what causes trees to split? Do they just decide at 5 feet to say fuck it Imma head out?
In: Biology
At least for some trees, there are special cells (apical meristem) at the end of a stem. These cells produce a chemical (auxin) that stops other stems from branching. As the stem grows long, there is less of that chemical so other stems start to branch off.
The first stem a tree has is the trunk. So after the tree is tall enough, a new stem branches off and the tree starts to get wider at the top. This happens again and again over time.
As it grows taller, the older stems get bigger around to help support the weight. This is able to happen because the tree keeps its food and water movement cells just under the bark. Over time, these cells are made more rigid with other chemicals and new food and water movement cells grow on top of those.
This is why we see rings when we cut into a tree also. This process usually happens on a yearly cycle, so we can often count those rings to know how old the tree is.
This is important to your original question because those special chemicals from the ends of stems are pushed around by the food and water cells. That affects how much of the chemical is in any part of the tree and isn’t a perfect process.
Since this is ELI5, I’ve definitely oversimplified. Someone linked a post in r/askscience that has the more technical names.
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