What has roots as nobody sees,
Is taller than trees,
Up, up it goes,
And yet never grows?
A Saturn V rocket.
Roots as nobody sees: All humans are born on and have mental roots to the Earth. They also have roots to Mission Control, who coordinates with the rocket to keep the astronauts safe from orbital debris. There's also the more physical roots to the Earth, since we all need food and water from Earth.
Is taller than trees: Standing at 363 feet tall, the Saturn V rocket is taller than all but the tallest of terrestrial trees.
Up, up it goes: I think this part should be obvious. It's an orbital rocket, it rockets to orbit.
And yet never grows: A Saturn V rocket sheds most of its mass, both in the form of rocket propulsion and in staging, as it flies up into orbit. It doesn't grow, it shrinks.
