Tea tree oil, conditioner or shampoo?

I've been doing a lot of research on tea tree oil, and I like what I hear about it. I'm planing on buying it in it's natural form for my hair, scalp mostly cause I have a very troublesome one. I wanted to know if it was okay to add it to either your shampoo or conditioner, most people say your shampoo but I wanted to know if I had an option to add it to either one. I just thought that it might be more effective in conditioner since you don't wash it all out, it would still be some left in your hair. but that 's why I'm asking because I want to use it properly.