I'm 50-50, and there wasn't an option for that.
I know the characters, the premise, the main twist(s) and the ending, but I make up the details as I go. Something else that happens is that sometimes I plan a scene a certain way, and when the characters get there they have different ideas. I follow along.
Still, I start with a general idea of the whole plot, but it's super loose.
I don't know how some people simply start writing, from a scene, for example, and make up as they go along. I think I need to know that I material for a story.
I've studied plotting and structure, but I haven't tried to outline a story according to structure. I might try and see how it goes.
That said, once I decided I'd plot a novel in details. I think I have some ten handwritten pages with unreadable, weird notes, and I've never started writing it.
You guys mentioned GRRM, but the truth is that the stuff that he had outlined (we saw in the leaked outline) was really good. Anything beyond that got kind of lost.
I find the analogy with gardening very weird. Gardening requires a lot of planning. If you just let stuff grow it's going to be horrible.