Answer:
The root tops the trunk on this backward thing, that grows in the winter and dies in the spring.
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see.
At the sound of me, one may dream or stamp their feet, At the sound of me, one may laugh or sometimes weep.
It is an arctic double breasted formal wear.
You use it between your head and your toes, the more it works the thinner it grows.
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