When Linda Lee was young and living in the heart of Hong Kong’s urban metropolis, her father found peace in a small cluster of greenery in their flat. He stood in the corner each day, tending to each pot. When he smoked, he always turned to blow the smoke onto the plants, which would absorb the chemicals, he said, leaving clean air for Lee and her mother. Lee’s father was a tough character. He did not talk much, or have many friends. But Lee saw something in his face relax whenever he tended to...