No pine grows in the flowerpot, and no eagle flies in the birdcage.

In a narrow environment, it is impossible to cultivate truly outstanding talents or things. This sentence vividly tells people that Pinus ponderosa is a tall tree species that grows in nature and needs vast land and plenty of sunshine and rain to thrive. The eagle is a bird of prey soaring in the vast sky. It needs free space and broad vision to show its heroism.