.

      What about the effects of industrial farming: the destruction of complex soil – numbering in the billions per tablespoon in most healthy soils – life by tillage, compaction, erosion, ‘mining’ of soil nutrients, the effects of herbicides, insecticides, fungicides… All to grow mostly non-native plants, too, like maize and soya.

      This whole debate reminds me of the situation regarding the classification of small ungulates in the Himalayas. Scientists could not decide if some of them were sheep or goats. To anyone who had actually spend time among those animals, there was no question! To the scientists who had no direct experience of sheep or goats before traveling to that region, they had to wait for DNA sequencing to become available to differentiate between the two.

      My concern is that our learned scientists may be in a similar position relative to their practical grasp of how plant communities really function, if most of what they know was what someone else told them in a lecture hall, or in a book.

    • Francis – Regarding whether cows will eat this ‘invading’ balsm, I have no direct experience, as this plant, so far as I know, is not found in my locale. However, I am aware that cattle, like most animals, are creatures of habit, and often need to learn to eat plants they are unfamiliar with. If this plant was in our pastures, after making sure it had no toxic effects when eaten by livestock, I would cut some and place it in the troughs from which our livestock are accustomed to eating supplements. (We feed no grain to our herbivores, but they are offered dried seaweed, dried garlic, and occasionally lucerne or sugar beet pellets.) They will almost always begin to explore new plants offered in the troughs as a food, and then begin eating them in the fields. If not, spraying the unfamiliar plant with diluted molasses encourages the livestock to try the new food.

      We assume that animals, like cattle, know what to eat purely by instinct. While instincts are important, cattle learn what to eat by grazing alongside their dams. Cattle and other livestock, managed in a manner that mimics the natural relationship of their undomesticated ancestors with their environment will also be much less ‘picky’ about what they eat. This means bunching up our herds of domestic livestock using portable electric fencing (dogs and herders work as well, but are now considered too expensive), and moving them at least once every day. When moved to a fresh area of pasture, they don’t simply eat the equivalent of ‘bicuits and ice cream’. The grazed portions of the pasture are then allowed to recover before they animals are returned to that area, creating more and more fertile soils, which produce more volume and diversity of plant life over time.

      Isn’t the natural world wonderful?!

  5. I certainly am looking at things differently. The argument of native / invasive and immigrant .. Down with that sort of thing seems more monty Python than pragmatic or philosophical enquiry. I shall look more and ask what need is being met by this plant.

  6. A misunderstanding of Darwin seems to be behind a lot of the thought on things like so-called ‘invasive’ plants, and a lot of other destructive behavior since his famous ‘On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life’ was published in the mid 19th century.

    Distilled to the notion of ‘survival of the fittest’, along with the idea of struggle, the Western reductionist scientific view of the living world is one of unrelenting competition. While competition is certainly one aspect of interactions between various forms of life – co-operation and synergistic relationships are becoming understood to be much more important.

    It is difficult to see these mutually beneficial interactions when we look at the world through the lens of competition and struggle. For example, livestock and even wild animals have been demonized as being destructive to plant communities. Does this really make sense? If we look at the remnants of the few relatively intact ecosystems around the world, along with historical records, reveals that animals are an integral part of all of them. Grasses, for instance, benefit from the periodic pruning of grazing, as well as hoof action, saliva, manuring and the urine can be an important source of moisture in dry regions and season. The mature leaves of the grasses would otherwise block light from the crowns, and oxidize many of the nutrients they contain into the atmosphere, instead of being trampled to the ground where the soil life can use them for food and habitat, or being ‘recycled’ through the grazing animals. The plants and the animals both benefit – which makes sense, when we consider that these organisms evolved together.

    There are countless other examples of the beneficial interactions between species – which fan out, as it were, in all directions – from the billions of micrscopic and macroscopic life forms in every handful of healthy soil, to the fungi that live in symbiosis with nearly all plants, to the insects, birds, hebivores, carnivores, and omnivores. Every living thing within an ecosystem is affected by and has an effect upon every other living thing within that ecosystem, and most of these effects are co-operative and/or synergistic.

    Truly, that ecosystem likely spans the entire biosphere of the planet. Before declaring a ‘war on invasive plants’, we should step back and try to gain a larger understanding of what is actually happening, and what role we humans are playing.

    The use of toxic chemicals to ‘protect’ native flora and ecosystems is ludicrous. And unconscionable.

  7. I studied Plant Spirit Medicine with Eliot Cowan, and one of my classmates did a plant study of Japanese Knotweed – what it told her was that one of the things it can do is alleviate the effects of electro-smog, wi-fi pollution…I trust nature implicitly, and believe that the plants do what they need to do for the benefit of all life here on earth, so I also don’t like this aggressive term “invasive species”; I believe they are doing their work as expressions of the greater planet consciousness.

  8. Native American Wisdom Teachings say that what you need grows around you. Thank you for your comments Tannee and Sally Arthurs. They help emphasise this point and thank you Robin for this great, forward-thinking interview.

    Is it possible that nature could possibly know what she’s doing? ha, ha, ha. Apart from our many eco-sins, we are compulsive meddlers in the natural order of things. We sabotage nature’s efforts to assist us on every level. If we weren’t here (I’m not advocating that scenario) nature would find her own balance without our input. Plants of many descriptions would crack the concrete and break up the tarmac in time. Nature has her way, and who are we to interfere? For all of our good intentions, we’ve ended up in a fix.

    We have no idea about the interconnectedness of the web of life. In the 1970s, it was discovered that the aspen tree was all but disappearing from Yellowstone in the USA and nobody could figure out why. When wolves were reintroduced, the aspen returned. Elk and deer eat aspen and willow shoots. Once wolves started bringing them down, the elk and deer would avoid the area of the kill, and hey presto…aspen and willow re-established themselves in those places. Who knows what our landscape would be like if most of the native animals of this land weren’t missing. Again, we decide what can and can’t live here, so there are no wolves or bears and deer are limited to allotted areas (usually by virtue of the reduction of forest and establishment of fences) and in prescribed amounts that those areas can support…on and on.

    Furthermore, plants have their own intelligence. I have two trees in my garden and their branches grow to avoid each other. Another tree’s branches grow nearly vertically on the side of the garden that adjoins my neighbour–who cuts away everything that overhangs.

    I agree wholeheartedly with RLM McWilliams and despair of our shortsightedness. We tell children not to pick flowers, not to damage the environment, while condoning the mass destruction of land–as long as it is easier to get from A to B and we have parking and shopping outlets or industrial parks once we get there. How many wild flowers are decimated in those processes? Yet, lay it on the children whose healthy development depends on the wonderment of exploring the natural world and picking as many flowers as they want to press in books or give to their mothers. Instead, we build more roads and frighten the kids with stories of endangered species and look at anything new that volunteers to live with us with suspicion.

    Shall we reject the bacteria that’s been discovered to eat radioactive particles and reduce those paraticles down to neutral compounds…as it’s not native to our area?

  9. Robin- excellent interview. It stimulated a lot of connections for me. I have been so weary of the battle cries here in the US by gardeners to eradicate japanese knotweed , oriental bittersweet and purple loosestrife. We place native species on pedestals without knowing that many are immigrants -often with their own “invasive”tendancies- but we’ve lived with them so long and have uses for them so forget they aren’t native.
    Here in the US the most egregious invasive species are us, the people who eradicated those people who lived here and then tore up the earth to plant monocultures. We have a lot to learn, and i think plants can teach us if we will slow down and pay attention.

    Here’s a technical suggestion for the podcast. You need to get closer to your Mike. Eat the mike, they say.
    Thanks. I look forward to more great topics.

  10. Himalayan balsam attracts alot of humblebees ,You must know how to prepare it ,for making it edible ,because the plant is slightly poisonous The young stems ,cut them off above the nodes ,then,by hand you can strip off the skin ,the taste is delicious cucumberlike ,also you can cook them ,what has been done in the himalaya where it is normal to do so The seeds have a nutty taste ,,make a kind of tahin of them with some echinacea-seeds to evoke your saliva ,To harvest them ,sow them inbetween 2 long peaces of root foil that will make it easy to collect the seeds that fell on the ground ,and by removing the folie after ,clean soil has been left !

    • I can find no reference in any of my Indian ethnobotanical books (I picked them up from the Forest Research Institute in Dehradun) of the stems or leaves being eaten, only the seeds mentioned. I’ve studied I. gladulifera for over 10 years. I certainly would not recommend experimenting with them raw as they are potentially high in calcium oxalates.

  11. As a conservationist “dinosaur” of 35 I’d like to add the following points Himlayan Balsam has a very shallow root that doesn’t bind the soil in the winter hence issues with erosion.

    I have seen Balsam take over woodland floors in the UK where you get plenty of other species growing. It can complete monopolise the vegetation ground cover out competing other plants for life. My understanding of ecology is more species in an ecosystem is healthier then fewer (even if the bees do love it). I’m also pretty certain that you are not meant to transport none native species in the UK , in actual fact I think it’s illegal. Doesn’t matter if you’re going to eat it!

  12. Deano – Thanks for your comments. You are not allowed to transport non-native species that are listed in Schedule 9 of the WCA for the purpose of sale… Note the word ‘sale’. I understand your fears and concerns, however I ask that you read and look at the new scientific thinking in the links above.

    You seem to have missed the bit about invasive species are thriving in areas that humans have disturbed. So maybe start asking yourself what practices do we, as humans, need to start changing to stop the spread of invasives?

    The point of the deliberately provocative podcast, was to get folk to ask this question. Most don’t, and still trump the same old message, while not answering the question. We are the problem. The science is showing that.

  13. Well… I have bought the recommended book and will read it as soon as it arrives.

    I have thought all of the above things over the past 40 odd years, ie my adult life, living in a steep valley where the Himalayan Balsam has progressively taken over huge areas where plenty of other plants were growing previously (it was not bare ground) and biodiversity has been greatly reduced.

    I have noted that the bees are drawn to the Himalayan Balsam – but then I remember that before there was so much Balsam there were plenty of bees feeding on the other plants that are no longer there, and in my memory there was a much longer overall flowering period when there were so many different plants growing. I could be wrong. And there are still areas where the Balsam doesnt grow – it doesnt grow on the moors and it isnt in all of the woodlands. But where it grows, not much else at all grows now.

    I have thought much about the Flower Remedies aspect over the years, and about plants showing up where we need them, and about Balsam being the Bach Flower Remedy for impatience. I have thought a lot about all this and it is all very interesting and worth thinking about and I just don’tknow a definitive ‘answer’.

    I have heard some people who have not lived here for so long talk about how good the Balsam is for bees – and I have noticed that they do not listen when they are told by other people who have lived here longer that where the Balsam now is (pretty much as a monculture) there used to be such diversity of flowers and the bees were plentiful then too. I have noticed that because there is now such a lack of variety, the bees actually have less to feed on outside of the Balsam flowering time.

    I have noticed that the Balsam has a very very shallow root and as such does not bind the soil at all, in fact it seems to leave the soil more loose than it was before, and I have wondered about the significance of this, given that this leaves relatively bare, loose soil in winter, vis a vis our increased flooding in recent years. I am well aware of climate change and changing weather patterns, increased building and hard surfacing on the land, management of the uplands in a way that has greatly reduced the sphagnum moss coverage local?y and probably nationally, many distinct and inter-related factors, and I wonder about the significance of the loose bare soil left in the valleys after the Himalayan Balsam dies down in this complex equation.

    So I am looking forward to this book arriving and will read it with interest and as open a mind as I can manage.
    I have read quite a bit on the rewilding debates in general and have not reached a position of definitely saying ‘this’ or ‘that’ is right or wrong.

    I found it interesting that in this debate there have been references to plant immigrants almost as if assuming that being concerned about losing a native biodiversity of plant life was somehow akin to being against people immigrating to this country, a political stance. In mind these are not connected.
    A very interesting discussion.

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