As far as I know, poetry can and often does break some limits of sentence and word structure if it is required by its rhythm or rhyme. I am translating one, and the perfect ending of a line would be the word "greening" in the sense of "being green", "having green leaves". The question is whether it is grammatically correct to say that "a tree is greening" because personally, being not a native speaker, I haven't met such an expression. Most websites (for example, https://dictionary.cambridge.org/amp/english/greening) provide the meaning of the word "greening" similarly to the following:
The process of becoming more active about protecting the environment
Or one of several sorts of green apples.
However, https://www.merriam-webster.com/dictionary/green#h1 provides a couple of meanings of "to green" as a verb:
To make green To become green
So "greening", as a gerund form of the verb "to green" could be used in my context, couldn't it?