I feel like an idiot but where do you find scaletree vine? I don't even know if I'm supposed to have found some before the "mini boss" or if I was supposed to beat him with no weapon and vines are in a zone past him or something.
You can find Scaletree Vines before the first "miniboss". They're found wrapped around slender trees, trees that are usually stood alone. Make sure to interact with them to gather them!
There's at least two areas they can potentially spawn in before the "miniboss", and some fixed locations will be available after defeating said miniboss too.