I, too, am more of a gardener in this metaphor than an architect. But GRRM notes that it's important to do some architecture along the way, and I totally agree with that. I won't outline an entire novel, but I'll outline a particularly complex scene or sequence of scenes. In general, though, I love to just scatter little plot ideas and notions here and there, and see which things come back as important things and which don't.
As I go back through the manuscript to Princesses In SPACE!!! (not the actual title), I am noticing a lot of those tiny little details that I just threw in willy nilly, and now some of them are striking me as having some potential down the line.
Writing is awesome!