Which word in stanza 2 is opposite in meaning to ‘the frost’?

The word 'frost' in stanza 2 differs in meaning with the word 'grassy'. Frost has a chilly reference which means a degree or state of coldness sufficient to cause the freezing of water. This meaning lacks a green live feeling which is present in the word 'grassy'. Grassy means something which is like grass or pertains to grass.