What is the tallest kind of tree?

Coast redwoods pass 115 metres, and the tallest known individual, called Hyperion, was measured at just over 116. Its location is kept secret, and the trail to it was closed with the threat of a fine after visitors trampled the root zone - a tree that survived two thousand years was being damaged by people coming to admire it.

There is a ceiling and it is close. Water has to be pulled from the roots to the leaves in unbroken columns held together by the cohesion of the water itself, and above roughly 120 metres the tension required would tear those columns apart. Measurements on the tallest redwoods show the topmost leaves are already water-stressed and shaped differently from those lower down. The tree is up against physics, not competition.

They cheat a little by drinking from the air. Coast redwoods live in a narrow fog belt along the Californian coast and take a substantial fraction of their summer water directly from fog condensing on their needles - which is also why they cannot simply be planted somewhere more convenient.