Lynn Castle never knew what the late John Fairey would pull from under his bed, dig from his closets or retrieve from the rafters when she visited his home near Hempstead. Fairey famously collected many rare botanical specimens from remote areas of Mexico during a few decades of plant hunting that began in the late 1980s. Over time, the acres he cultivated with those finds evolved into one of the world’s great conservation gardens. And plants weren’t all Fairey brought home. He was just as obsessed with Mexican folk art, amassing more than 600 pieces — way more than the private gallery next to his home could hold. When he…