This is a Cherokee legend...
When the plants and trees were first created, the Great Mystery decided to give a gift to each different species. But first, there was a contest to see which gift would be the most useful to whom.
"I want all of you to stay awake and keep watch over the earth for seven nights," the Great Mystery told the plants and trees.
The young plants and trees were so excited to be trusted with watching over the earth that they had no trouble staying awake the first night. The second night was not so easy and a few of them fell asleep as dawn approached. On the third night, they tried to whisper to each other in order to stay awake but many fell asleep. On the fourth night, even more slept.
By the seventh night, even the beautiful larch had fallen asleep. The only plants still awake were the cedar, the pine, the spruce, the fir, the holly and the laurel.
The Great Mystery exclaimed to them, "What wonderful endurance you have!" "You shall have the very special gift of remaining green forever. You will be the guardians of the forest. Even in the dead of winter, your brother and sister creatures will find that life is protected in your branches."
And ever since that day all the other trees and plants lose their leaves and sleep all winter while the evergreens stay awake.