One of my grammar leeches is とする (and sometimes the particle に, which seemingly does whatever it wants until I figure out what it means in a given sentence).
I think I know everything there is to know about とする but sometimes it throws me off. I know ～ようとする、Noun + とする, Noun + とする + Noun and Noun + とした + Noun and their diferences (I had to read an explanation in Japanese for that), etc, but the とする in the following sentence stunned me.
青々としている樹木。[The definition of 青木 when it does not refer to the tree itself but a kind of tree]
Can someone explain me why とする here, and specifically why the いる auxiliar?
I understand it as a quoting particle と plus する. If it’s している then it describes a state.
And depending on what you attach in front of と it’ll define the meaning. It’s often used with onomatopoeia for example. In this case it’ll mean the subject is in the state described by the onomatopoeia.
“A fresh and green tree”.
Subject: 樹木
Clause describing the subject: 青々としている
Verb in the clause: している - describes a state of the subject
Adverb: 青々（と）literally “how the している-ing is performed”, but it’s easier to translate as an adjective in English
Another answer is (less satisfying) :
it’s using とする because it’s a する 副詞
Yeah, the example above is not an idiomatic とする like the one in things where it means “to regard as.” This is just an adverb that takes the particle と and する expressing appearance. It’s と + する, rather than what I would consider “the とする grammar point.”