The best things a gardener plants are the ones that keep coming back, and kindness is one of them. Getting your hands in the soil may even lift your mood. Researchers at the University of Bristol found that a common soil bacterium, Mycobacterium vaccae, activated serotonin-producing brain cells in mice, the same mood-related system many antidepressants work on.From a mother’s secret message hidden in a backyard full of mint to pansies planted in potholes, these stories show how a simple gardening hobby can grow kindness and happiness for everyone around it.