C (2:58)

Lovely. That's a very helpful introduction. How then did this book come to be?

A (3:03)

So this is a. This is a book that was basically suggested to me by the. By the editors at the Bodleian. They wanted me to. They wanted me to write another book. And this is al. And this is a subject I've been thinking about for years, basically, since I was. Since I was an undergraduate, when I was first introduced to. When I first started to study biology, started to think about these things in detail. It's something I think about. I thought about quite a lot in terms of just how many plants you actually come across in your daily lives and how we just completely ignore them.

C (3:50)

And so now you've gotten to kind of put all of that thinking into one place. The obvious question then is, 50 plants to change the world. How did you choose which 50? Was it hard to come up with 50? Was there a lot you had to cut out? Like, how did you go about getting to that number?

A (4:07)

Right. So we interact, we exploit, if you like, about 35,000 plants. That's about 10% of all of the plants on the planet. And so, you know, getting from 35,000 down to 50 is quite a challenge. So I thought about it in terms of my own experience, which is obviously within a Western context, so that narrowed narrow things. I also thought about it in terms of the plants that people are familiar with, because I could have made this. I could have made this list. A whole range of things that people really don't know, they come across in their daily life, they're not really that familiar with. So I ended up with a list of about 300 in terms of a short list. And then I paired this. And I went through the process of. Of paring this list down in terms of which plants represent different ideas, they represent different parts of the world, they represent different times when these things happened. And also some of the plants that have really good stories associated with them, obviously, as well. And then I also threw in a few things that people are unlikely to be so familiar with. But I have been really important in terms of the. Particularly in terms of Western civilizations, at least our thinking about plants. And then I ran my sort of list of 50 through or I asked colleagues to come up with a similar list of. Asked about 10 people. And I was really pleased that more than half of the plants that I had had on my list were on their lists. So we were thinking in similar sorts of ways. And then the other. The other plants are really represent our own idiosyncrasies and obsessions, if you like.

C (6:17)

I found that part of the book quite amusing to think about. Sort of, you know, everyone's going, oh, yeah, okay, that makes sense. Well, hang on, what about my personal favorite? Right. And of course, it is always that comb of the personal and the general that make up these sorts of lists. So thank you for telling us about the process that you went through to come up with this group. Within that, then, of course, there was a whole bunch of research and writing that you had to do to kind of tell us these great stories about the plants after you'd selected them. Were there any plants in particular that were maybe kind of came immediately to you or ones that were trickier to either research or figure out how to tell a story about?

A (6:53)

So the ones that really came easily are the sort of. Are the big ones that you might expect, things like wheat and barley, potatoes, chilies, these sorts of things. The ones that were more difficult were. It was not necessarily the research that was more difficult. It was actually trying to write about them in a way that would engage people and also wouldn't be repetitive of things that perhaps had come earlier. So I think we may talk a little later on about this thing called Fail Press, which was. It's. It's a really important plant, but it was really quite a challenge to try and make that engaging, I think, to people.

C (7:55)

Yeah, I can imagine that some of the things, especially the ones we take more for granted, would kind of need a bit of exposition to be like, why is this even in here? And then let me tell you the story, sort of two tasks in one. Yeah. One thing that I noticed across a number of the plants you discuss in the book was discussions around the origins of them. And. And this is obviously something we talk a lot about when it comes to material objects. You know, when was a particular, I don't know, style of vase created or whatever? How did language develop over time? How do we figure out the origins of specific plants? Is this kind of something we can generally do? I would have assumed that the assumption, the general way this would happen is kind of it's a plant that exists in the wild, and then humans change it in various ways. But is that actually something that is A, true or B, figureoutable?

A (8:44)

So in some cases it is figureoutable, and in other cases it's much more difficult. So it's not. It's an accumulation of evidence. So it is not the case that you can look at something and say, ah, right, that's that must be the wild, wild relative of, of that thing. So it's an accumulation of evidence based on morphology. So that's the idea that if things look very similar to, in the wild, to things that are being grown in, in our gardens, then perhaps they might be related to each other. There's also the idea of where they, where they occur. So where these plants, do these plants actually grow in areas where, where people are found and people have been found historically, do they occur within archaeological contexts? Are they found within prehistoric deposits? Increasingly and particularly in the last 20, 30 years, then that's come down to a lot of that has also come down to DNA. So do we have the evidence from DNA that these things are actually closely, are closely related to each other? And of course, sometimes these origins are really very complicated. It's not simply the case of finding, if you like, a species in the wild and then bringing it into domestication through some process. A lot of this was obviously done subconsciously, was done. And people, you know, a lot of this happened when people didn't really know precisely what was going on. And so, you know, nature was doing, was, was, was doing their stuff. You were getting, you were getting crossing going on between species. You're getting hybridization. People were seeing things that they liked, they particular features that they might have liked and think, oh, well, that's really nice, I'll bring that into my garden. And so we can have some really very complicated origins. So, for example, wheat, domesticated wheat that's got at least three different species from the near east actually involved in its origins. In some cases we have, we have a domesticated plant and we know where the domestication is likely to have happened because that's where all the archeological deposits are found. So, for example, the broad bean. But the broad bean is very different to any of its wild relatives. And then that raises the intriguing question of precisely how did that domestication happen? Is it a case that the wild relative has actually gone extinct so we can no longer see it? So we need to also take into account those types of things. And then there's also other sources of evidence might, for example, include looking at common names, looking at a language, looking at how names change over time. And this may give us a clue as to what we might be looking at or what we might be looking for.

C (12:27)

Really interesting to understand kind of all the different places that one looks to figure this out and kind of the detective work to bring it all together. Thinking then about some of the ways these plants have been used at different points of the historical record. I wonder if we can discuss plants in forms of worship or as part of religious practices. You have a few different examples in the book. Can you tell us some?

A (12:53)

So plants have been very important within the context of people's lives, and a really important part of people's lives is obviously within the religious context. So we can look at very large number of world religions and they all include plants within some element of their worship, often within having symbolic meaning. We can think about. We can think about bread and therefore wheat. We can think about wine and therefore grapes within the Christian context. And so you find similar relationships within all sorts of religious contexts. And that's not a surprise, given how important plants are within people's lives, how important religious systems can be within people's lives, and particularly within the formation of societies.

C (14:00)

Are there any particular plants that have this sort of history that you'd like to tell us about?

A (14:05)

Yeah, so, for example, one of the ways in which plants can be incorporated can be thought about within this context is how past religious practices have been moved into contemporary religious practices. So, for example, we might think about religious festivals. So one case again within the Christian context would be the Rogation period, which is that period where the bounds of an area are defined from a religious point of view. It's a boundary, it's associated with a festival, the beginning of spring, and that has its origins actually within the Roman religious festival. So the 25th of April would be Robbigallia, which is exactly the same type of festival that was used within the Roman context. And so we see these things appearing very frequently.

C (15:27)

Yeah, I found that a really interesting example of kind of continuity over time, even when so many other things change. And in fact, there was another plant I'd love to ask you about in a similar sort of vein, given that the mandrake is still linked to sort of witchcraft and magic today. I'm thinking, for example, of its appearance in the Harry Potter series. But how far back does that association actually go?

A (15:50)

Yes. So mandrake's one of these plants that have got this huge folklore associated with them. And we can think about this folk. We can think about this folklore in terms of going way back in time, Secretary back into, as far as written records, certainly within Western cultures, go into Sumerian and into the Egyptian manuscripts they are using. There are references to mandrakes. There are references to the use of mandrakes within religious practice, also for the medicines and, of course, mandrakes themselves. One of the reasons that mandrakes are people are so strongly associated with, with mandrakes is obviously the form. So they have these roots which with a degree of imagination can take on the human form. And they look like, they look like humans. As humans, we're extremely good at seeing patterns within, within nature. And you can see a human form in that, you know, human form associated with a plant would give it perhaps a particular significance, particularly with the later idea of the so called doctrine of signatures. And the other aspect of that, when you combine that form with the fact that it is biologically extremely active on humans in terms of both as a medicine, a hallucinogen and a poison, all of these things combine to make it a very. A plant that people will strongly associate with all sorts of activities. And the other thing about it, of course, is that it's one of these plants that for most of it, for most of the year it's underground and then it just sort of the leaves appear, the flowers appear, the fruits appear and then it disappears. And this thing seems to sort of be popping up as well.

C (18:24)

That's really interesting to hear just how far back that goes and how persistent it is across different cultures. Thinking then about a plant that maybe doesn't have necessarily super strong kind of popularly understood connections. Can we talk about the sugar beets, which is, as you discuss in the book, still quite an important industrial crop. That's probably more in the category of overlooked plants. And tell us about why this particular plant has strong associations with Napoleon and France.

A (18:54)

Right, yes. So sugar beet. Sugar beet is, is a source of. A very important source of sugar. When we think of sugar, we often think of sugar cane, which is a species that's grown within tropical regions and of course very strongly associated with colonialism and slave trade. But the sugar beet is a species that is, is grown in temperate regions. And sugar beet looks, it looks very similar to beetroot, except it doesn't have the strong red coloration. And of course, one of the reasons that people consume large amounts of beetroot on stage was because it's got a very high amount of sugar in it. It's very sweet. So. But sugar beet itself is one of these species that becomes important essentially during the 19th century. And this is then, this is through the realization that it is a source of sugar. It is an important source of sugar. And of course, sugar is something that we as humans crave. We've got, you know, there's a massive amount of sugar and sugar consumption. It's. And then, so during the Napoleonic wars, with the blockading of the Caribbean, which was the main French source of, of sugarcane. The, the French had a problem, and that problem was where do they get their sugar from? And in Germany, in northern Europe, they were growing a. They'd started to grow a crop and develop this crop. Sugar beet, which is its wild relative, is actually a plant that you find very commonly at seaside and has been used as a food plant on the seaside for at least 7 to 8,000 years in northern Europe. But it started to be grown in northern Europe as a beet crop. The sugar levels were not very high. But gradually people started to apply selection. They started to collect seed from the sweetest varieties and then they, they grew those. And this type of thing, we now understand this is a form of artificial selection. And through that process we, we ended up with these, with, with sugar beets. And so there was then this great push by Napoleon to take on this northern European crop and to force essentially French farmers to grow sugar bit for sugar production, for industrial sugar production. And as soon as that started to happen, then people started to see the advantage of, of being able to grow, to have this sugar crop grown in temperate regions. And the other thing that of course this plant is important for is as animal fodder.

D (22:41)

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C (25:10)

Really interesting to be able to trace back such a big change to a particular moment, especially in contrast with some of the plants you were telling us earlier that kind of continue throughout the rise and fall of different political regimes? Thinking about some other plants in the book that kind of also have more, I guess, rise and fall type things. Are there other plants you talk about that used to be a really big deal, but are maybe less so today or the other way around? Some plants that maybe are newly important for civilization today.

A (25:41)

Yes, yes. So it's not a surprise that plants go through this process of rising and falling in popularity. We see it all the time. But there are certain plants, for example, that we can think of in the 14 1500s in Europe were really, really important. Woad, for example, which is a source of a blue dye it grows, it's produced through a rather unpleasant or at least a very smelly process of fermentation of this cabbage like plant. And Woad is one of these species that actually can competes with with land for human food production. It requires very high, very fertile land in order to be highly productive and but the value of the crop was such, at least the value of blue dye was such that it. People really didn't really had to make that decision between growing food plants or growing this industrial, this industrial blue dye. But of course over time what has happened is that these natural dyes like woad indigo for example, other sources were discovered. So for example another source was discovered in the 18th century from a tropical legume, a member of the pea family. And this is the indigo plant that we hear, we, we, we hear about growing for example extensively in India. It's really important in terms of the, the activities of the East India company in the 18th and early 19th centuries. And that was, that was again a source of. That was the indigo. So the, so if you like the chemical is the same but the source changes. So woe drops out of favor. Indigo comes, the indigo legume comes into favour and then it drops out of favor again with the discovery of artificial pigments and the chemical production of artificial indigos. So that would be an example of a plant if you like, that's gone into, gone into decline. But on the other side of that there are other plants that have become really important. So I suppose one of the, one of the big examples of that would be rubber. Rubber is, is a, is a latex which is found in a whole range of different, different species. But industrial rubber today is produced from an Amazonian tree and this. But until the, the middle of the 19th century rubbers were just a sort of bit of an oddity. They, they didn't really have that much, that much use. They were often difficult to get hold of and, and they had these odd properties that were really rather unstable. But people then discovered that they could stabilize these, they could change the properties of rubber and they could also do all sorts of things with it. And that is then associated with the start if you like of industrialization. So for example we have the production of welt rubber tires associated with, with motor cars and rubber seals. All of this type of thing which then required the introduction of. Of rubber plants, rubber treat into cultivation and there's a really big push for that. Another example of a plant that whose properties were known for a very very long time and value was known for a very very long time is soya. So in China soya is a plant that's been cultivated for thousands of years. But in terms of the west it's only really become important in. Well, it started to become important beginning of the 20th century when people discovered that the oil in soya could be modified, changed to form some. Some particular sorts of plastics which became useful. And then with it was also discovered that it could be a very significant source of protein and particularly animal protein for industrial production. Industrial, agricultural systems.

C (30:57)

Those are some really great examples. Thank you for sharing them with us. Another plant that I wonder if we can talk a bit about is one that maybe people have been seeing more, not just in terms of the season, but in terms of sort of icons and posters and flags. The sunflower is a big symbol for Ukraine and perhaps therefore has been more apparent in the last few years. You discuss in the book that the sunflower is also quite important in Russia. Why is this plant a big deal for these two countries?

A (31:28)

Right, so sunflowers are the. Are a North American species. They are a species that was. That was domesticated by. In North America. And the seeds and it's the. Well, it's the seeds and the fruits that are really important in sunflowers. And these were. In the 19th century, seeds of these were moved into Russia and into the. And into Ukraine, Eastern Europe. And one of the things that happened there was that people really took to them as a food plant. That hadn't happened in North America outside of the Native American communities, but in Ukraine, Russia, they really talked to them as a source of edible oils. And edible oils are really important, but they're also quite difficult to grow. The other reasons are the associations with again, the religious associations in that it was agreed that in fact, under the Orthodox Church that sunflower oil didn't constitute an oil in the sense that it would be forbidden, for example, at Lent. So it becomes a. Becomes a plant, a food source that can be used throughout the year. The seeds themselves are easily stored. And the areas of Russia and Ukraine where these plants grow, the great flat areas where they're easy to actually cultivate. And what was more important is that.

C (33:43)

The.

A (33:46)

Russian scientists and Ukrainian scientists got involved in breeding these and they bred these sunflowers. They dramatically increased the size of the seeds and also the quality of the oils that were produced. And it's these seeds which were then in the 1950s, were then moved back into North America and become the foundation of the North American sunflower industry, industrial sunflower production. So much of that breeding, plant breeding happened in Russia and Ukraine. The material was moved then back to its original homeland, if you like, for exploitation.

C (34:50)

That's quite a cool story of movement there. Thank you for sharing it with us. Obviously, there are plants like the sunflower in the book that are quite well known, even if that kind of backstory isn't as much, but we did mention earlier that some of the plants you've included in these 50 are not particularly familiar by name at all. So can you tell us about why you chose to include plants like lycopods or thalecrest?

A (35:16)

Right, yes. So lycopods, Lycopods are, and it's an odd group. The, the name, it's, it's a very, very old group of plants. They are relatives of things like the ferns. And lycopod actually means wolf foot and it's a reference to the, to the shape of the tips of the, of the shoots with the reproductive structures on. If you've got a bit of an imagination, they look a bit like wolf's feet. And, but the, the lycopods that we see today are really quite small. So in the uk, we've got, we've got four or five species of them. And they're, they're, they're, they're relatively small. They're probably no more than about 20, 20 centimeters tall. However, you go back into prehistory and into the fossil record, these things are enormous, you know, 10 to 20 meters tall. These, these lycopods. And the reason that they're in the book is that the, the, these lycopods are in fact, the, the source of coal. They, they fossilized lycopods are coal. And coal has obviously been incredibly important in terms of industrialization, in terms of the creation on Western economies, but also in terms of some of the environmental issues that we're facing today. And so, if you like, when we burn coal, we're burning lycopods, but we're burning the carbon, we're releasing the carbon dioxide that These lycopods photosynthesized 300 million years ago and adding that into the atmosphere. So that's the reason for including lycopods. There are a few modern uses of lycopods. So, for example, the spores of lycopods are often used in theatrical flash powder. They, if you throw them into a flame, you pass an electric charge through them, they will explode with a big flash. They were early part of early photography. They were also an important part of early photocopiers. And they're also used as a lubricant in some rubber products as well. So they do have the modern use. But the, this other plant that we have, this thing called Thale Crest, this is the final plant I talk about in the book. And this is a plant for which there's no, there is no historical, there's no prehistoric record of it. People don't use it. It's a. It's a tiny little. It's tiny little thing, even a big one only will probably get to about 20cm meters tall. It's a relative of the cabbages, as the name cress suggests. And the reason that it's there is because this is the plant that was chosen as the model plant for understanding biochemistry, genetics, cell biology of plants. And it's the plan for which the first complete genome sequence was produced. So we probably know more about the biochemistry, molecular biology, genetics of thalecrest specifically than any other plant on the planet. But what we learned from that plant, it can then be used in order to understand other plants within all of the other. All of the other plants. So. So that's the reason for including thalecrest, not specifically because it has a direct use for us, but for what we can understand about plant biology in order to apply that to other plants that we might be more familiar with.

C (39:34)

Yeah, that's a pretty compelling reason why it's important. So thank you for revealing that for those of us who are less expert. Expert in that particular plant. Staying then, on the theme of sort of why you chose to include certain ones that may be less well known. The last plant I'd like to ask you about in that vein is actually pretty well known, but may not be thought of as sort of quote unquote, worthy of being included in a list like this. And that's because ragwort is usually thought of as a weed. Why is it part of the book?

A (40:06)

Right, well, well. And the reason for including ragwort is because it is representative of, if you like, a weed and invasive plants, plants that we, for example, we move around, we change habitats so that plants move into, they compete with our activities. They have become really important. They are one of the big environmental things, threats that are faced by natural communities. So that was the reason for including ragwort. The other reason for including ragwort is it happens to be within a genus that. Within a group of plants that I've done a lot of work on. And so it's also a plant that's quite close to my heart in that respect. So this is one of my, if you like, idiosyncratic choices. Ragwort itself is very familiar to in the British landscape. It's got a very bad. And also in parts of North America and in parts of Australia as well, it's got a very bad reputation because of some of the toxins that it contains. Particularly if those toxins, those plants are eaten by livestock. So for example, in horses, it can. These toxins can produce liver cancer, which leads to a condition in horses called staggers. And so it's one of these plants that people get. Get very worked. Worked up about and it has a direct economic value. So essentially it makes, it can make highly productive grazing land completely useless for, for grazing and particularly for hay production. Because one of the things about, for example, with horses, one of the things is that if horses are in a field and they will tend not to graze ragwort, if there's ragwort in the field, but if that field is used for hay production, I either put the vegetation is cut down and then dried and then given to animals over the winter, then they will eat it. And one of the reasons for that is because the biochemistry changes and with drying, ragwort becomes very sweet. So there would then be. There's then a tendency to. For the animals to consume that preferentially. So it is a real, it is a real problem in that context.

C (42:46)

Definitely important enough to be part of this list. I have now just a final question about the plants, though. One more quick question after that. You've been doing so much in this conversation to reveal to us stories that we were not aware of, which is fascinating. Historical work. History can also be used to bust some myths as well. So for my final question, do bananas grow on trees?

A (43:13)

Interesting question. Interesting question. So people often talk about banana trees. So we need to, we need to think about what is a tree. Tree is a. It's quite a tricky. It's quite a tricky question to. A tricky thing to define in that there's. There's not a specific definition. Definition of a tree. But we can think, when we think of trees, one of the things that we think of is the fact that they're woody, I. E. That, you know, that they are. That they're durable. They produce a particular type of tissue called xylem, which is where water moves and they're tall. So if we look at bananas, then what we find is that, yes, banana plants at all, but they don't produce wood. What we are dealing with in terms of a banana plant is in fact a giant herb. So what you need to think about in terms of the thing that you look at as a banana plant is to realize that the stem of the plant is actually ground level or underground. And what you're seeing that are sticking up are in fact the leaves. And they are very, very untool leaves. And the thing that looks like the trunk, if you like, of the banana plant are in fact a whole lot of the stalks of the leaves all wrapped around each other so that you form this very dense structure, which superficially looks like a trunk. However, if you cut through looks completely different to a trunk, you can see that in fact, it is a whole load of leaf bases that are overlapping. It doesn't have the structure of a tree. So bananas do not grow on trees.

C (45:22)

What a great fact to end our conversation with and leading me to just ask the final question of what you might be working on now that this book is out in the world. Any current or upcoming projects you want to give us a sneak preview of?

A (45:36)

Yeah, I do all sorts of. I do all sorts of things. One of the things about my. It makes my job so fascinating. So at the moment I'm working on a book that's actually looking more specifically at collections and herbarium collections and trying to address the question of how important these specimens are and have been to the development of our ideas about plants. And, you know, so it's not just the ideas of, of how these plants were collected, this type of thing, but it's actually how the specimens have been used in order to generate knowledge, to generate understanding of plant diversity, plant evolution, how we use plants, how we might use plants in the future, how plants are changing their distributions, all of these types of things.

C (46:37)

Well, that certainly sounds very interesting. So best of luck with that project. And of course, in the meantime, listeners can read the book we've been discussing titled 50 Plants that Change the World, published by the Bodleian in 2025. Stephen, thank you so much for joining me on the podcast.

A (46:52)

It's been a great pleasure. Thank you very.