aeh, you're right, my question was rather unclear. I apologise.

I think what meant was:

If you have a noun, for example 'tree', can you say that something is 'treelike', 'untreelike', 'treeish'? Or is this totally incorrect use of the language?

I suppose my real question is: what are the rules for the nouns that can be turned into adjectives?

It's staring you in the face.