This black and white came from a vivid color shot of a Japanese maple at Portland Japanese Garden. I used only Lightroom.
After making basic tonal adjustments, I used the adjustment brush to bring up the sunlight at the base of the tree. I then converted a virtual copy of the image to black and white.
Using the B&W tone sliders, I boosted the red and orange to lighten the leaves, turned down the greens, and almost eliminated the blue channel.