What is the best way to request healing help from a tree? Can it only happen intuitively? Will talking to a tree out loud make any difference?

In general, this need only be an intuitive exercise. One can speak out loud and that could help the person focus and add greater intention in the same way that a spoken declaration carries greater force than simply thinking about doing something. It is crossing a line, it is coming out into the world in a very visible, tangible way compared to mulling something over and perhaps holding it as an ill-formed, incomplete thought. It is when there is strong desire being mounted that one speaks out, so it is the power of intention that really matters. Talking out loud is simply one way people can summon greater energy and put more intention into a communication, but those using intuition can do the same within their mind—it is a function of awareness, belief, and self‑discipline that is needed.