Meet the plant taking 57 years to flower

16 July 2019

Interview with 

Alex Summers, Cambridge University Botanic Garden

AGAVE

agave leaves

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A giant agave plant at the Cambridge University Botanic Garden is preparing to flower for the first time in 57 years! It belongs to the Asparagus family, and the first hint of the flower appeared on the 19th June. Since then, the flower “spike” has grown a whopping 10 centimetres every day! Adam Murphy spoke to Alex Summers from the Botanic Garden, asking firstly what kind of plant agave is...

Alex - So tequila as a drink is actually fermented from sap taken from agave, a different species to the one we're growing here. We do grow agave tequilana and as you said it takes them a long time to reach a point of flowering. If we were growing it to make tequila, we'd actually cut off this flower spike because we want to get it as large as possible and then we take all the leaves off and it's actually the central crown structure that's actually baked and then fermented to produce the drink.

Adam - What does it look like? What would people see if they went?

Alex - They'd see a large rosette of leaves. So imagine a dandelion with very very thick leaves, and then amplify that up to about two or three metres in size, and then you'll be thinking about the sort of rosette that you're looking at with our current agave that's about to flower now. And then the structure coming out the top of it stands now at about 3.4 metres.

Adam - So that’s a metre above me at least?

Alex - It's absolutely huge yes. So it is well set for being in that desert environment where it really wants to advertise those flowers to as wide an array of pollinators as it can.

Adam - And why is it doing this now, why is it behaving like this?

Alex - Good question. So we've had this since the 1960s and it would have been planted in the house it currently sits in now, about 10 years ago. Prior to that it would spend most of its life in a pot. So probably what's happened is whilst it was in a pot the restricted root room meant that it didn't reach a size at which it could do what it's doing now, which is putting that flower up. So the agave is a plant which comes from deserts. And so what it does is over its life it builds up those limited resources until a point at which it can send up a massive flower spike. So whilst it was sat in our back reserve houses it never reached that point.

When it was planted out and it had the space it has now quickly reached the point at which it can flower and post that it will die.

Adam - And so there'll be no plant left, it’ll just be gone?

Alex - It's an interesting one, what can happen is it can reproduce vegetatively, so it can produce little offsets or pups, but its main aim is to produce lots and lots of seed

Adam - Do any other plants grow this fast or is this special?

Alex - It’s one of those situations where this plant's been putting a lot of energy and time into producing that flower structure in the very centre of the rosette. But there are many other plants that are able to quickly increase their size like that so if you come at the moment we've got our very large Victoria water lilies and those pads are up and increase in size over the course of a couple of days.

Chris - Alex can I just ask you a question because if this can defer flowering like this, until the time is right for that particular plant isn't that a bit of a high risk strategy. Because if you want to have sex with another plant you need another plant to be flowering at the same time and if they're all over the place in the desert and they've got a really ad hoc process like this, where most plants solve that problem by all flowering at the same time this is not going to happen.

Alex - I wouldn't say plants always solve that problem by flowering at the same time. I think that what you actually see in situations is plants have a fantastic opportunity, unlike us which is they usually produce male and female parts. So what it can do is it can self. It doesn't want to self. You're absolutely right.

Chris - Self pollinate?

Alex - Yeah. The pollen can produce seed from the same plant. That's not always the case but in the case of something like this it's obviously working on the situation that it grows in a massive environment and probably one of the drivers of evolution is that it is a huge ecosystem, which means that there is a likelihood that it's going to be in flower at the same time as another. It’s also setting up so it can present itself to organisms which are able to travel long distances. And that's why it presents itself probably at such a large size.

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