Light! This is your most urgent need. You stretch your branches out as far as you can, wrestling your neighbours out of your way. You pump nutrients up your stem as fast as you can, feeding another leaf bud at the very top of your crown. Just one more inch. Just one more! Then you’ll be the tallest one around.

It is costly to be a giant: you need more nutrients than a small organism, and you’re heavy and less nimble. But, in the right circumstances, casting a large shadow can be a huge advantage. You’re dominating the landscape, soaking up the most water and nutrients. If predators abound, you’re more likely to fight them off.

Why did you get so huge?