Answer:
The root tops the trunk on this backward thing, that grows in the winter and dies in the spring.
Hoofed frolicking.
The more of them you take, the more you leave behind. What are they?
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
What hangs others yet can unintentionally hang itself?
You use it between your head and your toes, the more it works the thinner it grows.