Jenny McElwain

speaker

162 appearances 1 recordings 1 series first heard Jul 2026 last heard 2 Jul

Jenny McElwain’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 1 in all, peaking in Jul 2026 with 1.

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In Our Time · The Evolution of Trees · 2 Jul 2026 podcast

Yeah, that's actually such a hard question because we have to define a tree without using the word tree.

So there is actually, there's a lot of arguments and discussion among plant scientists about what a tree is.

But what we can say is that it has to have a trunk, so a main stem, and it has to have a canopy.

And the canopy, we think, usually has leaves today, but not necessarily.

So it is a canopy of branches.

that trunk has to not die back.

So we have structures that look like trees, but they're actually flowers.

So it means that it's a perennial structure, so that it will last for many, many years and not just die after one or two years.

And then to be a tree, the trunk and the crown have to be self-supporting.

So what that means is that this beautiful organism can't rely on leaning on a wall,

or before walls leaning on another tree or leaning on other vegetation.

And then other people use a definition of a particular height and a particular width.

So there's loads of arguments about that.

But I think a good definition is a tree has to be above three metres.

And then if you took your hand and at chest height measured the width of the trunk, it has to be wider than your hand to

Classify as a tree.

And then the big controversy comes with wood.

Yes, we absolutely can have trees without wood.

Some botanists are really strict and they say you can't be a tree unless you have wood.

But I think that's far too strict.

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