Some of my best plant combos have been what I call "happy accidents". Just had one this summer when I unloaded purchased plants from my car and happened to set down PowWow Wild Berry and Pretty Belinda yarrow next to each other on the sidewalk. I hadn't intended to plant them together, but when I saw them, I knew it had to be. And sometimes you just have to get a plant in the ground; you stick it in some random place, and it turns out to be wonderful!