Random Tree Generator

What the random tree generator does

You need a tree. Something for a garden plan, a species for a worksheet, a name for a street in a place that does not exist yet, a starting point for finding out what is actually growing outside your window.

Press the button and you get one.

What follows is a question that sounds like a child asked it and turns out to have taken science three hundred years to answer. Where does a tree come from?

How to use it

1. Choose how many you want. One if you are deciding, more if you are browsing.
2. Press Generate. A fresh draw every time.
3. Press Copy to take the set with you.

The man who weighed a tree for five years

Everyone in the seventeenth century knew where a tree came from. It came from the ground. You could see it happening. The tree was in the ground, the tree got bigger, the ground was clearly what the tree was eating. Plants ate soil. This was not a theory anybody argued about, it was a description of something obvious.

A Flemish physician called Jan Baptist van Helmont decided to check.

The design is so clean it is still taught. He took an earthen pot. He filled it with two hundred pounds of soil that he had dried in an oven first, so that he knew exactly what he had. He weighed a willow shoot: five pounds. He planted it.

Then he waited five years.

For five years the only thing that went into that pot was rainwater, or distilled water. No feed. No fresh soil. Nothing but water and time, and a man keeping careful track.

At the end of five years he weighed the tree. One hundred and sixty-nine pounds. It had put on a hundred and sixty-four pounds of wood and bark and root, and that was without counting the leaves, which had fallen off four times and which he freely admitted he had not bothered to weigh.

Then he tipped out the soil, dried it in the oven again, and weighed that.

One hundred and ninety-nine pounds, fourteen ounces.

The soil had lost two ounces.

Sit with the two numbers next to each other. The tree gained a hundred and sixty-four pounds. The ground it was standing in gave up two ounces. Whatever that willow was made of, it had not come out of the pot, and van Helmont had proved it with nothing but an oven and patience and the willingness to wait five years for a number.

So he was left holding the obvious question. If it did not come from the soil, where did a hundred and sixty-four pounds come from?

He looked at what he had put in. He had put in water. He concluded that the willow was made of water, and wrote it down: a hundred and sixty-four pounds of wood, bark and root had arisen out of water alone.

And that is wrong.

He had already named the answer

Here is where it becomes genuinely painful.

Van Helmont was not some gardener who got lucky with a pot. He was one of the most careful experimentalists of his century, and he had done something nobody had done before: he had worked out that air is not one thing. That there were different airs, with different properties, coming off different processes. He needed a word for them, because there was not one, so he invented it.

The word he invented was gas.

You are using his word. Every time anybody says it, anywhere, in any context, that is van Helmont's coinage, made up in the early 1600s because the concept did not exist and he had found it.

And he did not stop there. He identified a specific one. The one that comes off burning charcoal, and off fermenting wine, and off wood. He gave it its own name.

He called it gas sylvestre.

Gas of the woods.

It was carbon dioxide. He found it, he named it, he named it after trees, and then he grew a tree out of it for five years and concluded the tree was made of water.

He had both halves. They were in his own notebooks, in his own handwriting, in his own invented vocabulary. The willow and the gas of the woods, sitting on the same desk, and he never put them together, because his theory said everything was made of water and the theory was louder than the data. He even had a third clue and dismissed it: he knew that burning plant matter produced mostly gas, which is the entire answer stated backwards.

One historian of science, writing about this, worked out what it cost. If van Helmont had concluded that his willow was mostly made of gas sylvestre, he would have advanced plant science by more than a century.

He missed it by an inch, in his own vocabulary, for five years, on purpose, because he already knew the answer and the answer was wrong.

It took until the 1770s and after, with Priestley and Ingenhousz and the rest, for anyone to assemble what van Helmont had been sitting on the whole time.

What a tree is actually made of

Take an oak. Dry it out completely, so you are left with only the substance of the thing and none of the water. Roughly half of what remains is carbon.

Every atom of it came out of the air.

Not most of it. Not the bulk of it. Every single carbon atom in every tree that has ever lived arrived as a molecule of carbon dioxide, drifting past a leaf, and got caught. A pore opened, the gas came in, and light was used to break it apart and bolt the carbon onto a chain of sugar. Then that sugar became wood. That is the entire trick, and it is happening in complete silence, everywhere, all the time.

Which means the sentence at the bottom of all this is one that sounds like a lie and is a measurement.

A tree is mostly sky.

The oak outside your window weighs several tonnes, and it built almost all of that out of a gas so thinly spread through the atmosphere that it is measured in parts per million. It took the air apart, one molecule at a time, over a century, and stacked the pieces up into a thing you can lean against. The roots are not there to eat. They are there for water, for a handful of minerals, and to stop the whole business falling over, which is a real problem when you have made yourself that heavy out of something that weighs nothing.

Van Helmont was standing next to the answer for five years. What he actually proved, and could not accept, is that his willow had grown out of the air above the pot rather than the soil inside it.

Whatever this generator has just handed you, that is what it is. A large piece of sky, standing up.

Where these come from

The trees come from a list our team researched and checked by hand, so the names are real species rather than approximations. Your browser picks from them at random. Nothing you do here leaves your device.

Questions people ask

So does soil not matter at all?

It matters enormously, just not in the way people assume. The soil supplies water, nitrogen, phosphorus, potassium and a set of minerals the tree cannot make and cannot do without, and a tree in poor soil will show you exactly how much it minds. What the soil does not supply is the bulk. It is the difference between the ingredients that make up the mass of a cake and the pinch of salt that makes it work.

Was van Helmont completely wrong about water, then?

No, and this is the part that made his error so durable. A living tree really is mostly water by weight, so he was pointing at something true. His mistake was about the dry substance, the wood itself, and by not weighing the leaves and not accounting for his missing two ounces he removed the only evidence that might have argued with him.

How much carbon dioxide does a tree actually take out of the air?

It varies wildly with species, age and conditions, and any single figure you are given should be treated with suspicion. The useful way to think about it is the one above: look at a tree, estimate its dry weight, and about half of that is carbon that used to be in the atmosphere. The tree is the receipt.

How do we know how old a tree is without cutting it down?

You take a core. A hollow bit is drilled in horizontally, a pencil-thin cylinder of wood comes out with the whole ring sequence in it, and the tree seals the hole. Rings are annual in temperate species, so counting works, and because the widths track the weather each ring is also a note about the year that made it.

Is a palm a tree?

By any ordinary use of the word, obviously. It is tall, it is woody enough to climb, it has a trunk and leaves at the top. The technical answer is more complicated and mostly interesting to botanists, and if somebody stops you in a park to explain it you are entitled to keep walking.

Can the same tree come up twice?

Not within a single draw. Ask for ten and you get ten different ones. Press again and everything is back in play.

References

1. Hershey, D. R. (1991). Digging deeper into Helmont's famous willow tree experiment. The American Biology Teacher, 53(8), 458 to 460. https://www.jstor.org/stable/4449369
2. Encyclopaedia Britannica. Jan Baptista van Helmont. https://www.britannica.com/biography/Jan-Baptista-van-Helmont
3. Hershey, D. R. Misconceptions about Helmont's willow experiment. Plant Science Bulletin, 49(3). https://helmont1.tripod.com/hersheypsb49-3.htm