Answer:
A time when they're green. A time when they're brown. But both of these times, cause me to frown. But just in between, for a very short while. They're perfect and yellow. And cause me to smile.
It floats over the land, It cuts the tallest mountain, Its voice is like a fountain, Its body like a snake, Will flow into a lake.
What has 13 hearts but none beat?
I know a word of letters three. Add two, and fewer there will be!
I work when I play and play when I work.
What covers its face with its hands, speaks no language, yet most known what it's saying?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?