literally "not even a blade of grass grows"; describes land that is completely barren or infertile

literally meaning not even a single blade of grass remains, describing a scene of total devastation or destruction such as from a natural disaster or war

the deep kindness of one's parents is hard to repay; refers to the difficulty of a child's small heart (the grass) repaying the immense warmth of a parent's love (the spring sun).

(metaphor) a child's small heart or humble gratitude toward their parents, parents, as expressed in the famous poem "Yóu Zǐ Yín" (The Song of the Traveling Son) by Mèng Jiāo